Heligmosomoides polygyrus bakeri Infection Decreases Smad7 Expression in Intestinal CD4+ T Cells, Which Allows TGF-β to Induce IL-10-Producing Regulatory T Cells That Block Colitis

Helminthic infections modulate host immunity and may protect their hosts from developing immunological diseases like inflammatory bowel disease. Induction of regulatory T cells (Tregs) may be an important part of this protective process. Heligmosomoides polygyrus bakeri infection also promotes the production of the regulatory cytokines TGF-β and IL-10 in the gut. In the intestines, TGF-β helps induce regulatory T cells. This study used Foxp3/IL-10 double reporter mice to investigate the effect of TGF-β on the differentiation of colon and mesenteric lymph node-derived murine Foxp3^- IL-10^- CD4⁺ T cells into their regulatory phenotypes. Foxp3^- IL-10^- CD4⁺ T cells from H. polygyrus bakeri-infected mice, as opposed to T cells from uninfected animals, cultured in vitro with TGF-β and anti-CD3/CD28 mAb differentiated into Foxp3⁺ and/or IL-10⁺ T cells. The IL-10-producing T cells nearly all displayed CD25. Smad7 is a natural inhibitor of TGF-β signaling. In contrast to gut T cells from uninfected mice, Foxp3^- IL10^- CD4⁺ T cells from H. polygyrus bakeri-infected mice displayed reduced Smad7 expression and responded to TGF-β with Smad2/3 phosphorylation. The TGF-β-induced Tregs that express IL-10 blocked colitis when transferred into the Rag/CD25^- CD4⁺ T cell transfer model of inflammatory bowel disease. TGF-β had a greatly diminished capacity to induce Tregs in H. polygyrus bakeri-infected transgenic mice with constitutively high T cell-specific Smad7 expression. Thus, infection with H. polygyrus bakeri causes down-modulation in Smad7 expression in intestinal CD4⁺ T cells, which allows the TGF-β produced in response to the infection to induce the Tregs that prevent colitis.

Downregulation of the Syk Signaling Pathway in Intestinal Dendritic Cells Is Sufficient To Induce Dendritic Cells That Inhibit Colitis

Helminthic infections modulate host immunity and may protect people in less-developed countries from developing immunological diseases. In a murine colitis model, the helminth Heligmosomoides polygyrus bakeri prevents colitis via induction of regulatory dendritic cells (DCs). The mechanism driving the development of these regulatory DCs is unexplored. There is decreased expression of the intracellular signaling pathway spleen tyrosine kinase (Syk) in intestinal DCs from H. polygyrus bakeri-infected mice. To explore the importance of this observation, it was shown that intestinal DCs from DC-specific Syk(-/-) mice were powerful inhibitors of murine colitis, suggesting that loss of Syk was sufficient to convert these cells into their regulatory phenotype. DCs sense gut flora and damaged epithelium via expression of C-type lectin receptors, many of which signal through the Syk signaling pathway. It was observed that gut DCs express mRNA encoding for C-type lectin (CLEC) 7A, CLEC9A, CLEC12A, and CLEC4N. H. polygyrus bakeri infection downmodulated CLEC mRNA expression in these cells. Focusing on CLEC7A, which encodes for the dectin-1 receptor, flow analysis showed that H. polygyrus bakeri decreases dectin-1 expression on the intestinal DC subsets that drive Th1/Th17 development. DCs become unresponsive to the dectin-1 agonist curdlan and fail to phosphorylate Syk after agonist stimulation. Soluble worm products can block CLEC7A and Syk mRNA expression in gut DCs from uninfected mice after a brief in vitro exposure. Thus, downmodulation of Syk expression and phosphorylation in intestinal DCs could be important mechanisms through which helminths induce regulatory DCs that limit colitis.

Tuft cells, taste-chemosensory cells, orchestrate parasite type 2 immunity in the gut

The intestinal epithelium forms an essential barrier between a host and its microbiota. Protozoa and helminths are members of the gut microbiota of mammals, including humans, yet the many ways that gut epithelial cells orchestrate responses to these eukaryotes remain unclear. Here we show that tuft cells, which are taste-chemosensory epithelial cells, accumulate during parasite colonization and infection. Disruption of chemosensory signaling through the loss of TRMP5 abrogates the expansion of tuft cells, goblet cells, eosinophils, and type 2 innate lymphoid cells during parasite colonization. Tuft cells are the primary source of the parasite-induced cytokine interleukin-25, which indirectly induces tuft cell expansion by promoting interleukin-13 production by innate lymphoid cells. Our results identify intestinal tuft cells as critical sentinels in the gut epithelium that promote type 2 immunity in response to intestinal parasites.

Heligmosomoides polygyrus bakeri infection activates colonic Foxp3+ T cells enhancing their capacity to prevent colitis

Helminthic infections protect mice from colitis in murine models of inflammatory bowel disease and also may protect people. Helminths like Heligmosomoides polygyrus bakeri can induce regulatory T cells (Treg). Experiments explored whether H. polygyrus bakeri infection could protect mice from colitis through activation of colonic Treg and examined mechanisms of action. We showed that H. polygyrus bakeri infection increased the number of T cells expressing Foxp3 in the colon. More importantly, Foxp3(+)/IL-10(-) and Foxp3(+)/IL-10(+) T cell subsets isolated from the colon of H. polygyrus bakeri-infected mice prevented colitis when adoptively transferred into a murine model of inflammatory bowel disease, whereas Treg from uninfected mice could not provide protection. Only the transferred colonic Foxp3(+)/IL-10(-) T cells from H. polygyrus bakeri-infected mice readily accumulated in the colon and mesenteric lymph nodes of recipient mice, and they reconstituted the Foxp3(+)/IL-10(-) and Foxp3(+)/IL-10(+) T cell subsets. However, transferred Foxp3(+)/IL-10(+) T cells disappeared. IL-10 expression by Foxp3(+) T cells was necessary for colitis prevention. Thus, H. polygyrus bakeri infection activates colonic Foxp3(+) T cells, making them highly regulatory. The Foxp3(+) T cells that fail to express IL-10 may be critical for populating the colon with the Foxp3(+)/IL-10(+) T cells, which are required to control colitis.

Heligmosomoides polygyrus bakeri induces tolerogenic dendritic cells that block colitis and prevent antigen-specific gut T cell responses

Immunological diseases such as inflammatory bowel disease (IBD) are infrequent in less developed countries, possibly because helminths provide protection by modulating host immunity. In IBD murine models, the helminth Heligmosomoides polygyrus bakeri prevents colitis. It was determined whether H. polygyrus bakeri mediated IBD protection by altering dendritic cell (DC) function. We used a Rag IBD model where animals were reconstituted with IL10⁻/⁻ T cells, making them susceptible to IBD and with OVA Ag-responsive OT2 T cells, allowing study of a gut antigenic response. Intestinal DC from H. polygyrus bakeri-infected Rag mice added to lamina propria mononuclear cells (LPMC) isolated from colitic animals blocked OVA IFN-γ/IL-17 responses in vitro through direct contact with the inflammatory LPMC. DC from uninfected Rag mice displayed no regulatory activity. Transfer of DC from H. polygyrus bakeri-infected mice into Rag mice reconstituted with IL10⁻/⁻ T cells protected animals from IBD, and LPMC from these mice lost OVA responsiveness. After DC transfer, OT2 T cells populated the intestines normally. However, the OT2 T cells were rendered Ag nonresponsive through regulatory action of LPMC non-T cells. The process of regulation appeared to be regulatory T cell independent. Thus, H. polygyrus bakeri modulates intestinal DC function, rendering them tolerogenic. This appears to be an important mechanism through which H. polygyrus bakeri suppresses colitis. IFN-γ and IL-17 are colitogenic. The capacity of these DC to block a gut Ag-specific IFN-γ/IL-17 T cell response also is significant.

Alteration of the murine gut microbiota during infection with the parasitic helminth Heligmosomoides polygyrus

BACKGROUND

In a murine model of inflammatory bowel disease (IBD), treatment of colitis in IL-10 gene-deficient mice with the parasitic helminth Heligmosomoides polygyrus ameliorates colonic inflammation. The cellular and molecular mechanisms driving this therapeutic host response are being studied vigorously. One proposed mechanism is that H. polygyrus infection favors the outgrowth or suppression of certain bacteria, which in turn help modulate host immunity.

METHODS

To quantify the effect of H. polygyrus infection on the composition of the gastrointestinal (GI) tract microbiota, we conducted two independent microbial ecology analyses of C57BL/6 mice. We obtained and analyzed 3,353 bacterial 16S rRNA encoding gene sequences from the ileum and cecum of infected and uninfected mice as well as incective H. polygyrus larvae at the outset of the second experiment and adult worms taken directly from the mouse duodenum at the end of the second experiment.

RESULTS

We found that a significant shift in the abundance and relative distribution of bacterial species in the ileum of mice is associated with H. polygyrus infection. Members of the bacterial family Lactobacillaceae significantly increased in abundance in the ileum of infected mice reproducibly in two independent experiments despite having different microbiotas present at the outset of each experiment.

CONCLUSIONS

These data support the concept that helminth infection shifts the composition of intestinal bacteria. The clinical consequences of these shifts in intestinal flora are yet to be explored.

