[Persistence of the Salmonella enteritidis recombinant strain with expressed HBc antigen in mice and macrophage culture]

The behavior of S. enteritidis recombinant strain E-23/pKDNA(3.1) with HBc antigen expressed by the eukaryotic promoter (DNA vaccine) in the body of mice after their infection per rectum and in the culture of macrophages was studied. The expression of HBc was shown to lead to the loss of the capacity of salmonellae for persistence in parenteral lymphoid tissue and for inducing the formation of anti-HBc antibodies. The study of the interaction of salmonellae with the macrophage culture revealed that the synthesis of HBc antigen inhibited the intracellular multiplication of salmonellae.

Dynamics of CD4+CD25+ T cells in spleens and mesenteric lymph nodes of mice infected with Schistosoma japonicum

CD4+CD25+ T cells play a major role in modulating immune response, but few reports have been published about schistosomiasis. Here, we investigated the changes in CD4+CD25+ T cell populations in spleens and mesenteric lymph nodes of mice infected with Schistosoma japonicum. The proportions of CD4+CD25+ T cells in total CD4+ T cells were analyzed by flow cytometry. CD25 and Foxp3 expression was measured by real-time quantitative polymerase chain reaction. The suppressive activities of CD4+CD25+ T cells were detected by in vitro proliferation of splenocytes. Evidence showed that the percentage of CD4+CD25+ T cells was the same as controls 3 weeks post-infection. At the acute stage of infection, the percentage decreased significantly. However, at the chronic stage of infection, it rebounded to normal levels or even higher. The expression of the CD25 and Foxp3 showed gradual increase along with the infection progress. In vitro experiment also showed the strong suppressive effect of CD4+CD25+ T cells, isolated during the chronic stage, on proliferation of the CD25- splenocytes. This is the first time that the dynamics of CD4+CD25+ T cell populations was demonstrated in mice infected with schistosomiasis. In conclusion, our data indicated that CD4+CD25+ cells might be involved in the immune modulation during S. japonicum infection, which enhances current knowledge of the mechanisms of the immuno-downregulation and re-infection in schistosomiasis.

Mesenteric lymph nodes at the center of immune anatomy

The surface of the intestinal mucosa is constantly assaulted by food antigens and enormous numbers of commensal microbes and their products, which are sampled by dendritic cells (DCs). Recent work shows that the mesenteric lymph nodes (MLNs) are the key site for tolerance induction to food proteins and that they also act as a firewall to prevent live commensal intestinal bacteria from penetrating the systemic immune system.

Involvement of 4-1BB (CD137)-4-1BBligand interaction in the modulation of CD4 T cell-mediated inflammatory colitis

4-1BB ligand (4-1BBL) expressed on antigen-presenting cells interacts with 4-1BB on activated T cells (especially CD8+ cells) and co-stimulates the latter to secrete cytokines and to proliferate. The role of 4-1BB-4-1BBL interaction was studied here in a model of colitis based on naive CD4+ T cell transfer to SCID mice, a disease model in which CD8 cells do not take part. We found that CD4+ T cells from 4-1BB-deficient mice, after transfer in SCID mice, proliferated more rapidly compared to wild-type CD4+ T cells. Mice reconstituted with naive CD4+ T cells from 4-1BB-deficient mice developed colitis, however, with a mixed Th1/Th2 response, in contrast to the Th1-type response in mice reconstituted with wild-type naive CD4+ T cells. Importantly, this altered cytokine response did not temper colitis severity. Although it has been reported previously that 4-1BB co-stimulation may contribute to regulatory T cell functioning, we found that CD4+CD25+ regulatory T cells from 4-1BB-deficient mice were perfectly able to prevent naive CD4+ T cell-induced colitis. In conclusion, our data provide evidence that 4-1BB-4-1BBL interaction modulates the effector CD4+ T cell-driven immune response and cytokine production in experimental colitis without affecting regulatory T cell function.

INFLUENCE OF CYCLOOXYGENASE INHIBITORS ON GUT IMMUNE CELL DISTRIBUTION AND APOPTOSIS RATE IN EXPERIMENTAL SEPSIS

The aim of this study was to determine if cyclooxygenase (COX) inhibitors influence immune cell distribution in the small intestinal mucosa and mesenteric lymph nodes (MLNs), the grade of mucosal damage, and the rate of apoptosis in septic rats. The effects induced by a selective COX-2 inhibitor (SC-236) were compared with those of a nonselective COX-1 and -2 inhibitor (indomethacin). Cecal ligation and puncture (CLP), CLP + SC-236 p.o, and CLP + indomethacin p.o, were evaluated. Animals were harvested 6 and 24 h after CLP, respectively. The concentration of proinflammatory cytokines was higher in ascitic fluid than in blood. CLP + SC-236 attenuated IL-6 in plasma and in ascitic fluid and CLP + indomethacin augmented TNF-alpha in ascitic fluid compared with CLP at 6 h. CLP + SC-236 gave a lesser degree of mucosal damage compared with CLP alone or with indomethacin at 6 and 24 h (P < 0.05). Untreated CLP had significant reductions in the number of T lymphocytes in the villi and increases of macrophages in the mucosa and MLNs compared with controls (P < 0.05). CLP + indomethacin decreased T lymphocytes in the villi and MLNs. CLP caused an enhanced apoptosis in the mucosa compared with controls (P < 0.05), pretreatment with COX inhibitors did not significantly change this. Both COX inhibitors enhanced apoptosis in MLNs and attenuated the increase of macrophages in mucosa and MLNs (P < 0.05). It is proposed that the increased apoptosis and the decrease in T cells in the mucosa may be causally related. Apoptosis of lymphocytes may impair the immunologic defense in sepsis. Furthermore, loss of intestinal epithelial cells may compromise bowel wall integrity and facilitate translocation.

Sphingosine-1-phosphate agonists increase macrophage homing, lymphocyte contacts, and endothelial junctional complex formation in murine lymph nodes

The sphingosine-1-phosphate (S1P) receptor agonist, phosphorylated FTY720 (FTY-P), causes lymphopenia, lymphocyte sequestration in mesenteric lymph nodes (MLNs), and immunosuppression. Using multiple techniques to analyze MLN cells harvested from mice treated with S1P receptor agonists, we saw a redistribution of lymphocytes out of nodal sinuses and an expansion of follicles. Although changes in circulating monocytes were not observed with overnight exposure to FTY720, we saw a significant increase in S1P receptor 1 (S1P1)-expressing CD68+ macrophages in subcapsular sinuses of FTY-P-treated MLNs. This was confirmed by quantitative analysis of F4/80+ cells in MLN suspensions. The sinus volume and number of S1P1-positive cells within sinuses were also increased by FTY-P. High endothelial venules and lymphatic endothelium expressed high levels of S1P1, and treatment with FTY-P resulted in intense staining and colocalization of CD31, beta-catenin, and zona occludens 1 in junctions between sinus cells. Transmission electron microscopy showed that FTY-P greatly reduced lymphocyte microvilli and increased cell-cell contacts in the parenchyma. Immunoelectron microscopy revealed that intranodal lymphocytes lacked surface expression of S1P1, whereas S1P1 was evident on the surface and within the cytoplasm of macrophages, endothelial cells, and stromal cells. This subcellular pattern of intranodal receptor distribution was unchanged by treatment with FTY-P. We conclude that S1P1 agonists have profound effects on macrophages and endothelial cells, in addition to inducing lymphopenia.

Mast cell activation by stress

Mental or emotional stress has been shown to cause mast cell degranulation in several different tissues. Several lines of experimental evidence indicate that stress, working through the sympathetic nervous system, or the hypothalamus-pituitary-adrenal axis, stimulates peripheral nerves to release neuropeptides that bind to receptors on the mast cells, causing them to degranulate. In order to investigate the effects of stress on mast cell degranulation, it is necessary to first establish a reproducible animal model of stress (in this case, rat) and also to ensure that the control animals do not show any signs of stress. This procedure requires a great deal of care and attention because the methods used by many institutions to house laboratory rodents, do in fact cause them stress. This topic is addressed in this chapter. In addition, two histological techniques are described to visualize connective tissue and mucosal mast cells and to assess their degree of degranulation.