Heligmosomoides polygyrus infection can inhibit colitis through direct interaction with innate immunity

Less developed countries have a low incidence of immunological diseases like inflammatory bowel disease (IBD), perhaps prevented by the high prevalence of helminth infections in their populations. In the Rag IL-10(-/-) T cell transfer model of colitis, Heligmosomoides polygyrus, an intestinal helminth, prevents and reverses intestinal inflammation. This model of colitis was used to explore the importance of innate immunity in H. polygyrus protection from IBD. Rag mice briefly exposed to H. polygyrus before reconstitution with IL-10(-/-) colitogenic T cells are protected from colitis. Exposure to H. polygyrus before introduction of IL-10(-/-) and OT2 T cells reduced the capacity of the intestinal mucosa to make IFN-gamma and IL-17 after either anti-CD3 mAb or OVA stimulation. This depressed cytokine response was evident even in the absence of colitis, suggesting that the downmodulation in proinflammatory cytokine secretion was not just secondary to improvement in intestinal inflammation. Following H. polygyrus infection, dendritic cells (DCs) from the lamina propria of Rag mice displayed decreased expression of CD80 and CD86, and heightened expression of plasmacytoid dendritic cell Ag-1 and CD40. They were also less responsive to lamina proprias, producing less IL-12p40 and IL-10. Also diminished was their capacity to present OVA to OT2 T cells. These experiments infer that H. polygyrus does not require direct interactions with T or B cells to render animals resistant to colitis. DCs have an important role in driving both murine and human IBD. Data suggest that phenotypic alternations in mucosal DC function are part of the regulatory process.

Colonization with Heligmosomoides polygyrus suppresses mucosal IL-17 production

Helminth exposure appears to protect hosts from inappropriate inflammatory responses, such as those causing inflammatory bowel disease. A recently identified, strongly proinflammatory limb of the immune response is characterized by T cell IL-17 production. Many autoimmune type inflammatory diseases are associated with IL-17 release. Because helminths protect from these diseases, we examined IL-17 production in helminth-colonized mice. We colonized mice with Heligmosomoides polygyrus, an intestinal helminth, and analyzed IL-17 production by lamina propria mononuclear cells (LPMC) and mesenteric lymph node (MLN) cells. Colonization with H. polygyrus reduces IL-17A mRNA by MLN cells and inhibits IL-17 production by cultured LPMC and MLN cells. Helminth exposure augments IL-4 and IL-10 production. Blocking both IL-4 and IL-10, but not IL-10 alone, restores IL-17 production in vitro. Colonization of colitic IL-10-deficient mice with H. polygyrus suppresses LPMC IL-17 production and improves colitis. Ab-mediated blockade of IL-17 improves colitis in IL-10-deficient mice. Thus, helminth-associated inhibition of IL-17 production is most likely an important mechanism mediating protection from inappropriate intestinal inflammation.

Heligmosomoides polygyrus promotes regulatory T-cell cytokine production in the murine normal distal intestine

Helminths down-regulate inflammation and may prevent development of several autoimmune illnesses, such as inflammatory bowel disease. We determined if exposure to the duodenal helminth Heligmosomoides polygyrus establishes cytokine pathways in the distal intestine that may protect from intestinal inflammation. Mice received 200 H. polygyrus larvae and were studied 2 weeks later. Lamina propria mononuclear cells (LPMC) were isolated from the terminal ileum for analysis and in vitro experiments. Mice with H. polygyrus were resistant to trinitrobenzenesulfonic acid (TNBS)-induced colitis, a Th1 cytokine-dependent inflammation. Heligmosomoides polygyrus did not change the normal microscopic appearance of the terminal ileum and colon and minimally affected LPMC composition. However, colonization altered LPMC cytokine profiles, blocking gamma interferon (IFN-gamma) and interleukin 12 (IL-12) p40 release but promoting IL-4, IL-5, IL-13, and IL-10 secretion. IL-10 blockade in vitro with anti-IL-10 receptor (IL-10R) monoclonal antibody restored LPMC IFN-gamma and IL-12 p40 secretion. IL-10 blockade in vivo worsened TNBS colitis in H. polygyrus-colonized mice. Lamina propria CD4(+) T cells isolated from colonized mice inhibited IFN-gamma production by splenic T cells from worm-free mice. This inhibition did not require cell contact and was dependent on IL-10. Heligmosomoides polygyrus colonization inhibits Th1 and promotes Th2 and regulatory cytokine production in distant intestinal regions without changing histology or LPMC composition. IL-10 is particularly important for limiting the Th1 response. The T-cell origin of these cytokines demonstrates mucosal regulatory T-cell induction.

Induction of CD8+ regulatory T cells in the intestine by Heligmosomoides polygyrus infection

This study determined whether Heligmosomoides polygyrus induces intestinal regulatory T cells. Splenic T cells proliferate strongly when cultured with anti-CD3 and antigen-presenting cells (APC). Lamina propria T cells from mice with H. polygyrus mixed with normal splenic T cells from uninfected mice inhibited proliferation over 90%. Lamina propria T cells from mice without H. polygyrus only modestly affected T cell proliferation. The worm-induced regulatory T cell was CD8+ and required splenic T cell contact to inhibit proliferation. The regulation also was IL-10 independent, but TAP-dependent, suggesting that it requires major histocompatibility complex (MHC) class I interaction. Additional studies employed mice with transgenic T cells that did not express functional TGF-beta receptors. The lamina propria T regulator inhibited proliferation of these transgenic T cells nearly 100%, suggesting that TGF-beta signaling via the T cell was not required. CD8+ T cells were needed for worms to reverse piroxicam-induced colitis in Rag mice (T and B cell deficient) reconstituted with IL-10-/- T cells. Thus H. polygyrus induces a regulatory CD8+ lamina propria T cell that inhibits T cell proliferation and that appears to have a role in control of colitis.

CD4+ T cells from IL-10-deficient mice transfer susceptibility to NSAID-induced Rag colitis

Products of arachidonic acid metabolism are important for mucosal homeostasis, because blockade of this pathway with an NSAID triggers rapid onset of severe colitis in the IL-10 knockout (IL-10(-/-)) model of IBD. Rag mice do not make T or B cells. This study determined whether reconstitution of Rag mice with T cells from IL-10(-/-) mice transferred NSAID colitis susceptibility. Rag mice were reconstituted by intraperitoneal injection with splenocytes from wild-type (WT) or IL-10(-/-) animals. Colitis was induced by using piroxicam and was graded histologically. Isolated lamina propria mononuclear cells (LPMC), lamina propria T cells, and LPMC depleted of T cells from reconstituted Rag mice were studied for cytokine production. Only animals reconstituted with IL-10(-/-) CD4(+) T cells and administered piroxicam developed severe colitis. LPMC from these colitic animals made IFN-gamma, whose production was dependent on T cells. Some IL-10 was produced but only from non-T cells. LPMC from the healthy Rag mice that were reconstituted with WT T cells and were piroxicam resistant made much more IL-10. This was mostly T cell dependent. In conclusion, only CD4(+) T cells from IL-10(-/-) animals leave Rag mice susceptible to NSAID-induced, Th1 colitis. Lamina propria T cells normally make large quantities of IL-10, suggesting that IL-10 from T cells may be protective.

Cutting Edge: Hemokinin Has Substance P-Like Function and Expression in Inflammation

Substance P (SP) belongs to the tachykinin family of molecules. SP, cleaved from preprotachykinin A, is a neuropeptide and a proinflammatory leukocyte product. SP engages neurokinin 1 receptor (NK-1R) to stimulate cells. Hemokinin (HK) is another tachykinin that binds NK-1R. HK comes from preprotachykinin C, which is distinct from preprotachykinin A. We determined whether HK functions like SP at inflammatory sites. Preprotachykinin C mRNA was in murine schistosome granulomas and intestinal lamina propria mononuclear cells. Granuloma T cells and macrophages expressed preprotachykinin C mRNA. HK bound granuloma T cell NK-1R with high affinity. SP and HK stimulated IFN-gamma production with equal potency. NK-1R antagonist blocked the effect of SP and HK on IFN-gamma secretion. Thus, both HK and SP are expressed at sites of chronic inflammation and share cell origin, receptor, and immunoregulatory function. Two distinct but functionally overlapping tachykinins govern inflammation through NK-1R at sites of chronic inflammation.

T cell substance P receptor governs antigen-elicited IFN-gamma production

Substance P (SP) enhances antigen-dependent T cell IFN-gamma production. It was determined if a T cell neurokinin-1 receptor (NK-1R) was critical for IFN-gamma regulation. T cells from schistosome-infected mice were mixed with splenocytes from uninfected NK-1R knockout (KO) animals. Thus only the schistosome egg antigen-specific T cells expressed NK-1R. The cells were cultured 18 h with or without SP. SP enhanced antigen-induced IFN-gamma production fourfold without affecting IL-4 or IL-5 secretion. NK-1R inhibitor blocked this stimulation. Neither purified T cells nor naive KO splenocytes cultured alone responded to antigen. To further define the importance of T cell NK-1R, we developed a T cell-selective NK-1R KO mouse by reconstituting T cell-deficient Rag mice with NK-1R KO T cells. These mice challanged with schistosomiasis developed abnormal liver granulomas. Granuloma size was smaller in T cell-selective NK-1R KO mice compared with granulomas in Rag reconstituted with normal T cells. Splenocytes and granuloma cells from NK-1R KO mice made less IFN-gamma. The mice also made less IgG2a. Thus T cell NK-1R is important for IFN-gamma regulation.

IL-4 inhibits vasoactive intestinal peptide production by macrophages

In schistosomiasis, eggs induce granulomas that have a vasoactive intestinal peptide (VIP) immunoregulatory circuit. This study explored the regulation of VIP production at sites of inflammation. Splenocytes from uninfected C57BL/6 mice expressed VIP mRNA and protein, which stopped following egg deposition. Eggs induce a Th2 response, suggesting that Th2 cytokines like interleukin (IL)-4 can regulate VIP. To address this issue, splenocytes from uninfected mice were incubated for 4 h with or without recombinant IL-4. IL-4 inhibited VIP mRNA expression. F4/80+ macrophages were the source of constitutively expressed VIP, subject to IL-4 regulation. In IL-4 knockout mice, splenic VIP production did not downmodulate during schistosome infection, suggesting that IL-4 is a critical cytokine regulating VIP production in wild-type mouse spleen. IL-4-producing granulomas in schistosomiasis made VIP. Experiments showed that granuloma VIP derived from F4/80- (nonmacrophage) cell populations, explaining this paradox. Granuloma F4/80+ cells from IL-4 knockout mice expressed VIP. Thus macrophages can make VIP, which is subject to IL-4 regulation. However, in the Th2 granulomas, other cell types produce VIP, which compensates for loss of macrophages as a source of this molecule.

TGF-beta and IL-10 regulation of IFN-gamma produced in Th2-type schistosome granulomas requires IL-12

Interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) regulate CD4+ T cell interferon-gamma (IFN-gamma) secretion in schistosome granulomas. The role of IL-12 was determined using C57BL/6 and CBA mice. C57BL/6 IL-4-/- granuloma cells were stimulated to produce IFN-gamma when cultured with IL-10 or TGF-beta neutralizing monoclonal antibody. In comparison, C57BL/6 wild-type (WT) control granuloma cells produced less IFN-gamma. IL-12, IL-18, and soluble egg antigen stimulated IFN-gamma release from C57BL/6 IL-4-/- and WT mice. IFN-gamma production in C57 IL-4-/- and WT granulomas was IL-12 dependent, because IL-12 blockade partly abrogated IFN-gamma secretion after stimulation. All granuloma cells released IL-12 (p70 and p40), and IL-12 production remained constant after anti-TGF-beta, anti-IL-10, recombinant IL-18, or antigen stimulation. C57 WT and IL-4-/- mouse granuloma cells expressed IL-12 receptor (IL-12R) beta1-subunit mRNA but little beta2 mRNA. TGF-beta or IL-10 blockade did not influence beta1 or beta2 mRNA expression. CBA mouse dispersed granuloma cells released no measurable IFN-gamma, produced IL-12 p70 and little p40, and expressed IL-12R beta2 and little beta1 mRNA. In T helper 2 (Th2) granulomas of C57BL/6 WT and IL-4-/- mice, cells produce IL-12 (for IFN-gamma production) and IL-10 and TGF-beta modulate IFN-gamma secretion via mechanisms independent of IL-12 and IL-12R mRNA regulation. We found substantial differences in control of granuloma IFN-gamma production and IL-12 circuitry in C57BL/6 and CBA mice.

Interleukin 12 and antigen independently induce substance P receptor expression in T cells in murine schistosomiasis mansoni

Substance P (SP) regulates interferon-gamma (IFN-gamma) production through interaction with the SP receptor NK1 (SPr) on T cells at sites of inflammation. Using murine schistosomiasis, we evaluated whether SPr expression was subject to immunoregulation. Splenocytes from schistosome-infected mice cultured for < or =18 h did not express SPr, as determined by quantitative polymerase chain reaction assay. However, exposure to schistosome egg antigen (SEA) for < or =4 h induced strong receptor expression. Experiments using splenocytes fractionated with antibody-coupled, paramagnetic beads showed that induction localized exclusively to T cells. Receptor protein expression was confirmed with Western blot. Interleukin 12 (IL-12) also induced strong T-cell SPr expression. Both SEA and IL-12 remained strong inducers of T-cell SPr in lymphocytes from the IL-12 (p40) and IFN-gamma R double-knockout mouse, which suggested that SEA did not require IL-12 to induce SPr and that both worked independently of IFN-gamma. Splenocytes from wild-type mice cultured with SEA and neutralizing anti-IL-12 monoclonal antibody (mAb) also showed SPr induction. However, anti-Ia mAb inhibited SEA induction of SPR: Thus, SPr is inducible on T cells. SEA induces SPr through interaction with T-cell receptor (TCR), independently of IL-12 and IFN-gamma. IL-12 induces SPr independently of TCR activation and IFN-gamma expression. SP and its receptor, which regulate IFN-gamma production, are probably part of the IL-12-Th1 circuit.

IL-4 regulates VIP receptor subtype 2 mRNA (VPAC2) expression in T cells in murine schistosomiasis

In murine schistosomiasis, granuloma T cells express VPAC2 mRNA, whereas there is none in splenocytes. This suggests that T cell VPAC2 mRNA is inducible. To address this issue, splenocytes from schistosome-infected mice were incubated with anti-CD3 to induce VPAC2 mRNA, which only appeared when cell cultures also contained anti-IL-4 mAb. Granuloma cells expressed VPAC2 mRNA. This natural expression decreased substantially when cells were cultured 3 days in vitro. However, granuloma cells cultured with anti-IL-4 mAb strongly expressed VPAC2 mRNA. IL-4 KO mice were examined to further address the importance of IL-4 in VPAC2 regulation. Splenocytes and dispersed granuloma cells from IL-4 KO animals had substantially more VPAC2 mRNA than those in wild-type controls. VPAC2 mRNA content decreased when cells were cultured with rIL-4. VPAC2 mRNA localized to CD4+ T cells. Th1 cell lines expressed VPAC2 mRNA much stronger than Th2 cells. Anti-IL-4 mAb increased VPAC2 mRNA expression in Th2 cells cultured in vitro. However, rIL-4 could not suppress VPAC2 mRNA expression in Th1 cells. Thus, VPAC2 is an inducible CD4+ T cell receptor, and IL-4 down-modulates VPAC2 mRNA expression in Th2 cells.

SSTR2A is the dominant somatostatin receptor subtype expressed by inflammatory cells, is widely expressed and directly regulates T cell IFN-gamma release

Macrophages secrete the immunoregulatory peptide somatostatin (SOM) that inhibits IFN-gamma release by splenocytes and granuloma cells of schistosome-infected mice. In this report we demonstrate that granuloma cells express mRNA for the SOM receptor SSTR2 but not the other four SSTR subtypes. Blocking SSTR2 activity with anti-SSTR2 antiserum prevents SOM inhibition of T cell IFN-gamma production. This demonstrates that SOM regulates T cell function via SSTR2. Two isoforms of SSTR2 exist due to alternative RNA splicing. We developed sensitive and specific competitive PCR assays to quantify total SSTR2, SSTR2A and SSTR2B mRNA levels. The SSTR2A isoform accounts for 99% of inflammatory cell SSTR2 mRNA and does not appear to be regulated at the transcripitonal level. B cells and macrophage cell lines also express SSTR2 mRNA which raises the possibility that SOM influences T cell IFN-gamma release by regulating accessory cell function. We show that SOM acts directly on T cells to inhibit TCR-stimulated IFN-gamma release. Thus, SOM may directly regulate T cell IFN-gamma release at inflammatory sites.

The Substance P Receptor Is Necessary for a Normal Granulomatous Response in Murine Schistosomiasis Mansoni

Immune cells within the granulomas of murine schistosomiasis mansoni make the neuropeptide substance P (SP) and express neurokine 1 receptor, which is the specific receptor for substance P (SPr). It was determined if mice with deletion of the SPr (SPr−/−) would develop a normal granulomatous response to schistosome ova during the course of natural infection. Mean liver granuloma size was smaller in SPr−/− mice compared with that of wild-type control animals. Although flow analysis revealed little difference in the cellular composition of the granulomas, both splenocytes and granuloma cells from SPr−/− mice produced much less IFN-γ and IgG2a and less IgE. The expression of Th2 cytokines (IL-4/IL-5) and IgG1 was comparable to the wild-type control. The mouse with targeted disruption of its SPr had the nonmammalian gene encoding the enzyme β-galactosidase inserted in exon 1 of the SPr gene. There was β-galactosidase activity in many mononuclear cells scattered throughout the schistosome granulomas of SPr−/− mice. Also, a granuloma T cell line derived from this transgenic mouse produced β-galactosidase. These results provide further evidence that in murine schistosomiasis SPr is displayed commonly on granuloma inflammatory cells and is important for granuloma development and expression of IFN-γ circuitry in this natural infection.

The substance P receptor is necessary for a normal granulomatous response in murine schistosomiasis mansoni

Immune cells within the granulomas of murine schistosomiasis mansoni make the neuropeptide substance P (SP) and express neurokine 1 receptor, which is the specific receptor for substance P (SPr). It was determined if mice with deletion of the SPr (SPr-/-) would develop a normal granulomatous response to schistosome ova during the course of natural infection. Mean liver granuloma size was smaller in SPr-/- mice compared with that of wild-type control animals. Although flow analysis revealed little difference in the cellular composition of the granulomas, both splenocytes and granuloma cells from SPr-/- mice produced much less IFN-gamma and IgG2a and less IgE. The expression of Th2 cytokines (IL-4/IL-5) and IgG1 was comparable to the wild-type control. The mouse with targeted disruption of its SPr had the nonmammalian gene encoding the enzyme beta-galactosidase inserted in exon 1 of the SPr gene. There was beta-galactosidase activity in many mononuclear cells scattered throughout the schistosome granulomas of SPr-/- mice. Also, a granuloma T cell line derived from this transgenic mouse produced beta-galactosidase. These results provide further evidence that in murine schistosomiasis SPr is displayed commonly on granuloma inflammatory cells and is important for granuloma development and expression of IFN-gamma circuitry in this natural infection.