In vivo CpG DNA/toll-like receptor 9 interaction induces regulatory properties in CD4+CD62L+ T cells which prevent intestinal inflammation in the SCID transfer model of colitis

BACKGROUND AND METHODS

Cytosin-guanosin dinucleotide (CpG) motifs of bacterial DNA are known to be potent activators of innate immunity. We have shown previously that administration of CpG containing oligodeoxynucleotide (CpG-ODN) to mice before the onset of dextran sodium sulphate induced colitis ameliorated colitis and inhibited induction of proinflammatory cytokines. To investigate the possible involvement of CD4(+) T cells in the prophylactic CpG-ODN effects, we used the SCID transfer model of colitis.

RESULTS

CD4(+)CD62L(+) T cells from CpG-ODN treated donors did not induce significant intestinal inflammation in SCID recipients, in contrast with control cells. Additionally, cotransfer of these cells with CD4(+)CD62L(+) cells from normal mice protected recipient animals from colitis, indicating regulatory activity. Also, CD4(+)CD62L(+) cells from toll-like receptor 9 deficient animals induced a significantly more severe colitis in SCID recipients than cells from wild-type littermate controls, suggesting a similar protective role of "endogenous" bacterial DNA leading to a less "aggressive" phenotype of these cells. There was no detectable difference in regulatory T cell surface markers between aggressive and attenuated cell pools but attenuated cell pools showed reduced proliferation in vitro and in vivo and produced less interferon gamma, interleukin (IL)-5, and IL-6 after anti-CD3 stimulation.

CONCLUSIONS

Collectively, our data support the concept that both endogenous bacterial DNA and exogenously supplied CpG motifs of bacterial DNA induce regulatory properties in CD4(+) T cells. Therefore, bacterial DNA derived from the normal gut flora may contribute essentially to the homeostasis between effector and regulatory immune mechanisms in healthy individuals to protect them from chronic intestinal inflammation.

Treatment of mice with the anticoccidial drug Toltrazuril does not interfere with the development of a specific cellular intestinal immune response to Eimeria falciformis

Immunity against Eimeria-infections is highly specific and it depends on cell-mediated effector mechanisms. Infections of BALB/c mice with 1,000 sporulated oocysts of Eimeria falciformis led to protection against challenge infections. Treatment with the anti-coccidium Toltrazuril, during primary infection, terminated the ongoing disease and did not interfere with the establishment of protective immunity against challenge infections. Mesenteric lymph node cells of infected, treated as well as non-treated and challenged BALB/c mice, showed a similar proliferation upon stimulation with parasite antigen. In contrast, neither cells of the Peyer's patches, intraepithelial lymphocytes, nor spleen cells responded to stimulation with parasite antigens. Cells from all compartments and of all investigated groups proliferated and released the cytokines IFN-gamma and IL-4 in response to the mitogen Concanavalin A. The number of cells releasing IFN-gamma or IL-4 was not dependent on the status of infection or previous treatment with Toltrazuril. The serum IgG response against total sporozoite antigens of individual mice showed that in addition, a systemic humoral response developed in infected mice, independent of a previous drug treatment, although the specific IgG antibody concentration was higher in non-treated mice. Thus, Toltrazuril does not impair the parasite specific intestinal cellular and systemic antibody response and does not prevent the development of protection against challenge infection.

Intragastric administration of Mycobacterium vaccae inhibits severe pulmonary allergic inflammation in a mouse model

BACKGROUND

Coexistence with harmless microorganisms such as lactobacilli, saprophytic mycobacteria and some helminths, throughout evolution, may have shaped the host immune system. Exposure to such organisms may have therapeutic benefits by triggering immunoregulatory mechanisms that control inappropriate immune responses to self, gut contents or allergens.

OBJECTIVE

We determined whether treatment with Mycobacterium vaccae by gavage influences the host immune response both locally and systemically. We also investigated whether delivery by this route prevents severe symptoms of disease in a murine model of pulmonary allergic inflammation.

RESULTS

A single intragastric administration of M. vaccae induced a transient increase in the production of IL-10 and IFN-gamma by mesenteric lymph nodes cells and splenocytes. In addition, in a mouse model of pulmonary allergic inflammation, a single treatment with M. vaccae by gavage not only diminished the total cellular infiltrate and the eosinophilic component induced by subsequent intratracheal allergen challenge, but also biased local and systemic cytokine production towards IL-10. Delivery of M. vaccae by gavage was as effective as subcutaneous treatment.

CONCLUSION

This is the first report to suggest that heat-killed mycobacteria can down-regulate symptoms of allergic inflammation by the intragastric route. These data suggest an alternative route of treatment with M. vaccae for patients with allergic conditions.

L-selectin and beta7 integrin on donor CD4 T cells are required for the early migration to host mesenteric lymph nodes and acute colitis of graft-versus-host disease

The homing receptors L-selectin and alpha4beta7 integrin facilitate entry of T cells into the gut-associated organized lymphoid tissues such as the mesenteric lymph nodes and Peyer patches. We studied the impact of inactivation of genes encoding these receptors on the ability of purified donor CD4+ T cells to induce acute lethal graft-versus-host disease (GVHD) associated with severe colitis in irradiated major histocompatibility complex (MHC)-mismatched mice. Whereas lack of expression of a single receptor had no significant impact on the severity of colitis and GVHD, the lack of expression of both receptors markedly ameliorated colitis and early deaths observed with wild-type (WT) T cells. The changes in colitis and GVHD were reflected in a marked reduction in the early accumulation of donor T cells in the mesenteric lymph nodes and subsequently in the colon. The purified WT donor CD4+ T cells did not accumulate early in the Peyer patches and failed to induce acute injury to the small intestine. In conclusion, the combination of CD62L and beta7 integrin is required to induce acute colitis and facilitate entry of CD4+ donor T cells in the mesenteric nodes associated with lethal GVHD in allogeneic hosts.

Wheat protein-induced proinflammatory T helper 1 bias in mesenteric lymph nodes of young diabetes-prone rats

AIMS/HYPOTHESIS

Type 1 diabetes is the result of an inflammatory T helper 1 (Th1) lymphocyte-mediated beta cell destructive process. The majority of diabetes-prone BioBreeding (BBdp) rats fed wheat protein-based diets, such as NTP-2000, develop type 1 diabetes and display a mild coeliac-like enteropathy. Mesenteric lymph nodes (MLNs), which drain the gut, are the major inductive site where dietary antigens are recognised in the gut-associated lymphoid tissue (GALT). We hypothesised that this compartment could be a site of abnormal wheat protein-induced Th1 cell activation.

METHODS

MLN cells were isolated from BBdp and BB control (BBc) rats that were fed NTP-2000 or a hydrolysed casein (HC)-based diet at ages that pre-date classic insulitis. The inflammatory status, phenotype and proliferation of these cells in response to wheat protein were determined.

RESULTS

The expression ratio of T-bet : Gata3, master transcription factors for Th1 and Th2 cytokines, was increased in the MLN from NTP-2000-fed BBdp rats compared with that from BBc rats, mainly due to decreased Gata3 expression. CD3(+)CD4(+)IFN-gamma(+) T cells were more prevalent in the MLN of wheat-fed BBdp rats, but remained at control levels in BBdp rats fed a diabetes-retardant HC diet. BBdp MLN cells proliferated in response to wheat protein antigens in a specific, dose-dependent manner, and >93% of cells were CD3(+)CD4(+) T cells. This proliferation was associated with a low proportion of CD4(+)CD25(+) T cells and a high proportion of dendritic cells in the MLN of BBdp rats.

CONCLUSIONS/INTERPRETATION

Before insulitis is established, the MLNs of wheat-fed BBdp rats contain an unusually high proportion of Th1 cells that proliferate specifically in response to wheat protein antigens.