Substance P Regulates Somatostatin Expression in Inflammation

Substance P (SP) and somatostatin (SOM) are made at mucosal surfaces and sites of inflammation. There is a SP/SOM immunoregulatory circuit that modulates the IFN-γ response in murine schistosomiasis. SP enhances, while SOM decreases, IFN-γ secretion. Various inflammatory mediators induce macrophages to make SOM, but no known factor limits this expression. It was discovered that SP regulates SOM synthesis. Splenocytes from normal, uninfected mice cultured with LPS, IFN-γ, or IL-10 for 4 h strongly expressed SOM mRNA, but failed to do so in the presence of SP. The inhibition with 10−9 M SP was &gt;85% shown by quantitative PCR. Also, splenocyte SOM content decreased from 1048 ± 275 to &lt;10 pg/4 × 108 cells following SP exposure. Immunohistochemistry identified SOM solely within splenic macrophages following cytokine stimulation. Mice infected with Schistosoma mansoni form granulomas in the liver and intestines resulting from deposition of parasite eggs in these organs. The granulomas contain macrophages that make SOM constitutively. SP at 10−8 M decreased SOM mRNA expression &gt;90% in dispersed granuloma cells cultured for 4 h or longer. Specific SP receptor antagonists blocked SP suppression of SOM expression in splenocytes and dispersed granuloma cells, showing that an authentic SP receptor mediated the regulation. Additional studies revealed that IL-4 antagonized the SP effect in the spleen. It is concluded that in granulomas and splenocytes from mice with schistosomiasis and in splenocytes from uninfected animals that 1) SP inhibits macrophage SOM induction and ongoing expression at the mRNA and protein levels acting through the SP receptor, and 2) IL-4 can antagonizes this SP effect.

Substance P regulates somatostatin expression in inflammation

Substance P (SP) and somatostatin (SOM) are made at mucosal surfaces and sites of inflammation. There is a SP/SOM immunoregulatory circuit that modulates the IFN-gamma response in murine schistosomiasis. SP enhances, while SOM decreases, IFN-gamma secretion. Various inflammatory mediators induce macrophages to make SOM, but no known factor limits this expression. It was discovered that SP regulates SOM synthesis. Splenocytes from normal, uninfected mice cultured with LPS, IFN-gamma, or IL-10 for 4 h strongly expressed SOM mRNA, but failed to do so in the presence of SP. The inhibition with 10(-9) M SP was > 85% shown by quantitative PCR. Also, splenocyte SOM content decreased from 1048 +/- 275 to < 10 pg/4 x 10(8) cells following SP exposure. Immunohistochemistry identified SOM solely within splenic macrophages following cytokine stimulation. Mice infected with Schistosoma mansoni form granulomas in the liver and intestines resulting from deposition of parasite eggs in these organs. The granulomas contain macrophages that make SOM constitutively. SP at 10(-8) M decreased SOM mRNA expression > 90% in dispersed granuloma cells cultured for 4 h or longer. Specific SP receptor antagonists blocked SP suppression of SOM expression in splenocytes and dispersed granuloma cells, showing that an authentic SP receptor mediated the regulation. Additional studies revealed that IL-4 antagonized the SP effect in the spleen. It is concluded that in granulomas and splenocytes from mice with schistosomiasis and in splenocytes from uninfected animals that 1) SP inhibits macrophage SOM induction and ongoing expression at the mRNA and protein levels acting through the SP receptor, and 2) IL-4 can antagonizes this SP effect.

IL-6-deficient mice form granulomas in murine schistosomiasis that exhibit an altered B cell response

IL-6 can play an important role in various biological activities. Using IL-6-deficient, 129 x C57BL/6 mice and normal littermate controls, we studied the role of IL-6 in granulomas of mice infected with schistosomiasis mansoni. Granulomas from IL-6(+/+) mice produced large quantities of IL-6, derived from T, B, and myeloid cells. Yet, IL-6 mutant mice generated normal-appearing granulomas of appropriate size. Multiple-parameter flow cytometric analysis of dispersed granuloma cells revealed no substantial differences. Granuloma cells and splenocytes were cultured in vitro to measure cytokine and immunoglobulin production. Compared to control cells, IL-6(-/-) granuloma cells secreted more IL-4, IL-5, and IL-10. However, splenocytes secreted cytokines comparably. In the IL-6(-/-) state, the granuloma cells released less IgE and substantially more IgM, although IgG1, IgG2a, and IgA secretion remained normal. ELISPOT assay showed that dispersed granuloma cells from IL-6-deficient animals had substantially more IgM-secreting B cells. Thus, schistosome granulomas make IL-6 that is not essential for most aspects of granuloma development. However, IL-6 deficiency results in some disturbance of granuloma cytokine and immunoglobulin expression.

Localization and regulation of IFN-gamma production within the granulomas of murine schistosomiasis in IL-4-deficient and control mice

Schistosome granulomas from normal or IL-4-deficient C57BL/6 mice make little IFN-gamma and show no Th1 polarization. This could signify that these granulomas have few cells capable of IFN-gamma synthesis or that such cells are under tight control. Granulomas can make IL-10 and TGF-beta, which can regulate IFN-gamma synthesis. Using FACS analysis and ELISA, we explored the origin and regulation of IFN-gamma in schistosome granulomas from both IL-4(-/-) and IL-4(+/+) mice. FACS analysis of intracytoplasmic IFN-gamma staining showed that some granuloma Thy1.2+ T cells (CD8+ and CD4+) express IFN-gamma. Granulomas had NK1.1+ cells, but they appeared to produce little or no IFN-gamma. Purified granuloma Thy1.2+ cells made IFN-gamma in vitro, whereas isolated NK1.1+ lymphocytes secreted little even with rIL-12 stimulation. Culture of granuloma cells with blocking anti-IL-10 or anti-TGF-beta mAb or with rIL-12 substantially increased T cell IFN-gamma synthesis, particularly in the IL-4(-/-) animals. Cultured granuloma cells depleted of Thy1.2+ lymphocytes by Ab and C released no IFN-gamma. It is concluded that granuloma IFN-gamma comes from T cells, not NK cells. Also, this T cell-derived IFN-gamma is subject to IL-10 and TGF-beta regulation, which is particularly evident in IL-4(-/-) mice. Thus, the Th2 granuloma of schistosomiasis has large numbers of activated Th1 or Th0 lymphocytes that are under tight restraint.

Localization and Regulation of IFN-γ Production Within the Granulomas of Murine Schistosomiasis in IL-4-Deficient and Control Mice

Schistosome granulomas from normal or IL-4-deficient C57BL/6 mice make little IFN-γ and show no Th1 polarization. This could signify that these granulomas have few cells capable of IFN-γ synthesis or that such cells are under tight control. Granulomas can make IL-10 and TGF-β, which can regulate IFN-γ synthesis. Using FACS analysis and ELISA, we explored the origin and regulation of IFN-γ in schistosome granulomas from both IL-4−/− and IL-4+/+ mice. FACS analysis of intracytoplasmic IFN-γ staining showed that some granuloma Thy1.2+ T cells (CD8+ and CD4+) express IFN-γ. Granulomas had NK1.1+ cells, but they appeared to produce little or no IFN-γ. Purified granuloma Thy1.2+ cells made IFN-γ in vitro, whereas isolated NK1.1+ lymphocytes secreted little even with rIL-12 stimulation. Culture of granuloma cells with blocking anti-IL-10 or anti-TGF-β mAb or with rIL-12 substantially increased T cell IFN-γ synthesis, particularly in the IL-4−/− animals. Cultured granuloma cells depleted of Thy1.2+ lymphocytes by Ab and C released no IFN-γ. It is concluded that granuloma IFN-γ comes from T cells, not NK cells. Also, this T cell-derived IFN-γ is subject to IL-10 and TGF-β regulation, which is particularly evident in IL-4−/− mice. Thus, the Th2 granuloma of schistosomiasis has large numbers of activated Th1 or Th0 lymphocytes that are under tight restraint.

Preprosomatostatin Messenger RNA Is Expressed by Inflammatory Cells and Induced by Inflammatory Mediators and Cytokines

Somatostatin (SOM) is a 14-amino acid cyclic peptide that regulates granulomatous inflammation. SOM inhibits the release of IFN-γ from murine granuloma T cells that express SOM receptors. SOM is synthesized as preprosomatostatin (ppSOM), a precursor peptide that is cleaved to release active SOM. In this paper, we demonstrate that granuloma cells express mRNA for this important immunoregulator, and that inflammatory mediators rapidly induce ppSOM mRNA in the splenocytes of uninfected, normal (NL) mice. We developed a sensitive, quantitative PCR assay that measures ppSOM mRNA down to 100 transcripts per μg of total RNA. Dispersed granuloma cells expressed authentic ppSOM mRNA as determined by RT-PCR and cDNA sequencing. The PCR assay readily detected ppSOM mRNA in splenocytes isolated from schistosome-infected mice, but not in splenocytes from NL mice. Splenic ppSOM mRNA expression correlated with the onset of parasite egg deposition and granuloma formation. A 4-h in vitro stimulation with LPS, rIL-10, rIFN-γ, rTNF-α, prostaglandin E2, or dibutyryl cAMP induced ppSOM mRNA in NL splenocytes that otherwise lacked this transcript. Splenocytes from severe combined immunodeficient or recombination activating gene 1-deficient mice expressed ppSOM after exposure to rIL-10, suggesting that neither T nor B cells are necessary for ppSOM mRNA induction. A survey of cell lines demonstrated expression of ppSOM mRNA by P388D1 and J774A.1 macrophage-like cells. These data suggest that SOM, which is probably derived from macrophages, is an inducible component of the innate immune system that regulates T cell IFN-γ production.

Preprosomatostatin messenger RNA is expressed by inflammatory cells and induced by inflammatory mediators and cytokines

Somatostatin (SOM) is a 14-amino acid cyclic peptide that regulates granulomatous inflammation. SOM inhibits the release of IFN-gamma from murine granuloma T cells that express SOM receptors. SOM is synthesized as preprosomatostatin (ppSOM), a precursor peptide that is cleaved to release active SOM. In this paper, we demonstrate that granuloma cells express mRNA for this important immunoregulator, and that inflammatory mediators rapidly induce ppSOM mRNA in the splenocytes of uninfected, normal (NL) mice. We developed a sensitive, quantitative PCR assay that measures ppSOM mRNA down to 100 transcripts per microg of total RNA. Dispersed granuloma cells expressed authentic ppSOM mRNA as determined by RT-PCR and cDNA sequencing. The PCR assay readily detected ppSOM mRNA in splenocytes isolated from schistosome-infected mice, but not in splenocytes from NL mice. Splenic ppSOM mRNA expression correlated with the onset of parasite egg deposition and granuloma formation. A 4-h in vitro stimulation with LPS, rIL-10, rIFN-gamma, rTNF-alpha, prostaglandin E2, or dibutyryl cAMP induced ppSOM mRNA in NL splenocytes that otherwise lacked this transcript. Splenocytes from severe combined immunodeficient or recombination activating gene 1-deficient mice expressed ppSOM after exposure to rIL-10, suggesting that neither T nor B cells are necessary for ppSOM mRNA induction. A survey of cell lines demonstrated expression of ppSOM mRNA by P388D1 and J774A.1 macrophage-like cells. These data suggest that SOM, which is probably derived from macrophages, is an inducible component of the innate immune system that regulates T cell IFN-gamma production.

The granulomatous response in murine Schistosomiasis mansoni does not switch to Th1 in IL-4-deficient C57BL/6 mice

IL-4 plays an important role in polarizing inflammation toward a Th2 response. It remains uncertain, however, whether IL-4 also serves to prevent expression of Th1 inflammation. Therefore, using a genetically pure C57BL/6 IL-4-deficient mouse, we studied the role of IL-4 in regulating the production of IFN-gamma and Th1 inflammation in the granulomas of mice infected with Schistosoma mansoni. In contrast to normal animals, IL-4 mutant mice generated smaller liver granulomas that contained fewer eosinophils and no mast cells. Collagenase-dispersed granuloma cells were analyzed by flow cytometry and cultured in vitro to measure cytokine and Ig production. Compared with control granuloma cells, IL-4-/- cells secreted only small quantities of IL-5 and IL-10. Also, there was impaired expression of the IL-4-dependent molecules IgE and IgG1 as well as B cell surface class II and CD23. Yet the granulomas of IL-4 -/- animals produced little IFN-gamma, IgG2a, or other molecules associated with Th1 inflammation even after Ag or anti-CD3 stimulation. Splenocytes from IL-4 -/- animals stimulated with schistosome Ag also failed to produce a Th1 response. Our data show that most aspects of the Th2 response in murine schistosomiasis are highly dependent on IL-4 production. But in the absence of IL-4, neither the natural local granulomatous response to schistosome ova nor the systemic response to soluble egg Ag switches to the type 1 phenotype. Thus the production of IL-4 early in the inflammatory response is not the only factor preventing Th1 expression in inflammation.

The granulomatous response in murine Schistosomiasis mansoni does not switch to Th1 in IL-4-deficient C57BL/6 mice

IL-4 plays an important role in polarizing inflammation toward a Th2 response. It remains uncertain, however, whether IL-4 also serves to prevent expression of Th1 inflammation. Therefore, using a genetically pure C57BL/6 IL-4-deficient mouse, we studied the role of IL-4 in regulating the production of IFN-gamma and Th1 inflammation in the granulomas of mice infected with Schistosoma mansoni. In contrast to normal animals, IL-4 mutant mice generated smaller liver granulomas that contained fewer eosinophils and no mast cells. Collagenase-dispersed granuloma cells were analyzed by flow cytometry and cultured in vitro to measure cytokine and Ig production. Compared with control granuloma cells, IL-4-/- cells secreted only small quantities of IL-5 and IL-10. Also, there was impaired expression of the IL-4-dependent molecules IgE and IgG1 as well as B cell surface class II and CD23. Yet the granulomas of IL-4 -/- animals produced little IFN-gamma, IgG2a, or other molecules associated with Th1 inflammation even after Ag or anti-CD3 stimulation. Splenocytes from IL-4 -/- animals stimulated with schistosome Ag also failed to produce a Th1 response. Our data show that most aspects of the Th2 response in murine schistosomiasis are highly dependent on IL-4 production. But in the absence of IL-4, neither the natural local granulomatous response to schistosome ova nor the systemic response to soluble egg Ag switches to the type 1 phenotype. Thus the production of IL-4 early in the inflammatory response is not the only factor preventing Th1 expression in inflammation.

T cell vasoactive intestinal peptide receptor subtype expression differs between granulomas and spleen of schistosome-infected mice

Granulomas form in the liver and intestines of mice infected with the parasite Schistosoma mansoni. Vasoactive intestinal peptide (VIP) is a neurokine that can modulate aspects of the immune response by acting through receptors within the granuloma. Cloned are two novel VIP receptor (VIPR) mRNAs (VIPR1 and VIPR2) that also bind a second neurokine called pituitary adenylated cyclase-activating polypeptide (PACAP). The objective of this study was to determine if granulomas express either VIPR1 or VIPR2. Using a radioligand-binding assay, it was established that PACAP is as effective as VIP at displacing radiolabeled VIP from splenocytes and granuloma cells, and that most if not all VIPRs in the spleen and granulomas bind PACAP. PCR amplification of reverse transcribed RNA determined that granulomas express both VIPR1 and VIPR2 mRNAs. Gel electrophoresis and nucleotide sequencing confirmed the authenticity of the PCR products. Also, both receptor subtypes were amplified from several granuloma CD4+ T cell lines; yet reverse transcribed RNA from T cell-depleted, dispersed granuloma cells had only VIPR1 RNA. It is notable that reverse transcriptase-PCR detected only VIPR1 in the thymus and spleen, which are organs rich in T lymphocytes. Thus, the granulomas and spleens from mice with schistosomiasis contain cells that display authentic VIP/PACAP receptors. Moreover, these data suggest that T cells in different compartments vary in VIPR subtype expression. VIPR1 and VIPR2 may have different physiologic roles in inflammation.

T cell vasoactive intestinal peptide receptor subtype expression differs between granulomas and spleen of schistosome-infected mice

Granulomas form in the liver and intestines of mice infected with the parasite Schistosoma mansoni. Vasoactive intestinal peptide (VIP) is a neurokine that can modulate aspects of the immune response by acting through receptors within the granuloma. Cloned are two novel VIP receptor (VIPR) mRNAs (VIPR1 and VIPR2) that also bind a second neurokine called pituitary adenylated cyclase-activating polypeptide (PACAP). The objective of this study was to determine if granulomas express either VIPR1 or VIPR2. Using a radioligand-binding assay, it was established that PACAP is as effective as VIP at displacing radiolabeled VIP from splenocytes and granuloma cells, and that most if not all VIPRs in the spleen and granulomas bind PACAP. PCR amplification of reverse transcribed RNA determined that granulomas express both VIPR1 and VIPR2 mRNAs. Gel electrophoresis and nucleotide sequencing confirmed the authenticity of the PCR products. Also, both receptor subtypes were amplified from several granuloma CD4+ T cell lines; yet reverse transcribed RNA from T cell-depleted, dispersed granuloma cells had only VIPR1 RNA. It is notable that reverse transcriptase-PCR detected only VIPR1 in the thymus and spleen, which are organs rich in T lymphocytes. Thus, the granulomas and spleens from mice with schistosomiasis contain cells that display authentic VIP/PACAP receptors. Moreover, these data suggest that T cells in different compartments vary in VIPR subtype expression. VIPR1 and VIPR2 may have different physiologic roles in inflammation.