Mesenteric Th1 polarization and monocyte TNF-alpha production: first steps to systemic inflammation in rats with cirrhosis

A systemic inflammatory state with increased circulating tumor necrosis factor alpha (TNF-alpha) has been related to the bacterial infection susceptibility and hemodynamic derangement of patients with cirrhosis. We compared the activation status of immune cell subpopulations defined by 4-color cytometry in mesenteric and peripheral lymph nodes and blood of rats with CCl(4)-cirrhosis to define the immune response initiation site, the T-cell and monocyte contribution to pro-inflammatory cytokine production, as well as the pathogenic role of enteric bacteria in the cirrhosis immune response. Th1 cells and monocytes were expanded in the mesenteric nodes (P < .001) and blood (P < .001) of rats with cirrhosis, and activated to produce interferon gamma (P < .0001) and TNF-alpha (P < .0001), respectively. The greater numbers of recently activated CD134(+) Th cells in mesenteric nodes compared with blood, the correlation between their numbers in mesenteric nodes and blood (r = 0.66, P < .001), and the expansion of activated CD45RC(-) Th cells, which are unable to re-enter lymph nodes, in mesenteric nodes but not in blood or axillary nodes points to mesenteric nodes as the origin site of activated Th cells. Abrogation of bacterial translocation by bowel decontamination reduced the number of activated Th cells and monocytes, and normalized interferon gamma production by Th cells and TNF-alpha production by monocytes in mesenteric nodes and blood, respectively. In conclusion, in cirrhosis, enteric bacteria start off an orchestrated immune response cascade in mesenteric nodes involving Th1 polarization and monocyte activation to TNF-alpha production. Later, the recirculation of these activated effector immune cells into blood promotes systemic inflammation.

Critical protective role for annexin 1 gene expression in the endotoxemic murine microcirculation

The inflammatory response is a protective process of the body to counteract xenobiotic penetration and injury, although in disease this response can become deregulated. There are endogenous biochemical pathways that operate in the host to keep inflammation under control. Here we demonstrate that the counterregulator annexin 1 (AnxA1) is critical for controlling experimental endotoxemia. Lipopolysaccharide (LPS) markedly activated the AnxA1 gene in epithelial cells, neutrophils, and peritoneal, mesenteric, and alveolar macrophages--cell types known to function in experimental endotoxemia. Administration of LPS to AnxA1-deficient mice produced a toxic response characterized by organ injury and lethality within 48 hours, a phenotype rescued by exogenous application of low doses of the protein. In the absence of AnxA1, LPS generated a deregulated cellular and cytokine response with a marked degree of leukocyte adhesion in the microcirculation. Analysis of LPS receptor expression in AnxA1-null macrophages indicated an aberrant expression of Toll-like receptor 4. In conclusion, this study has detailed cellular and biochemical alterations associated with AnxA1 gene deletion and highlighted the impact of this protective circuit for the correct functioning of the homeostatic response to sublethal doses of LPS.

Mesenteric B cells centrally inhibit CD4+ T cell colitis through interaction with regulatory T cell subsets

Inflammatory bowel disease reflects an aberrant mucosal CD4+ T cell response to commensal enteric bacteria. In addition to regulatory T cell subsets, recent studies have revealed a protective role of B cells in murine CD4+ T cell colitis, but the relationship of their action to T cell immunoregulation is unknown. Here we report that mesenteric lymph node (MLN) B cells protect mice from colitis induced by Galphai2-/- CD4+ T cells. Protection required the transfer of both B cells and CD8alpha+ T cells; neither cell type alone was sufficient to inhibit CD4+ T cell-mediated colitis. Similar results were also observed in colitis induced by CD4+CD45RBhi T cells. Immunoregulation was associated with localization of B cells and expansion of CD4-CD8- CD3+NK1.1+ T cells in the secondary lymphoid compartment, as well as expansion of CD4+CD8alpha+ T cells in the intestinal intraepithelial compartment. MLN B cells from Galphai2-/- mice were deficient in a phenotypic subset and failed to provide cotransfer colitis protection. These findings indicate that protective action of B cells is a selective trait of MLN B cells acquired through a Galphai2-dependent developmental process and link B cells with the formation of regulatory T cells associated with mucosal immune homeostasis.

Platelet-activating factor and kinin-dependent vascular leakage as a novel functional activity of the soluble terminal complement complex

The infrequent occurrence of septic shock in patients with inherited deficiencies of the terminal complement components experiencing meningococcal disease led us to suspect that the terminal complement complex is involved in vascular leakage. To this end, the permeabilizing effect of the cytolytically inactive soluble terminal complement complex (SC5b-9) was tested in a Transwell system measuring the amount of fluorescein-labeled BSA (FITC-BSA) leaked through a monolayer of endothelial cells. The complex caused increased permeability to FITC-BSA after 15 min as opposed to the prompt response to bradykinin (BK). The effect of SC5b-9 was partially reduced by HOE-140 or CV-3988, two selective antagonists of BK B2 and platelet-activating factor receptors, respectively, and was completely neutralized by the mixture of the two antagonists. Also, DX-88, a specific inhibitor of kallikrein, partially inhibited the activity of SC5b-9. The permeabilizing factor(s) released after 30 min of incubation of endothelial cells with SC5b-9 caused a prompt leakage of albumin like BK. Intravital microscopy confirmed both the extravasation of circulating FITC-BSA across mesenteric microvessels 15 min after topical application of SC5b-9 and the complete neutralization by the mixture of HOE-140 and CV-3988. SC5b-9 induced opening of interendothelial junctions in mesenteric endothelium documented by transmission electron microscopy.

Immunoproliferative small intestinal disease (IPSID): a model for mature B-cell neoplasms

Immunoproliferative small intestinal disease (IPSID) was recently added to the growing list of infectious pathogen-associated human lymphomas. Molecular and immunohistochemical studies demonstrated an association with Campylobacter jejuni. IPSID is a variant of the B-cell lymphoma of mucosa-associated lymphoid tissue (MALT), which involves mainly the proximal small intestine resulting in malabsorption, diarrhea, and abdominal pain. Geographically, IPSID is most prevalent in the Middle East and Africa. IPSID lymphomas reveal excessive plasma cell differentiation and produce truncated alpha heavy chain proteins lacking the light chains as well as the first constant domain. The corresponding mRNA lacks the variable heavy chain (V(H)) and the constant heavy chain 1 (C(H)1) sequences and contains deletions as well as insertions of unknown origin. The encoding gene sequence reveals a deletion of V region and parts of C(H)1 domain. Cytogenetic studies demonstrated clonal rearrangements involving predominantly the heavy and light chain genes, including t(9;14) translocation involving the PAX5 gene. Early-stage IPSID responds to antibiotics (30%-70% complete remission). Most untreated IPSID patients progress to lymphoplasmacytic and immunoblastic lymphoma invading the intestinal wall and mesenteric lymph nodes, and may metastasize to a distant organ. IPSID lymphoma shares clinical, morphologic, and molecular features with MALT lymphoma, lymphoplasmacytic lymphoma, and plasma cell neoplasms.

Accelerated ischemia/reperfusion-induced injury in autoimmunity-prone mice

Natural Abs have been implicated in initiating mesenteric ischemia/reperfusion (I/R)-induced tissue injury. Autoantibodies have affinity and self-Ag recognition patterns similar to natural Abs. We considered that autoimmunity-prone mice that express high titers of autoantibodies should have enhanced I/R-induced injury. Five-month-old B6.MRL/lpr mice displayed accelerated and enhanced intestinal I/R-induced damage compared with 2-mo-old B6.MRL/lpr and age-matched C57BL/6 mice. Similarly, older autoimmune mice had accelerated remote organ (lung) damage. Infusion of serum IgG derived from 5-mo-old but not 2-mo-old B6.MRL/lpr into I/R resistant Rag-1-/- mice rendered them susceptible to local and remote organ injury. Injection of monoclonal IgG anti-DNA and anti-histone Abs into Rag-1-/- mice effectively reconstituted tissue injury. These data show that like natural Abs, autoantibodies, such as anti-dsDNA and anti-histone Abs, can instigate I/R injury and suggest that they are involved in the development of tissue damage in patients with systemic lupus erythematosus.

Combined alcohol and burn injury differentially regulate p-38 and ERK activation in mesenteric lymph node T cell

Recent studies from our laboratory have suggested that acute alcohol ingestion prior to burn injury enhances gut bacterial translocation by suppressing T cell-mediated intestinal immune defense. To determine the mechanism responsible for suppressed T cell function, we examined the activation of mitogen-activated protein kinases (MAPK) members p-38 and ERK-1/2. Both p-38 and ERK-1/2 are known to play a significant role in the T cell proliferation and their cytokine production. Rats were gavaged with ethanol to achieve a blood alcohol level of approximately 100 mg/dl, before they were subjected to a 25% total body surface area burn injury. Two days after injury, rats were sacrificed and mesenteric lymph node (MLN) T cells were isolated and their ability to proliferate in response to anti-CD3 was determined. For p-38 and ERK-1/2 determination, T cells were divided into two groups. Cells in one group were stimulated with anti-CD3 for 3 min and lysed. The cells in the second group were cultured for approximately 18 h in the presence of anti-CD3 and lysed. MAPK status in 18-h cultured cells allowed us to determine whether or not the changes in p-38 and ERK-1/2 are transient or persist in the proliferating cells. Two days after injury, anti-CD3-mediated MLN T cell proliferation was more suppressed in rats gavaged with alcohol prior to burn injury compared to rats receiving either burn injury alone or sham-injured rats regardless of their exposure. Western blot analyses showed significant inhibition of ERK-1/2 phosphorylation in both freshly isolated and 18-h cultured T cells from alcohol and burn-injured rats compared to the sham rat T cells. The inhibition of p-38 phosphorylation in T cells derived from alcohol and burn-injured rats was found to be transient as no significant difference in p-38 phosphorylation was noted between the 18 h incubated MLN T cells of sham and alcohol and burn-injured rats. Taken together, our findings suggest that low levels of ERK-1/2 activation is likely to play a significant role in MLN T cell proliferative suppression in alcohol and burn-injured rats.

Role of CD8+ and CD4+ T lymphocytes in jejunal mucosal injury during murine giardiasis

T-cell-mediated pathogenesis has been documented in various idiopathic and microbially induced intestinal disorders. Diffuse microvillous shortening seen in giardiasis is responsible for disaccharidase insufficiencies and malabsorption of electrolytes, nutrients, and water. Other mucosal changes include crypt hyperplasia and increased numbers of intraepithelial lymphocytes (IEL). A recent report using an athymic mouse model of infection showed that these epithelial injuries were dependent on T cells. The aim of the present study was to identify which subset of superior mesenteric lymph node (SMLN) T cells were responsible for mucosal alterations in giardiasis. CD4+ and CD8+ T cells, as well as whole lymphocyte populations, were isolated from SMLN of Giardia muris-infected mice for adoptive transfer. Jejunal segments of recipient mice were assessed for brush border ultrastructure, sucrase activity, crypt/villus ratio, and IEL numbers. Mice that received enriched CD8+ and whole SMLN lymphocytes, but not CD4+ T cells, from infected donors showed diffuse shortening of microvilli, loss of brush border surface area, impaired sucrase activity, and increased crypt/villus ratios compared to respective controls. Transfer of whole SMLN lymphocytes, as well as enriched CD4+ or CD8+ T cells, from infected donors led to increased IEL numbers in the recipient jejunum. The findings indicate that loss of intestinal brush border surface area, reduced disaccharidase activities, and increased crypt/villus ratios in giardiasis are mediated by CD8+ T cells, whereas both CD8+ and CD4+ SMLN T cells regulate the influx of IEL.

Peripheral CD4 T cells rapidly accumulate at the host: parasite interface during an inflammatory Th2 memory response

Memory peripheral Th2 immune responses to infectious pathogens are not well studied due to the lack of suitable models and the difficulty of assessing Th2 cytokine expression at sites of inflammation. We have examined the localized immune response to a nematode parasite that encysts in the small intestine. An unexpected architecture was observed on day 4 of the memory response, with granulocytes and macrophages infiltrating the cyst and CD4(+), TCR-alphabeta(+) T cells surrounding the cyst. Laser capture microdissection analysis showed a pronounced CD4-dependent Th2 cytokine pattern at the cyst region only during the memory response, demonstrating that the Th2 memory response is readily distinguished from the primary response by the rapid accumulation of Th2 effector cells at the host:parasite interface.

Retractile mesenteritis: report of a case

Retractile mesenteritis is a rare idiopathic inflammatory process of the mesenteric adipose tissue. A 58-year-old woman who presented with acute abdominal pain and vomiting underwent laparotomy for a small bowel obstruction of unknown etiology. The laparotomy showed dilated small bowel loops and multiple tumor-like fibrous plaques in the mesentery. Histological examination revealed nonspecific chronic inflammatory processes of the mesentery. The computed tomography finding of increased density of the mesenteric fat, known as the "fat-ring sign," in a patient with small bowel obstruction and no surgical history would suggest this rare diagnosis.

The quantity and diversity of infectious viruses in various tissues of SHIV-infected monkeys at the early and AIDS stages

To detect the major sites of viral replication in immunodeficiency virus-infected individuals, we quantified proviral DNA and infectious viruses using quantitative PCR and a plaque assay, respectively, in various tissues of SHIV(KU-2)-infected monkeys in the early and AIDS stages of infection. Compared the quantity of infectious virus among PBMC and the lymphoid tissues, the mesenteric lymph node had the largest number of infectious viruses at the AIDS stage more than at the early stage of infection. These results suggested that the gastrointestinal tract was a major site of viral replication. In the brain, proviral DNA was detected at the early and AIDS stage of infection, but infectious viruses were detected at only the AIDS stage. Moreover, we analyzed the nucleotide sequences of the env V3 region in infectious virus clones isolated from each plaque. The viruses in the lymphoid tissues of the monkey that developed AIDS diverged from the inoculated virus and had the same three amino acid substitutions. However, the viruses in the brain were almost identical to the inoculated virus, suggesting that the virus entered the brain early after infection and persisted without replication and genetic diversion until the AIDS stage.

CD4+ effector T cell distributionin vivo: TGF-β1/TGF-β receptor II interaction during activation mediates accumulation in the target tissue by preferential proliferation

CD4(+) effector T cells generated in mesenteric lymph nodes (mLN) leave into the blood. Although they enter many tissues, mLN effector T cells are later found preferentially in the gut,the drainage area of mLN. We show in the rat that this is not an intrinsic property of mLN T cells. Instead, within the mLN milieu T cells are instructed by cytokines such as transforming growth factor beta 1 (TGF-beta 1) to up-regulate TGF-beta receptor II (TGF-beta RII) during activation. This enables effector T cells to continue proliferation upon subsequent contact with TGF-beta 1 in mLN and gut, and to accumulate in the lymph node draining area, the most likely site of pathogen invasion.

Intestinal epithelial exosomes carry MHC class II/peptides able to inform the immune system in mice

BACKGROUND

Intestinal epithelial cells secrete exosome-like vesicles. The aim of this study was to characterise murine intestinal epithelial exosomes and to analyse their capacity to inform the immune system in vivo in mice.

METHODS

Epithelial exosomes were obtained from the murine epithelial cell line MODE K incubated in the presence or absence of interferon gamma (IFN-gamma) together with pepsin/trypsin ovalbumin hydrolysate (hOVA) to mimic luminal digestion. Exosomes isolated from MODE K conditioned media (EXO-hOVA and EXO-hOVA-IFN) were characterised by western blot, peptide mapping, and mass spectrometry. They were injected intraperitoneally to C3H/HeN mice to test their immunocompetence.

RESULTS

MODE K epithelial exosomes displayed major histocompatibility complex (MHC) class I and class II (upregulated by IFN-gamma) molecules and tetraspan proteins (CD9, CD81, CD82) potentially involved in the binding to target cells. A33 antigen, an Ig-like molecule highly specific for intestinal epithelial cells, was enriched in exosomes and was also found in mice mesenteric lymph nodes, suggesting exosome migration towards the gut associated lymphoid tissues. Intraperitoneal injection of EXO-hOVA or EXO-hOVA-IFN did not induce humoral or cellular tolerance to OVA in mice. In contrast, exosomes obtained after incubation with IFN-gamma (EXO-hOVA-IFN), bearing abundant MHC class II/OVA complexes, induced a specific humoral immune response.

CONCLUSIONS

Epithelial exosomes are antigen presenting vesicles bearing MHC class II/peptide complexes that prime for an immunogenic rather than tolerogenic response in the context of a systemic challenge. In the intestine, both the mucosal microenvironment and local effector cells are probably key players in determining the outcome of the immune response to exosome derived epitopes.