Local suppression of IFN-gamma in hepatic granulomas correlates with tissue-specific replication of Leishmania chagasi

BALB/c mice are susceptible to infection with the visceralizing species of Leishmania, Leishmania chagasi. The parasite load initially rises in the liver and spontaneously subsides, whereas parasite multiplication begins later and remains lower in the spleen. To investigate whether this organ-specific multiplication of L. chagasi correlates with localized immune responses, we compared cytokine production by splenic vs hepatic immune cells. Livers from infected mice contained granulomas harboring intracellular L. chagasi amastigotes, whereas few amastigotes were present in the spleen. FACS analysis granuloma cells showed granuloma lymphocytes expressed a memory/effector phenotype. Granuloma cells cultured in vitro produced IL-10 and IL-6 but no detectable IFN-gamma, IL-4 or IL-5. In contrast, splenocytes from the same animals secreted IFN-gamma, IL-4, IL-6, and IL-10. T cells were depleted from granuloma cells by immune lysis, and the results indicated that IL-10 and IL-6 were derived at least in part from a non-T cell compartment. Paradoxically, FACS-purified Thy-1+ granuloma lymphocytes were able to produce IFN-gamma in the absence of other granuloma cells, suggesting IFN-gamma production might usually be inhibited by a granuloma-associated non-T cell element. Coculture of splenocytes with either granuloma cells or supernatants from granuloma cultures inhibited the usual splenocyte production of IFN-gamma and IL-4 but not IL-10. Thus, there may be a unique granuloma-associated suppressive factor accounting for the absence of IFN-gamma in hepatic granuloma cultures. It may be the absence of IFN-gamma in the liver and presence in the spleen that allows or inhibits parasite survival, respectively, in these different locations.

Local suppression of IFN-gamma in hepatic granulomas correlates with tissue-specific replication of Leishmania chagasi

BALB/c mice are susceptible to infection with the visceralizing species of Leishmania, Leishmania chagasi. The parasite load initially rises in the liver and spontaneously subsides, whereas parasite multiplication begins later and remains lower in the spleen. To investigate whether this organ-specific multiplication of L. chagasi correlates with localized immune responses, we compared cytokine production by splenic vs hepatic immune cells. Livers from infected mice contained granulomas harboring intracellular L. chagasi amastigotes, whereas few amastigotes were present in the spleen. FACS analysis granuloma cells showed granuloma lymphocytes expressed a memory/effector phenotype. Granuloma cells cultured in vitro produced IL-10 and IL-6 but no detectable IFN-gamma, IL-4 or IL-5. In contrast, splenocytes from the same animals secreted IFN-gamma, IL-4, IL-6, and IL-10. T cells were depleted from granuloma cells by immune lysis, and the results indicated that IL-10 and IL-6 were derived at least in part from a non-T cell compartment. Paradoxically, FACS-purified Thy-1+ granuloma lymphocytes were able to produce IFN-gamma in the absence of other granuloma cells, suggesting IFN-gamma production might usually be inhibited by a granuloma-associated non-T cell element. Coculture of splenocytes with either granuloma cells or supernatants from granuloma cultures inhibited the usual splenocyte production of IFN-gamma and IL-4 but not IL-10. Thus, there may be a unique granuloma-associated suppressive factor accounting for the absence of IFN-gamma in hepatic granuloma cultures. It may be the absence of IFN-gamma in the liver and presence in the spleen that allows or inhibits parasite survival, respectively, in these different locations.

T lymphocytes isolated from the hepatic granulomas of schistosome-infected mice express somatostatin receptor subtype II (SSTR2) messenger RNA

Schistosomiasis mansoni is a disease characterized by liver and intestinal granulomas. Previous investigations in our laboratory showed that nylon wool-adherent CD4+ T lymphocytes isolated from murine hepatic schistosome granulomas express receptors for somatostatin 1-14. Moreover, somatostatin 1-14 substantially decreased IFN-gamma and IgG2a, but not IL-5 secretion by dispersed granuloma cells. This paper extends these observations by defining the somatostatin receptor (SSTR) isoform most likely expressed by granuloma inflammatory lymphocytes. Amplification of mRNA by reverse transcription PCR shows SSTR1, SSTR2, and SSTR3 mRNA in normal mouse brain and other tissues. Nevertheless, only the SSTR2 PCR product was amplified from granuloma cell RNA. The nucleotide sequence of the granuloma SSTR2 PCR product from inflammatory cells is identical to the CBA murine brain SSTR2 cDNA sequence. Granuloma-derived T cell lines, FACS-isolated granuloma CD4+ T cells, thymocytes, splenocytes, and cloned T cell lines all contain mRNA for SSTR2 by reverse transcription PCR. Moreover, both SSTR2A and the splice variant SSTR2B can be amplified from dispersed granuloma cells, granuloma T cell lines, thymocytes, and splenocytes. This is the first demonstration that inflammatory cells produce mRNA for an authentic somatostatin receptor. It is probable that the lymphocyte SSTR2 receptor mediates somatostatin-induced modulation of IFN-gamma secretion.

T lymphocytes isolated from the hepatic granulomas of schistosome-infected mice express somatostatin receptor subtype II (SSTR2) messenger RNA

Schistosomiasis mansoni is a disease characterized by liver and intestinal granulomas. Previous investigations in our laboratory showed that nylon wool-adherent CD4+ T lymphocytes isolated from murine hepatic schistosome granulomas express receptors for somatostatin 1-14. Moreover, somatostatin 1-14 substantially decreased IFN-gamma and IgG2a, but not IL-5 secretion by dispersed granuloma cells. This paper extends these observations by defining the somatostatin receptor (SSTR) isoform most likely expressed by granuloma inflammatory lymphocytes. Amplification of mRNA by reverse transcription PCR shows SSTR1, SSTR2, and SSTR3 mRNA in normal mouse brain and other tissues. Nevertheless, only the SSTR2 PCR product was amplified from granuloma cell RNA. The nucleotide sequence of the granuloma SSTR2 PCR product from inflammatory cells is identical to the CBA murine brain SSTR2 cDNA sequence. Granuloma-derived T cell lines, FACS-isolated granuloma CD4+ T cells, thymocytes, splenocytes, and cloned T cell lines all contain mRNA for SSTR2 by reverse transcription PCR. Moreover, both SSTR2A and the splice variant SSTR2B can be amplified from dispersed granuloma cells, granuloma T cell lines, thymocytes, and splenocytes. This is the first demonstration that inflammatory cells produce mRNA for an authentic somatostatin receptor. It is probable that the lymphocyte SSTR2 receptor mediates somatostatin-induced modulation of IFN-gamma secretion.

Eosinophils within the healthy or inflamed human intestine produce substance P and vasoactive intestinal peptide

The purpose of this study was to show if inflammatory cells within healthy or diseased human intestinal mucosa produce some regulatory neuropeptides. First, inflammatory cells were isolated from the intestinal lamina propria of 11 patients with ulcerative colitis or Crohn's disease. Also collected were cells from anatomically normal intestine derived from five patients requiring bowel resection for diseases not related to inflammatory bowel disease. Extracts of these isolated cells contained authentic substance P (SP) and vasoactive intestinal peptide (VIP) as shown by RIA and their elution profiles on HPLC. Immunostaining of cells from nine of 13 additional patients localized immunoreactive SP and VIP to secretory granules within most mucosal eosinophils. No other cell types stained positive. Messenger RNA encoding SP and VIP was localized to lamina propria eosinophils by in situ hybridization. Mucosa inflammatory cells, from eight of nine more patients, cultured in vitro, released detectable amounts of VIP, but not SP. It is concluded that intestinal eosinophils produce SP and VIP. Since the eosinophils store and release more VIP than SP, it is possible that VIP is the preferred secretory product.

Molecular evidence that granuloma T lymphocytes in murine schistosomiasis mansoni express an authentic substance P (NK-1) receptor

Murine Schistosomiasis mansoni is a parasitic disease in which granulomas develop around the schistosome ova that lodge in the liver and intestines of the host. The granuloma eosinophils make substance P (SP), a cytokine with immunoregulatory properties. Within the granuloma SP can modulate IFN-gamma production through interaction with a substance P-like receptor. SP belongs to a family of hormones called tachykinins. Three mammalian tachykinins are SP, neurokinin A (substance K), and neurokinin B (neuromedin K). In humans and rats, there are at least three distinct tachykinin receptors designated NK-1, NK-2, and NK-3. The NK-1 receptor binds only SP with high affinity. Using reverse transcription-PCR, cDNA cloning, and sequence analysis, we showed that granulomas isolated from the liver of infected mice express an authentic SP (NK-1) receptor but have no detectable neurokinin A (NK-2) and neurokinin B (NK-3) receptor mRNA, as determined by PCR. CD4+ granuloma T lymphocytes, purified by FACS, express NK-1 receptor mRNA. Normal liver devoid of granulomas exhibited none of the three tachykinin receptor subclasses.

Molecular evidence that granuloma T lymphocytes in murine schistosomiasis mansoni express an authentic substance P (NK-1) receptor

Murine Schistosomiasis mansoni is a parasitic disease in which granulomas develop around the schistosome ova that lodge in the liver and intestines of the host. The granuloma eosinophils make substance P (SP), a cytokine with immunoregulatory properties. Within the granuloma SP can modulate IFN-gamma production through interaction with a substance P-like receptor. SP belongs to a family of hormones called tachykinins. Three mammalian tachykinins are SP, neurokinin A (substance K), and neurokinin B (neuromedin K). In humans and rats, there are at least three distinct tachykinin receptors designated NK-1, NK-2, and NK-3. The NK-1 receptor binds only SP with high affinity. Using reverse transcription-PCR, cDNA cloning, and sequence analysis, we showed that granulomas isolated from the liver of infected mice express an authentic SP (NK-1) receptor but have no detectable neurokinin A (NK-2) and neurokinin B (NK-3) receptor mRNA, as determined by PCR. CD4+ granuloma T lymphocytes, purified by FACS, express NK-1 receptor mRNA. Normal liver devoid of granulomas exhibited none of the three tachykinin receptor subclasses.