Contrasting roles for IL-10 in protective immunity to different life cycle stages of intestinal nematode parasites

Expulsion of the gastro-intestinal nematode Trichinella spiralis is associated with a pronounced mastocytosis mediated by a T helper (Th) 2 type response involving interleukin (IL)-4 and IL-13. Here we demonstrate that IL-10 is a key regulator of protective immune responses against T. spiralis in vivo. IL-10 knockout mice or normal mice treated with a neutralizing anti-IL-10 receptor antibody are highly susceptible to a primary T. spiralis infection and show significantly delayed adult worm expulsion. Depletion of IL-10 resulted in elevated Th1 and Th2 cytokine responses but significantly reduced numbers of mucosal mast cells in the jejunum. Interestingly, the increase in IFN-gamma detected in the absence of IL-10 resulted in increased immunity to larval stages. Hence, IL-10 has a negative effect on immunity to the tissue dwelling larval stages of T. spiralis but plays a significant biological role as an in vivo regulator of intestinal mast cell responses and is crucially involved in protection against adult stages of intestinal parasites in vivo.

Effect of dietary pectin on the production of immunoglobulins and cytokines by mesenteric lymph node lymphocytes in mouse colitis induced with dextran sulfate sodium

The present study explores the dietary effect of pectin on the MLN lymphocyte functions of mice with dextran sulfate sodium (DS)-induced colitis. We found that the immunoglobulin (Ig)A level in mesenteric lymph node (MLN) lymphocytes was high, while the IgE level was lower, in mice fed with pectin than in those fed with cellulose. Interestingly, the fecal IgA concentration of the pectin-fed mice was significantly higher than that of the cellulose-fed mice. The concentrations of interferon-gamma and interleukin (IL)-2 treated with concanavalin A (ConA) were significantly higher in the pectin-fed group than in the cellulose-fed group. Although dietary pectin did not affect the IL-4 and IL-10 levels, the activation-induced IL-4 and IL-10 secretion was lower in MLN cells of the pectin-fed mice than of the cellulose-fed mice following DS-induced colitis. Based on these findings, we propose that the effect of dietary pectin on mice with DS-induced colitis is mediated by the manipulation of Th1 cells. Furthermore, the inhibitory effect of IL-4 and IL-10 by dietary pectin may play an important role in promoting a change in Th1/Th2 balance toward Th1-dominant immunity.

Levamisole mucosal adjuvant activity for a live attenuated Escherichia coli oral vaccine in weaned pigs

The present study tested the hypothesis that levamisole exerts its immunopotentiating activity in weaned pigs vaccinated against colibacillosis by priming the lymphocytes and macrophages in the mesenteric lymph node (MLN). Ten weaned piglets were used and allocated into two equal groups. The experimental group was intramuscularly primed with levamisole at an immunostimulatory dose of 2.5 mg/kg given daily, in three consecutive days, and controls received saline according to the same schedule. Both groups were orally vaccinated with the vaccinal Escherichia coli strain on day 0 and challenged with the virulent E. coli strain 7 days later. All pigs were killed on postchallenge day 6. Upon virulent challenge the health status of the two groups was evaluated by clinical observations, and expression of CD25, SWC7 and SWC9 activation antigens by MLN and spleen T and B cells and macrophages, respectively, was tested using flow cytometry. Priming by levamisole significantly contributed to the effectiveness of a live attenuated oral vaccine against porcine postweaning colibacillosis, as evidenced by a good health status of primed vaccinated vs. un-primed vaccinated pigs. The CD3+, CD25+ and SWC9+ MLN but not spleen T cells and macrophages increased in experimental vs. control pigs, implying that levamisole exerts its potentiating activity in the MLN by augmenting both recruitment and activation of cells that participate in cell-mediated immunity.

The initial immune response during experimental cysticercosis is of the mixed Th1/Th2 type

The immunological events that occur during the initial stages of experimental cysticercosis are not known. The studies presented here examined the cytokines produced by peritoneal exudate cells (PECs), splenocytes and mesenteric lymph node (MLN) cells during the first week of infection with larval Taenia crassiceps in BALB/cJ mice. Proliferation assays determined that the earliest time when antigen-specific responses could be measured was 5 days post-infection. Concanavalin A (ConA) stimulation of host cells elicited an initial burst of IL-4 production at 24 h of infection and ConA-stimulated Th2-type cytokine production is predominant by 7 days post-infection. Thus, there are responses at day 1 of infection that seem to promote a Th2-type response. Stimulation of MLN cells, splenocytes and PECs with larval antigens supported previous reports of mixed Th1/Th2-type cytokine production with increases in interleukin (IL)-4, IL-10 and interferon (IFN)-gamma. Ex vivo IFN-gamma production by PECs from infected mice was increased at 3, 5 and 7 days post-infection, whereas at these times reduced ex vivo IL-10 production was observed. This ex vivo IFN-gamma response preceded an increasing IL-10 production by PECs between 3 and 7 days post-infection in parasite-specific and ConA-induced proliferation assays. Thus, infection with larval T. crassiceps results in an initial response mediated by IFN-gamma that is quickly followed by an increase in IL-10 production and subsequent reduction in the amount of IFN-gamma being produced.

Effects of wogonin, wogonoside, and 3,5,7,2',6'-pentahydroxyflavone on chemical mediator production in peritoneal exduate cells and immunoglobulin E of rat mesenteric lymph node lymphocytes

Wogonin (WG), wogonoside (WGS), and 3,5,7,2',6'-pentahydroxyl flavanone (PHF) were isolated from Scutellaria baicalensis, and their effects on histamine, leukotriene B(4) (LTB(4)), and immunoglobulin E (IgE) were examined in rats, observing for a manifestation of a type I allergic reaction. WG and WGS in the amounts of 10 and 100 microM were shown to markedly inhibit histamine release in cells stimulated with calcium ionophore A23187 or compound 48/80. PHF exerted inhibitory activity only at 100 microM. In the case of LTB(4), WG, WGS and PHF markedly inhibited LTB(4) production at the concentration of 100 microM. We also find that the increase in the IgE content induced by concanavalin A (ConA) was alleviated in the presence WG and WGS, while the inhibitory effect of PHF was much weaker. However, the magnitude of inhibitory effect observed on the content of lipid peroxidation induced by ConA was in order of PHF > WG > WGS, with PHF being the strongest. Interestingly, WG and WGS with the methoxyl group strongly inhibited histamine and IgE production, whereas PHF with the hydroxyl group in the B ring was much stronger than WG and WGS against lipid peroxidation. Based on data, it was concluded that the flavonoid components, WG, WGS, and PHF, may block a common pathway for the release of histamine and LTB(4), and that the IgE level is responsible for the lipid peroxidation induced by ConA.

Encapsulation of recombinant adenovirus into alginate microspheres circumvents vector-specific immune response

Pre-existing immunity against adenoviruses may compromise the efficacy of adenoviral vectors for vaccination and gene therapy. The purpose of this study was to determine whether encapsulation of adenovirus recombinants into biodegradable alginate microparticles could circumvent the vector-specific immune response. Mice were immunized either intranasally (i.n.) or intraperitoneally (i.p.) with human adenovirus type 5 (HAd5), resulting in the development of virus-specific antibodies. Immunized and nai;ve mice were inoculated with AdCA36lacZ (an E1-deleted HAd5 recombinant containing the bacterial beta-galactosidase (LacZ) gene), encapsulated (E) into alginate microparticles, or nonencapsulated (NE) ie, as a virus suspension. LacZ expression in animals immunized once (1x) or twice (2x) with HAd5 and subsequently inoculated with NE-AdCA36lacZ (NE-Z) was significantly (P<0.001) reduced compared to those levels observed in NE-Z inoculated nai;ve mice, suggesting that the immune response against the vector adversely affected transgene expression. In contrast, there was only slight reduction (P>0.05) in LacZ expression in mice immunized 1x or 2x with HAd5 that were subsequently inoculated with E-AdCA36lacZ (E-Z) compared to those levels obtained in E-Z inoculated nai;ve animals. Similar results were obtained with i.n. or i.p. inoculated animals. These results indicate that microencapsulation of recombinant adenovirus effectively circumvented the vector-specific immune response.

Trauma-hemorrhage-induced neutrophil priming is prevented by mesenteric lymph duct ligation

Our objective in this study was to test the hypothesis that priming of neutrophils (PMN) in vivo by trauma-hemorrhagic shock (T/HS) is mediated by factors carried in intestinal lymph that prime PMNs by enhancing their responses to inflammatory mediators. Previous studies have shown that T/HS-induced lung injury is mediated by factors contained in mesenteric lymph and that ligation of the main mesenteric lymph duct (LDL) can prevent T/HS-induced lung injury. Since T/HS-induced lung injury is associated with PMN infiltration, one mechanism underlying this protective effect may be the prevention of PMN priming and activation. Therefore, we assessed the ability of T/HS to prime PMN responses to inflammatory agonists, and the ability of mesenteric lymph duct division to protect against such T/HS-induced PMN priming in an all-rat system. PMN were collected from male rats 6 h after laparotomy (trauma) plus hemorrhagic shock (30 mmHg for 90 min; T/HS) or trauma plus sham shock (T/SS). Uninstrumented rats were used as controls (UC). In a second set of experiments, rats were subjected to T/HS with or without mesenteric lymph duct division. PMN were then stimulated with chemokine (GRO, MIP-2) and lipid (PAF) chemoattractants, and cell calcium flux was used to quantify responses to those agonists. T/SS primed PMN responses to GRO, MIP-2. and PAF in comparison to UC rats, but the addition of shock (T/HS) amplified PMN priming in a significant manner, especially in response to GRO. Mesenteric lymph duct division prior to T/HS diminished PMN priming to the levels seen in T/SS. This reversal of priming was significant for GRO and GRO/MIP-2 given sequentially, with the other agonist regimens showing similar trends. The results support the concept that trauma and hemorrhagic shock play important additive roles in inflammatory PMN priming. Entry of gut-derived inflammatory products into the circulation via mesenteric lymph seems to play a dominant role in mediating the conversion of physiologic shock insults into immunoinflammatory PMN priming. Shock-induced gut lymph priming enhances PMN responses to many important chemoattractants, most notably the chemokines, and mesenteric lymph duct division effectively reverses such priming to priming levels seen in trauma without shock.

Microvascular cell death in spontaneously hypertensive rats during experimental inflammation

OBJECTIVE

Chronic hypertension is associated with an increased risk for tissue injury that may be mediated in part by endothelium and inflammatory cells. To clarify a possible underlying mechanisms, we examined leukocyte migration in the microcirculation and concomitant parenchymal cell death.

METHODS

The mesentery of spontaneously hypertensive rats (SHRs) and their normotensive controls, Wistar Kyoto (WKY) rats, was examined with digital fluorescence microscopy after topical stimulation with an inflammatory mediator (f-met-leu-phe, 10(-8)M). The migratory pathways of individual leukocytes were traced, and at the same time cell death was detected by use of a life-death indicator (propidium iodide) over a period of 3 hours.

RESULTS

Both WKY and SHR had a progressively increasing number of leukocytes migrating across the endothelium in postcapillary venules into the tissue parenchyma. But parenchymal cell death was detected in a random pattern in the mesentery tissue, without correlation to the migratory positions of the leukocytes. Although mature SHR rats (about 17 weeks) exhibited the same level of cell death as age-matched WKY rats, older WKY rats (about 30 weeks) had significantly lower levels of cell death, whereas the SHR rats maintained the same number of parenchymal cell death as mature animals.

CONCLUSIONS

These results suggest that in the presence of an inflammatory mediator, the SHR may exhibit a stronger response to an inflammatory mediator than normotensive WKY rats in a fashion that is age, but not blood pressure, dependent. Parenchymal cell death does not correlate with migration of activated leukocytes at the microvascular level.

Annexin 1 localisation in tissue eosinophils as detected by electron microscopy

BACKGROUND

Human and rodent leukocytes express high levels of the glucocorticoid-inducible protein annexin 1 (ANXA1) (previously referred to as lipocortin 1). Neutrophils and monocytes have abundant ANXA1 levels.

AIM

We have investigated, for the first time, ANXA1 ultrastructural expression in rat eosinophils and compared it with that of extravasated neutrophils. The effect of inflammation (carrageenin peritonitis) was also monitored.

METHODS

Electron microscopy was used to define the sub-cellular localisation of ANXA1 in rat eosinophils and neutrophils extravasated in the mesenteric tissue. A pair of antibodies raised against the ANXA1 N-terminus (i.e. able to recognise intact ANXA1, termed LCPS1) or the whole protein (termed LCS3) was used to perform the ultrastructural analysis.

RESULTS

The majority of ANXA1 was localised in the eosinophil cytosol (approximately 60%) and nucleus (30-40%), whereas a small percentage was found on the plasma membrane (< 10%). Within the cytosol, the protein was equally distributed in the matrix and in the granules, including those containing the typical crystalloid. The two anti-ANXA1 antibodies gave similar results, with the exception that LCPS1 gave a lower degree of immunoreactivity in the plasma membrane. Inflammation (i.e. carrageenin injection) produced a modest increase in eosinophil-associated ANXA1 reactivity (significant only in the cytoplasm compartment). Extravasated neutrophils, used for comparative purposes, displayed a much higher degree of immunoreactivity for the protein.

CONCLUSION

We describe for the first time ANXA1 distribution in rat eosinophil by ultrastructural analysis, and report a different protein mobilisation from extravasated neutrophils, at least in this acute model of peritonitis.

Encapsulated Bifidobacterium bifidum potentiates intestinal IgA production

We asked whether Bifidobacterium bifidum regulates the synthesis of IgA by mucosal lymphoid cells. B. bifidum alone, but not Clostridium perfringens, significantly induced total IgA and IgM synthesis by both mesenteric lymph nodes (MLN) and Peyer's patch (PP) cells. We, further, investigated the mucosal antibody production following peroral administration of B. bifidum to mice. Ingested B. bifidum significantly increased the number of Ig (IgM, IgG, and IgA) secreting cells in the culture of both MLN and spleen cells. Nonetheless, B. bifidum itself does not induce the own specific antibody responses, implying that B. bifidum does not provoke unnecessary immune reaction. Subsequently, it was found that encapsulation of B. bifidum further augments the total IgA production in the culture of both MLN and spleen cells. Finally, we found that the immuno-stimulating activity of B. bifidum is due to its cellular components but not due to any actively secreting component(s) from bacteria.

Lymphoproliferative responses and protection in conventional piglets inoculated orally with virulent or attenuated porcine epidemic diarrhoea virus

Lymphocyte proliferative responses were evaluated in mucosal (mesenteric lymph nodes) and systemic (spleen and blood) lymphoid tissues of conventional piglets inoculated with the virulent or attenuated isolates of porcine epidemic diarrhoea virus (PEDV) strain CV-777 and challenged 21 days later with the virulent isolate of the same virus. A lymphoproliferative assay was developed in which mononuclear cells isolated from lymphoid tissues at different postinoculation and postchallenge days underwent a secondary in vitro stimulation with semipurified antigen obtained from PEDV-infected cell cultures. Vigorous lymphocyte proliferative responses were detected in the pigs inoculated with the virulent PEDV at postinoculation days 4-21, especially in the mesenteric lymph nodes and the blood; however, in the spleen this response was lower and less regular. The pigs inoculated with the attenuated virus showed a less intense response, the higher lymphocyte proliferation also corresponded to the mononuclear cells from mesenteric lymph nodes. Lymphocyte proliferation responses showed high correlations with protection against homologous challenge with virulent PEDV, and this correlation was higher in the gut associated lymphoid tissues (mesenteric lymph nodes). The cell proliferation response detected in blood mirrored that detected in the mesenteric lymph nodes, and showed also good correlation with protection. The results confirm that T-cell-helper function, assessed by lymphocyte proliferation responses, contributes to establishing a protective immune response against PEDV infections.