Substance P and somatostatin can modulate the amount of IgG2a secreted in response to schistosome egg antigens in murine schistosomiasis mansoni

Substance P (SP) and somatostatin 1-14 (SOM) have immunoregulatory properties. Cells within the granulomas of murine schistosomiasis mansoni make both. SP enhances, whereas SOM inhibits soluble egg Ag (SEA)-induced, IFN-gamma production. IFN-gamma is important during IgG2a isotype switching. Thus, we investigated whether SP or SOM could affect IgG2a production in murine schistosomiasis. Our results show that SEA and rIFN-gamma stimulate splenic IgG2a secretion in murine schistosomiasis. Moreover, SP at &gt; or = to 10(-10) M substantially increased both polyclonal as well as SEA-specific, IgG2a secretion from spleen cells challenged with SEA. However, cells exposed to SOM at &gt; or = 10(-10)M showed strong inhibition. Also, both SP and SOM modulated the frequency of IgG2a-producing cells. Splenic IgG2a production in response to SEA, SP, and SOM required the presence of Thy 1.2+ cells, whereas, rIFN-gamma- induced IgG2a synthesis did not. Also, experiments using irradiation lymphocytes showed that SP, SOM, or rIFN-gamma modulation of IgG2a release was not dependent on cell proliferation. The highly specific SP receptor antagonist, CP-96,345, completely inhibited the effect of SP but not SOM on IgG2a release. This suggests that SP acted through an authentic NK-1 receptor and that SOM required a different receptor interaction. Granuloma cells secreted IgG2a constitutively. Yet, neither SEA, SP, SOM, rIFN-gamma, nor blocking anti-IFN-gamma mAb could modulate this constitutive IgG2a release during short term culture conditions. Moreover, the IgG2a secretion also continued in the absence of Thy 1.2+ lymphocytes. However, mice treated with CP-96,345 or octreotide (SOM agonist) in vivo produced granulomas that made little or no IgG2a. Spleen cell experiments showed that SEA, SP, SOM, and rIFN-gamma could only affect SEA-induced, IgG2a production during early stages of Ag stimulation. Thus, unlike the spleen, it is probable that the granulomas contain mostly activated B cells that have completed switch recombination.

Substance P and somatostatin can modulate the amount of IgG2a secreted in response to schistosome egg antigens in murine schistosomiasis mansoni

Substance P (SP) and somatostatin 1-14 (SOM) have immunoregulatory properties. Cells within the granulomas of murine schistosomiasis mansoni make both. SP enhances, whereas SOM inhibits soluble egg Ag (SEA)-induced, IFN-gamma production. IFN-gamma is important during IgG2a isotype switching. Thus, we investigated whether SP or SOM could affect IgG2a production in murine schistosomiasis. Our results show that SEA and rIFN-gamma stimulate splenic IgG2a secretion in murine schistosomiasis. Moreover, SP at > or = to 10(-10) M substantially increased both polyclonal as well as SEA-specific, IgG2a secretion from spleen cells challenged with SEA. However, cells exposed to SOM at > or = 10(-10)M showed strong inhibition. Also, both SP and SOM modulated the frequency of IgG2a-producing cells. Splenic IgG2a production in response to SEA, SP, and SOM required the presence of Thy 1.2+ cells, whereas, rIFN-gamma- induced IgG2a synthesis did not. Also, experiments using irradiation lymphocytes showed that SP, SOM, or rIFN-gamma modulation of IgG2a release was not dependent on cell proliferation. The highly specific SP receptor antagonist, CP-96,345, completely inhibited the effect of SP but not SOM on IgG2a release. This suggests that SP acted through an authentic NK-1 receptor and that SOM required a different receptor interaction. Granuloma cells secreted IgG2a constitutively. Yet, neither SEA, SP, SOM, rIFN-gamma, nor blocking anti-IFN-gamma mAb could modulate this constitutive IgG2a release during short term culture conditions. Moreover, the IgG2a secretion also continued in the absence of Thy 1.2+ lymphocytes. However, mice treated with CP-96,345 or octreotide (SOM agonist) in vivo produced granulomas that made little or no IgG2a. Spleen cell experiments showed that SEA, SP, SOM, and rIFN-gamma could only affect SEA-induced, IgG2a production during early stages of Ag stimulation. Thus, unlike the spleen, it is probable that the granulomas contain mostly activated B cells that have completed switch recombination.

Granuloma eosinophils enhance IL-5 production by lymphocytes from mice infected with Schistosoma mansoni

IL-5 is essential for granuloma eosinophilia in mice infection with schistosomiasis. The granulomas constitutively make IL-5 that originates from granuloma CD4+ T lymphocytes. This observation prompted us to learn whether non-T cell elements in the granuloma can promote constitutive IL-5 production. Neither granuloma eosinophils nor spleen cells from infected mice constitutively produced detectable levels of IL-5. Yet, mixing spleen cells with granuloma eosinophils resulted in spontaneous IL-5 secretion without promoting IL-4 production. Moreover, the admixed cultures were more responsive to anti-CD3 or soluble egg Ag than were cultures containing spleen cells alone. IL-5 ELISPOT assays in Transwell chambers showed that the cellular origin of IL-5 in the admixed cultures was the spleen cells, and that the phenomenon did not require cell-to-cell contact with granuloma eosinophils. Also, admixed cultures of granuloma eosinophils and spleen cells released less IL-5 in the presence of mAb that specifically blocked the biologic activity of either IL-2, IL-2R, or IAk. However, adding rIL-2 to spleen cell cultures at concentrations up to 100 U/ml could not stimulate secretion of IL-5. Because eosinophil supernatants contained no IL-2 as assessed by CTLL-2 bioassay, the release of IL-5 in response to eosinophils was not likely secondary to eosinophil secretion of IL-2. Thus, it appears that eosinophils produce a soluble substance that, with IL-2 and ongoing class II MHC/TCR interaction, enhances lymphocyte IL-5 output.

Granuloma eosinophils enhance IL-5 production by lymphocytes from mice infected with Schistosoma mansoni

IL-5 is essential for granuloma eosinophilia in mice infection with schistosomiasis. The granulomas constitutively make IL-5 that originates from granuloma CD4+ T lymphocytes. This observation prompted us to learn whether non-T cell elements in the granuloma can promote constitutive IL-5 production. Neither granuloma eosinophils nor spleen cells from infected mice constitutively produced detectable levels of IL-5. Yet, mixing spleen cells with granuloma eosinophils resulted in spontaneous IL-5 secretion without promoting IL-4 production. Moreover, the admixed cultures were more responsive to anti-CD3 or soluble egg Ag than were cultures containing spleen cells alone. IL-5 ELISPOT assays in Transwell chambers showed that the cellular origin of IL-5 in the admixed cultures was the spleen cells, and that the phenomenon did not require cell-to-cell contact with granuloma eosinophils. Also, admixed cultures of granuloma eosinophils and spleen cells released less IL-5 in the presence of mAb that specifically blocked the biologic activity of either IL-2, IL-2R, or IAk. However, adding rIL-2 to spleen cell cultures at concentrations up to 100 U/ml could not stimulate secretion of IL-5. Because eosinophil supernatants contained no IL-2 as assessed by CTLL-2 bioassay, the release of IL-5 in response to eosinophils was not likely secondary to eosinophil secretion of IL-2. Thus, it appears that eosinophils produce a soluble substance that, with IL-2 and ongoing class II MHC/TCR interaction, enhances lymphocyte IL-5 output.

Substance P modulates antigen-induced, IFN-gamma production in murine Schistosomiasis mansoni

In murine Schistosomiasis mansoni, granuloma eosinophils make SP. We investigated whether SP affects lymphokine secretion in murine schistosomiasis. SP at &gt; or = 10(-10) M, and other tachykinins at much higher concentrations, substantially increased IFN-gamma secretion from spleen or granuloma inflammatory cells primed in vitro by suboptimal stimulatory concentrations of egg Ag or mitogen. Cells receiving maximal antigenic or mitogenic stimulation were affected marginally. Also, tachykinins induced no IFN-gamma from resting cells receiving no Ag or mitogen stimulation. There are three distinct tachykinin receptors, called NK-1, NK-2 and NK-3. SP binds the NK-1 receptor with highest affinity. Specific NK-1 receptor antagonists blocked all tachykinin-induced, IFN-gamma secretion. An NK-2 receptor inhibitor had no effect. Thus, SP and other tachykinins were acting through an NK-1 receptor. Inflammatory cells from 4-day-old granulomas cultured in vitro secrete IFN-gamma. Yet, there was no measurable IFN-gamma when SP receptor antagonists were added to the cultures. Moreover, animals treated in vivo with the NK-1 receptor antagonist CP-96,345 produced smaller granulomas. This suggested that endogenous SP may be necessary for normal induction of granuloma IFN-gamma secretion and a normal granulomatous response. Granuloma macrophages make somatostatin (SOM) that can decrease IFN-gamma secretion. Yet, IFN-gamma secretion was unaffected when both SP and SOM were in the cell cultures. In conclusion, SP modulates Ag-driven IFN-gamma secretion through a NK-1 receptor. Also, SP and SOM may be components of a natural circuit within inflammation that regulates IFN-gamma production.