Hyperosmolarity abrogates neutrophil cytotoxicity provoked by post-shock mesenteric lymph

Hypertonic saline (HTS) resuscitation inhibits acute lung injury in animal models of shock, but some argue this may simply represent more efficient fluid resuscitation. Inflammatory mediators within mesenteric lymph have been identified as a link between splanchnic hypoperfusion and acute respiratory distress syndrome (ARDS). We hypothesize that HTS resuscitation abrogates post-shock lymph-mediated neutrophil (PMN) priming and PMN-mediated human endothelial cell cytotoxicity. Mesenteric lymph was collected from rats (n = 5) before (control), during non-lethal hemorrhagic shock, defined as a mean arterial pressure (MAP) of 40 mmHg for 30 min, and after resuscitation (shed blood + 2 x lactated Ringers (LR) versus 7.5% NaCl, 4 cc/kg, over 5 min). Isolated human PMNs were primed with physiologic concentrations (5% v:v) of lymph either from animals resuscitated with LR or HTS and activated with either PMA or fMLP. In a separate set of experiments, human PMNs were primed with LR lymph after incubation with HTS (180 mM NaCl). The maximal rate of superoxide production was measured by reduction of cytochrome C. In addition, the effect of HTS pretreatment on PMN adherence to human pulmonary microvascular endothelial cells (HMVEC) and PMN-mediated cytotoxicity was determined after lymph-mediated PMN priming. PHSML primed isolated PMNs above buffer controls and pre-shock lymph in a normotonic environment; HTS resuscitation abrogated this effect. HTS preincubation of isolated PMNs inhibited PHSML-induced PMN priming, adherence to HMVECs, and PMN-mediated HMVEC cytotoxicity. Hypertonic resuscitation (HTS) abrogates PHSML pniming of the PMN and PMN-mediated HMVEC cytotoxicity. Furthermore, incubation of PMNs in clinically relevant HTS (180 mM NaCl) prevents PHSML PMN priming and PMN:HMVEC interactions. These studies suggest inhibition of PMN signal transduction is a mechanism whereby HTS resuscitation abrogates acute lung injury.

The dispersal of mucosal memory B cells: evidence from persistent EBV infection

We have used latent infection with the human herpesvirus Epstein-Barr virus to track the dispersal of memory B cells from the mucosal lymphoid tissue of Waldeyer's ring (tonsils/adenoids). EBV is evenly distributed between the memory compartments of Waldeyer's ring and the peripheral blood. However, it has an approximately 20-fold higher preference for Waldeyer's ring over the spleen or mesenteric lymph nodes. These observations are consistent with a model whereby the virus preferentially establishes persistent infection within memory B cells from Waldeyer's ring. The virus then colonizes the entire peripheral lymphoid system, at a low level, by trafficking with these memory B cells as they circulate through the body and back to Waldeyer's ring. This pathway may reflect that of normal memory B cells derived from nasopharyngeal and other mucosal lymph nodes.

Mesenteric lymph nodes are critical for the induction of high-dose oral tolerance in the absence of Peyer's patches

We have previously demonstrated the loss of oral tolerance (OT) in lymphotoxinalpha-/- (LTalpha-/-) and TNFalpha / lymphotoxinalpha deficient (TNFalpha / LTalpha-/-) mice which have defective Peyer's patches (PP) and lymph node (LN) development. We have now studied OT in BALB / c mice with differential defects of the gut-associated lymphoid tissue (GALT) caused by inhibition of LTbetaR signaling during fetal development. Treatment of pregnant mice with LTbetaR-IgG (LTbetaRIgG) and TNFR I55-IgG (TNFR55IgG) abrogates the formation of PP (LTbetaRIgG) or of PP and mesenteric LN (MLN) (LTbetaRIgG / TNFRIgG) without genetically deleting the respective cytokine pathways. OT was readily induced in mice without PP but retaining MLN (PP null / LN +). In contrast, OTcould not be induced in mice lacking both MLN and PP (PP null / MLN null) as shown by the inability of these mice to suppress IFN-gamma secretion or DTH reactions. We next assessed OT in 129 x B6 LTalpha-/- mice with and without MLN. Timed treatment of pregnant LTalpha-/- mice with an agonist anti-LTbetaR mAb induces formation of MLN but not of PP in LTalpha-/- mice. LN + LTalpha-/- mice developed OT while LN LTalpha-/- mice were resistant to OT induction. Taken collectively, the data show that in the presence of MLN PP are not required for OT induction and that the presence of MLN is sufficient for OT induction in the LTalpha-/- model.

A comparison of local and peripheral parasite-specific antibody production in different strains of mice infected with Trichuris muris

The serum parasite-specific antibody responses of different mouse strains infected with Trichuris muris reflect the nature of the T-helper response mounted by the host, in that resistant Th2-responding strains, such as BALB/K, produce immunoglobulin (Ig)G1 and susceptible predominantly Th1-responding strains, such as AKR, produce IgG2a and IgG1. However, the kinetics of antibody production in the sera, as determined by enzyme-linked immunosorbent assay, do not reflect infection status in that resistant strains can expel their worm burdens before antibodies are detectable in the sera. Here, we show that parasite-specific antibody production by in vitro lipopolysaccharide-stimulated mesenteric lymph node cells (MLN) not only correlate with serum antibody isotypes, but also follow expulsion kinetics. Additionally, the antibody levels seen locally match changes in absolute B220+ cell numbers in the MLN (determined by flow cytometry) and changes in MLN parasite-specific plasma cells in the MLN (determined by ELISPOT). These results show that B cell responses are tightly regulated locally in both resistant and susceptible strains of mice infected with T. muris.

Phenotypic and functional differences between NKT cells colonizing splanchnic and peripheral lymph nodes

NKT cells are considered unconventional T cells. First, they are restricted by a nonclassical MHC class I molecule, CD1d, which presents glycolipids; second, their TCR repertoire is very limited. After stimulation by their TCR, NKT cells rapidly release large amounts of cytokines, such as IL-4 and IFN-gamma. Little is known about NKT cells present in lymph nodes. In the present report we show that NKT cells are differently distributed in various lymph nodes and are, for instance, abundant in pancreatic and mesenteric lymph nodes of C57BL/6 mice and nonobese diabetic mice. The high frequency of NKT cells in splanchnic lymph nodes is not simply a consequence of inflammatory signals, as draining lymph nodes still contain low frequencies of NKT cells after IFA or CFA injections. NKT cells from splanchnic lymph nodes harbor a Vbeta repertoire similar to that of splenic and liver NKT cells, in contrast to peripheral NKT cells that are not biased toward Vbeta8 segments. Analysis of cytokine production by NKT cells from splanchnic lymph nodes reveals that they produce at least as much IL-4 as IFN-gamma, in contrast to NKT cells from other organs (spleen, liver, and peripheral lymph nodes), which produce much more IFN-gamma than IL-4. These specific features of NKT cells from splanchnic lymph nodes might explain their protective action against the development of pathogenic Th1 cells in type 1 diabetes.

Identification of multiple isolated lymphoid follicles on the antimesenteric wall of the mouse small intestine

We have revealed that 100-200 clusters, filled with closely packed lymphocytes, can be found throughout the length of the antimesenteric wall of the mouse small intestine. They are composed of a large B cell area, including a germinal center, and epithelia overlying the clusters contain M cells. A large fraction of B cells displays B220+ CD19+ CD23+ IgM(low)IgD(high)CD5(-)Mac-1(-) phenotype, and the composition of IgA+ B cells is smaller but substantial. To our knowledge, these clusters are the first identification of isolated lymphoid follicles (ILF) in mouse small intestine. ILF can be first detected at 7 (BALB/c mice) and 25 (C57BL/6 mice) days after birth, and lymphoid clusters equivalent in terms of cellular mass to ILF are present in germfree, athymic nude, RAG-2(-/-), TCR-beta(-/-), and Ig mu-chain mutant (mu(-/-)) mice, although c-kit+ cells outnumber B220+ cells in germfree and athymic nude mice, and most lymphoid residents are c-kit+ B220(-) in RAG-2(-/-), TCR-beta(-/-), and mu(-/-) mice. ILF develop normally in the progeny of transplacentally manipulated Peyer's patch (PP)-deficient mice, and decreased numbers of conspicuously atrophied ILF are present in IL-7Ralpha(-/-) PP(null) mice. Neither ILF nor PP are detectable in lymphotoxin alpha(-/-) and aly/aly mice that retain well-developed cryptopatches (CP) and thymus-independent subsets of intraepithelial T cells, whereas ILF, PP, CP, and thymus-independent subsets of intraepithelial T cells disappear from common cytokine receptor gamma-chain mutant mice. These findings indicate that ILF, PP, and CP constitute three distinct organized gut-associated lymphoid tissues that reside in the lamina propria of the mouse small intestine.

Intercellular cell adhesion molecule-1 regulates lymphocyte movement into intestinal microlymphatics of rat Peyer's patches

The objective of this study was to determine whether specific adhesion molecules modulate lymphocyte movement from Peyer's patches into intestinal microlymphatics. The fluorochrome acridine orange was injected via a micropipette into Peyer's patches to fill lymphatics. The flux of labeled lymphocytes into intestinal microlymphatics was monitored with intravital fluorescence microscopy. The lymphatic microvessels in the perifollicular area of Peyer's patches were filled with lymphocytes, most of which remained within the lymphatics. Some lymphocytes became detached and were drained into intestinal lymph. Administration of antibodies directed against ICAM-1 significantly increased lymphocyte flux into interfollicular lymphatics. The immunohistochemical study showed intense ICAM-1 expression on the lymphocytes densely packed in the lymphatics surrounding follicles in Peyer's patches. A large number of lymphocytes are normally sequestered in the lymphatic network of Peyer's patches. This sequestration of lymphocytes is largely mediated by ICAM-1-dependent cell-cell interactions.

CTA1-DD-immune stimulating complexes: a novel, rationally designed combined mucosal vaccine adjuvant effective with nanogram doses of antigen

Mucosally active vaccine adjuvants that will prime a full range of local and systemic immune responses against defined antigenic epitopes are much needed. Cholera toxin and lipophilic immune stimulating complexes (ISCOMS) containing Quil A can both act as adjuvants for orally administered Ags, possibly by targeting different APCs. Recently, we have been successful in separating the adjuvant and toxic effects of cholera toxin by constructing a gene fusion protein, CTA1-DD, that combines the enzymatically active CTA1-subunit with a B cell-targeting moiety, D, derived from Staphylococcus aureus protein A. Here we have extended this work by combining CTA1-DD with ISCOMS, which normally target dendritic cells and/or macrophages. ISCOMS containing a fusion protein comprising the OVA(323-339) peptide epitope linked to CTA1-DD were highly immunogenic when given in nanogram doses by the s.c., oral, or nasal routes, inducing a wide range of T cell-dependent immune responses. In contrast, ISCOMS containing the enzymatically inactive CTA1-R7K-DD mutant protein were much less effective, indicating that at least part of the activity of the combined vector requires the ADP-ribosylating property of CTA1. No toxicity was observed by any route. To our knowledge, this is the first report on the successful combination of two mechanistically different principles of adjuvant action. We conclude that rationally designed vectors consisting of CTA1-DD and ISCOMS may provide a novel strategy for the generation of potent and safe mucosal vaccines.

In situ demonstration of intraepithelial lymphocyte adhesion to villus microvessels of the small intestine

The recirculation of lymphocytes through the intestinal mucosa is important for specific immune defense, but the origin and differentiation of intraepithelial lymphocytes (IEL) are not fully understood. The present study therefore used intravital microscopy to investigate the migration of IEL to the villus mucosa and Peyer's patches of the small intestine. IEL were separated from inverted murine small intestine and mesenteric lymph node (MLN) T cells were also isolated. The adhesion of fluorescence-labeled lymphocytes to postcapillary venules (PCV) of Peyer's patches and arcade microvessels of small intestinal villi was observed after injection. In some experiments, the effect of antibodies against adhesion molecules on cell kinetics were investigated. IEL time-dependently accumulated in villus microvessels of the small intestine, whereas few MLN cells did. Few IEL adhered to the PCV of Peyer's patches. IEL were shown to express alpha(E)beta(7)-integrin but not L-selectin. The accumulation of IEL in villus archade was significantly inhibited by antibody against beta(7)-integrin or mucosal addressin cell adhesion molecules (MAdCAM)-1, but not by alpha(E)-integrin. The combined blocking of beta(7)-integrin and MAdCAM-1 further attenuated the sticking of IEL in this area, although it did not entirely block the IEL adherence. The adherence of CD4(+) or TCRalphabeta IEL to villus microvessels was significantly greater than that of CD4(-) or TCRgammadelta IEL. It was demonstrated in situ for the first time that IEL adhered selectively to the villus microvessels of the small intestine partly via beta(7) and MAdCAM-1.

Immune cell distribution in gut-associated lymphoid tissue and synthesis of IL-6 in experimental porcine peritonitis

This study aimed to evaluate the possibility to detect early changes in gut-associated lymphoid tissue related to an inflammatory response. Anaesthetised pigs were subjected to faecal peritonitis (n = 9) or to a sham procedure (n = 8). Blood from the vena cava and the superior mesenteric vein was repeatedly sampled, and the levels of interleukin-6 (IL-6) were analysed. Biopsies of the small intestine and mesenteric lymph nodes (MLNs), harvested at 300 min, were incubated with monoclonal antibodies specific for CD2 (T lymphocytes), IgM (B lymphocytes) and CD11a/CD18 (leucocyte adhesion molecule). The number of positive (+) cells was scored. During peritonitis, IL-6 increased significantly. Compared to controls, the number of CD2+ cells decreased, IgM+ cells tended to increase and CD11a/CD18+ cells increased in the mucosa during peritonitis. In MLNs, the number of cells positive for all studied markers increased during peritonitis. We conclude that peritonitis causes an inflammatory response in the gut reflected by changes in the distribution of immune cells in gut-associated lymphoid tissue and release of IL-6 to venous blood.

Intranasal immunization with SAG1 and nontoxic mutant heat-labile enterotoxins protects mice against Toxoplasma gondii

Effective protection against intestinal pathogens requires both mucosal and systemic immune responses. Intranasal administration of antigens induces these responses but generally fails to trigger a strong protective immunity. Mucosal adjuvants can significantly enhance the immunogenicities of intranasally administered antigens. Cholera toxin (CT) and heat-labile enterotoxin (LT) are strong mucosal adjuvants with a variety of antigens. Moreover, the toxicities of CT and LT do not permit their use in humans. Two nontoxic mutant LTs, LTR72 and LTK63, were tested with Toxoplasma gondii SAG1 protein in intranasal vaccination of CBA/J mice. Vaccination with SAG1 plus LTR72 or LTK63 induced strong systemic (immunoglobulin G [IgG]) and mucosal (IgA) humoral responses. Splenocytes and mesenteric lymph node cells from mice immunized with LTR72 plus SAG1, but not those from mice immunized with LTK63 plus SAG1, responded to restimulation with a T. gondii lysate antigen in vitro. Gamma interferon and interleukin 2 (IL-2) production by splenocytes and IL-2 production by mesenteric lymph node cells were observed in vitro after antigen restimulation, underlying a Th1-like response. High-level protection as assessed by the decreased load of cerebral cysts after a challenge with the 76K strain of T. gondii was obtained in the group immunized with LTR72 plus SAG1 and LTK63 plus SAG1. They were as well protected as the mice immunized with the antigen plus native toxins. This is the first report showing protection against a parasite by using combinations of nontoxic mutant LTs and SAG1 antigen. These nontoxic mutant LTs are now attractive candidates for the development of mucosally delivered vaccines.

Peripheral cytokine responses to Trichuris muris reflect those occurring locally at the site of infection

The study of human cellular immune responses to parasite infection under field conditions is very complex. Often, the only practical site from which to sample the cellular responses is the peripheral blood. Sampling peripheral blood lymphocytes (PBL) relies on the assumption that these peripheral responses accurately reflect the immune responses acting locally at the site of infection. This is a particularly important point for the human intestinal helminth Trichuris trichiura, which solely inhabits the cecum and large intestine and so will stimulate a localized immune response. Using the well-defined model of T. trichiura, T. muris in the mouse, we have demonstrated that the dominant cytokine responses of the mesenteric lymph nodes (MLN) can be detected by sampling PBL. Resistant mice which mount a type 2 cytokine response in their MLN had PBL producing interleukin-4 (IL-4), IL-5, and IL-9, with negligible levels of gamma interferon (IFN-gamma). Conversely, susceptible mice which mount a type 1 cytokine response in their MLN had PBL producing IFN-gamma and negligible levels of type 2 cytokines. We have also shown that the PBL are capable of mounting a functional immune response against T. muris. PBL from immune mice were capable of transferring immunity to T. muris-infected severe combined immunodeficient (C.B-17 scid/scid) mice. Sampling PBL responses is therefore a viable option for monitoring human intestinal immune responses during T. trichiura infection in the field.