Substance P modulates antigen-induced, IFN-gamma production in murine Schistosomiasis mansoni

In murine Schistosomiasis mansoni, granuloma eosinophils make SP. We investigated whether SP affects lymphokine secretion in murine schistosomiasis. SP at > or = 10(-10) M, and other tachykinins at much higher concentrations, substantially increased IFN-gamma secretion from spleen or granuloma inflammatory cells primed in vitro by suboptimal stimulatory concentrations of egg Ag or mitogen. Cells receiving maximal antigenic or mitogenic stimulation were affected marginally. Also, tachykinins induced no IFN-gamma from resting cells receiving no Ag or mitogen stimulation. There are three distinct tachykinin receptors, called NK-1, NK-2 and NK-3. SP binds the NK-1 receptor with highest affinity. Specific NK-1 receptor antagonists blocked all tachykinin-induced, IFN-gamma secretion. An NK-2 receptor inhibitor had no effect. Thus, SP and other tachykinins were acting through an NK-1 receptor. Inflammatory cells from 4-day-old granulomas cultured in vitro secrete IFN-gamma. Yet, there was no measurable IFN-gamma when SP receptor antagonists were added to the cultures. Moreover, animals treated in vivo with the NK-1 receptor antagonist CP-96,345 produced smaller granulomas. This suggested that endogenous SP may be necessary for normal induction of granuloma IFN-gamma secretion and a normal granulomatous response. Granuloma macrophages make somatostatin (SOM) that can decrease IFN-gamma secretion. Yet, IFN-gamma secretion was unaffected when both SP and SOM were in the cell cultures. In conclusion, SP modulates Ag-driven IFN-gamma secretion through a NK-1 receptor. Also, SP and SOM may be components of a natural circuit within inflammation that regulates IFN-gamma production.

Granuloma T lymphocytes in murine schistosomiasis mansoni have somatostatin receptors and respond to somatostatin with decreased IFN-gamma secretion

The granulomas of mice infected with Schistosoma mansoni for 8 wk have macrophages that secrete somatostatin 1-14 (SOM). Within the granuloma, SOM has no known function. To uncover the possible significance of SOM produced within this granulomatous inflammation, we sought SOM receptors on distinct cellular components of the granuloma to identify cells targeted for SOM action. [125I]SOM 1-14 bound to dispersed granuloma inflammatory cells specifically and reversibly. Scatchard analysis suggested one receptor type (kDa 4.28 x 10(-9) M). Octreotide, a stable SOM derivative, displaced radioligand (kDa 1.01 x 10(-10) M), but SOM 1-28, substance P, and vasoactive intestinal peptide did not. The SOM receptor localized exclusively to a subset of granuloma CD4+ T lymphocytes. Using IL-5 and IFN-gamma ELISA, it was shown that granuloma T cells can secrete appreciable IL-5 and IFN-gamma when stimulated with Ag or mitogen. Both SOM and octreotide at concentrations as low as 10(-10) M substantially decreased IFN-gamma secretion from Ag or mitogen-stimulated T cells, but at concentrations as high as 10(-6) did not affect IL-5 production. Octreotide administered to animals in vivo decreased the intensity of the granulomatous response. Thus, some granuloma T cells have SOM 1-14 receptors. SOM 1-14, a product of granuloma macrophages, may participate in regulation of the granulomatous response by modulating the secretion of some lymphokines. Octreotide, a clinically useful SOM analog, mimics the action of SOM on the immune system.

Granuloma T lymphocytes in murine schistosomiasis mansoni have somatostatin receptors and respond to somatostatin with decreased IFN-gamma secretion

The granulomas of mice infected with Schistosoma mansoni for 8 wk have macrophages that secrete somatostatin 1-14 (SOM). Within the granuloma, SOM has no known function. To uncover the possible significance of SOM produced within this granulomatous inflammation, we sought SOM receptors on distinct cellular components of the granuloma to identify cells targeted for SOM action. [125I]SOM 1-14 bound to dispersed granuloma inflammatory cells specifically and reversibly. Scatchard analysis suggested one receptor type (kDa 4.28 x 10(-9) M). Octreotide, a stable SOM derivative, displaced radioligand (kDa 1.01 x 10(-10) M), but SOM 1-28, substance P, and vasoactive intestinal peptide did not. The SOM receptor localized exclusively to a subset of granuloma CD4+ T lymphocytes. Using IL-5 and IFN-gamma ELISA, it was shown that granuloma T cells can secrete appreciable IL-5 and IFN-gamma when stimulated with Ag or mitogen. Both SOM and octreotide at concentrations as low as 10(-10) M substantially decreased IFN-gamma secretion from Ag or mitogen-stimulated T cells, but at concentrations as high as 10(-6) did not affect IL-5 production. Octreotide administered to animals in vivo decreased the intensity of the granulomatous response. Thus, some granuloma T cells have SOM 1-14 receptors. SOM 1-14, a product of granuloma macrophages, may participate in regulation of the granulomatous response by modulating the secretion of some lymphokines. Octreotide, a clinically useful SOM analog, mimics the action of SOM on the immune system.

Murine mucosal T cells have VIP receptors functionally distinct from those on intestinal epithelial cells

Reports suggest that vasoactive intestinal peptide (VIP) binds to lymphocytes and modulates immune responses. The intestines are richly innervated with VIP-producing nerves. Thus, VIP from nerves or other sources may participate in mucosal immunoregulation. To explore this hypothesis further, murine intestinal mucosal inflammatory cells were scrutinized for functional VIP receptors. An [125I]VIP competitive binding assay characterized VIP receptors. Unfractionated lamina propria inflammatory cells bound [125I]VIP specifically. This binding was abrogated by T cell depletion. The VIP receptor on lamina propria T cells was of a single class with a Kd of 9.08 x 10(-9) M. It bound PHI and other peptide analogs poorly. The intestinal epithelial cell had a high-affinity VIP receptor (Kd 4.17 x 10(-10) M) that bound one VIP analog with moderate affinity. Both VIP and ConA stimulated mucosal inflammatory cells to release interleukin-5 (IL-5). Mucosal inflammatory cells depleted of T cells did not release IL-5 in response to VIP or ConA. It is concluded that: (1) some murine mucosal T lymphocytes have VIP receptors that may be distinct from those displayed on mucosal epithelial cells; (2) VIP affects mucosal T lymphocyte function.

Vasoactive intestinal peptide stimulates T lymphocytes to release IL-5 in murine schistosomiasis mansoni infection

In murine schistosomiasis, granulomas form around ova deposited in the liver and intestines of infected mice. The granulomas have eosinophils that produce vasoactive intestinal peptide (VIP) and T cells that display VIP receptors. IL-5 is a lymphokine important for the development and maturation of eosinophils. It seemed plausible that VIP, released from eosinophils, may interact with lymphocyte VIP receptors and modulate IL-5 production as part of a feedback regulatory circuit. Thus, we determined whether granuloma T cells make IL-5 and whether VIP modulates IL-5 production. Isolated granuloma cells enriched for T lymphocytes spontaneously released IL-5. Culture of these cells in the presence of VIP increased IL-5 secretion. Spleen cells were also studied. Spleen cells from infected mice did not spontaneously release IL-5 or express IL-5 mRNA and VIP did not stimulate these resting spleen cells to produce this IL. However, these cells did express IL-5 mRNA and secreted IL-5 in response to Con A or soluble egg Ag. VIP could not appreciably modulate IL-5 release when cells were cultured with VIP and the Ag or mitogen. Spleen cells washed free of Con A ceased IL-5 secretion within 24 h. These preactivated splenic T cells resumed vigorous IL-5 secretion in response to either Con A or VIP. Yet only Con A prominently induced IL-5 mRNA expression. VIP was an effective stimulus at concentrations equal to or above the kDa of the VIP receptor on both splenic and granuloma T cells (10(-8) M). It is concluded that, in murine schistosomiasis, VIP invokes IL-5 release from activated T cells that are not undergoing immediate TCR stimulation.

Vasoactive intestinal peptide stimulates T lymphocytes to release IL-5 in murine schistosomiasis mansoni infection

In murine schistosomiasis, granulomas form around ova deposited in the liver and intestines of infected mice. The granulomas have eosinophils that produce vasoactive intestinal peptide (VIP) and T cells that display VIP receptors. IL-5 is a lymphokine important for the development and maturation of eosinophils. It seemed plausible that VIP, released from eosinophils, may interact with lymphocyte VIP receptors and modulate IL-5 production as part of a feedback regulatory circuit. Thus, we determined whether granuloma T cells make IL-5 and whether VIP modulates IL-5 production. Isolated granuloma cells enriched for T lymphocytes spontaneously released IL-5. Culture of these cells in the presence of VIP increased IL-5 secretion. Spleen cells were also studied. Spleen cells from infected mice did not spontaneously release IL-5 or express IL-5 mRNA and VIP did not stimulate these resting spleen cells to produce this IL. However, these cells did express IL-5 mRNA and secreted IL-5 in response to Con A or soluble egg Ag. VIP could not appreciably modulate IL-5 release when cells were cultured with VIP and the Ag or mitogen. Spleen cells washed free of Con A ceased IL-5 secretion within 24 h. These preactivated splenic T cells resumed vigorous IL-5 secretion in response to either Con A or VIP. Yet only Con A prominently induced IL-5 mRNA expression. VIP was an effective stimulus at concentrations equal to or above the kDa of the VIP receptor on both splenic and granuloma T cells (10(-8) M). It is concluded that, in murine schistosomiasis, VIP invokes IL-5 release from activated T cells that are not undergoing immediate TCR stimulation.