Mucosal mast cell responses are not required for protection against infection with the murine nematode parasite Trichuris muris

The involvement of mucosal mast cells (MMC) in protection against infection with the murine nematode parasite Trichuris muris was studied in genetically mast cell-deficient WBB6F1-W/Wv mice and their normal littermates WBB6F1-+/+ mice. Expulsion of T. muris worms occurred in infected +/+ mice, whereas no worm expulsion was observed in infected W/Wv mice where the infection persisted until at least day 46 postinfection. No MMC responses were induced in either infected W/Wv or +/+ mice. Specific IgG1and IgG2a antibodies to T. muris excretory/secretory antigens were observed in infected W/Wv and +/+ mice, and antibody production showed similar kinetics. Interleukin 4 production by concanavalin A (Con A)-stimulated mesenteric lymph node cells (MLNC) was induced preferentially in infected +/+ mice. T. muris infection increased the levels of IFN-gamma produced by Con A-stimulated MLNC of infected W/Wv and +/+ mice, with the levels of IFN-gamma in infected W/Wv mice being higher than those in infected +/+ mice. Taken together, these results indicate that W/Wv and +/+ mice are susceptible and resistant to T. muris infection, respectively, and that MMC responses are not required for protective immunity.

Differential induction of adhesion molecule and chemokine expression by LTalpha3 and LTalphabeta in inflammation elucidates potential mechanisms of mesenteric and peripheral lymph node development

Lymphotoxin (LT) is a member of the proinflammatory TNF family of cytokines that plays a critical role in the development of lymphoid tissue. It has previously been reported that the presence of the LTalpha transgene under the control of the rat insulin promoter results in inflammation at the sites of transgene expression. LTalpha transgene expression results in expression of the adhesion molecules VCAM, ICAM, peripheral node addressin (a marker of peripheral lymph nodes), and mucosal addressin cellular adhesion molecule (a marker of mucosal lymphoid tissue, including mesenteric lymph nodes). In this study to determine the mechanisms by which LT promotes inflammation and lymphoid tissue organization, we analyzed the regulation of expression of adhesion molecules and chemokines in LT transgenic mice. The results demonstrate that LTalpha3 induces expression of the adhesion molecules VCAM, ICAM, and mucosal addressin cellular adhesion molecule as well as the chemokines RANTES, IFN-inducible protein-10, and monocyte chemotactic protein-1, while LTalphabeta is required for the induction of peripheral node addressin that may contribute to the recruitment of L-selectinhigh CD44low naive T cells. These data provide candidate mediators of LT-induced inflammation as well as potential mechanisms by which LTalpha and LTalphabeta may differentially promote the development of mesenteric and peripheral lymph nodes.

Lymph node germinal centers form in the absence of follicular dendritic cell networks

Follicular dendritic cell networks are said to be pivotal to both the formation of germinal centers (GCs) and their functions in generating antigen-specific antibody affinity maturation and B cell memory. We report that lymphotoxin beta-deficient mice form GC cell clusters in the gross anatomical location expected of GCs, despite the complete absence of follicular dendritic cell networks. Furthermore, antigen-specific GC generation was at first relatively normal, but these GCs then rapidly regressed and GC-phase antibody affinity maturation was reduced. Lymphotoxin beta-deficient mice also showed substantial B cell memory in their mesenteric lymph nodes. This memory antibody response was of relatively low affinity for antigen at week 4 after challenge, but by week 10 after challenge was comparable to wild-type, indicating that affinity maturation had failed in the GC phase but developed later.

Characterization of experimental Cryptosporidium parvum infection in IFN-gamma knockout mice

Severe cryptosporidial infections were produced in gamma interferon (IFN-gamma) knockout mice. Mean oocyst shedding increased from 332 to 30,717 oocysts/100 microliters of faecal suspension between day 4 and 9 after administration of 1 x 10(5) oocysts/mouse. No significant differences in oocyst shedding were observed in mice after being inoculated with 1 x 10(5), 1 x 10(4) or 1 x 10(3) oocysts/mouse (P > 0.05). Infected mouse weights decreased an average 3-4 g before death or euthanization. Histological studies revealed heavy parasite colonization in small intestinal epithelium (approximately 250 organisms/high-power field at x 400). Mesenteric lymph nodes in infected mice were markedly enlarged compared to controls (P < 0.05). Both CD4+ and CD8+ T cell populations increased in spleens of infected mice while the B cell population increased in mesenteric lymph nodes from infected mice. No significant proliferation was observed when pooled lymphocytes from infected mice were exposed to C. parvum antigens in vitro. Addition of recombinant mouse IFN-gamma did not restore antigen responsiveness. While lymphoproliferative responses to specific antigen were not significant in the short period following infection, this mouse model provides unique features to study the characteristics of acute infection and the immune response against C. parvum.

L-selectin and beta7 integrin synergistically mediate lymphocyte migration to mesenteric lymph nodes

Mesenteric lymph nodes (MLN) drain the gut where nutritive antigens and pathogens are encountered by lymphocytes of the gut-associated lymphoid tissue. We sought to determine how lymphocytes enter the MLN by studying mice double deficient for beta7 integrins and L-selectin. beta7/L-selectin double-deficient lymphocytes did not migrate into MLN. Most importantly, MLN formation was drastically impaired in beta7/L-selectin double-deficient mice. Lymphocyte numbers in MLN from beta7/L-selectin double-deficient mice were tenfold reduced compared to control mice. A high percentage of the few lymphocytes still detected in MLN from beta7/L-selectin double-deficient mice were CD44hi CD18hi, suggesting alternate migration pathways independent of L-selectin and beta7 integrin for these cells. We conclude that the combination of both molecules, L-selectin and beta7 integrin, is indispensable for MLN formation and that these molecules may mediate lymphocyte migration to MLN in a sequential and synergistical manner.

Immunoglobulin A supplementation abrogates bacterial translocation and preserves the architecture of the intestinal epithelium

BACKGROUND

Breast milk has been shown to prevent gut-origin infections in neonates through undefined mechanisms. Putative protective factors in breast milk include immunoglobulin (Ig)A, IgG, and lactoferrin. We examined their role in bacterial translocation in neonatal rabbits.

METHODS

IgA, IgG, and lactoferrin were isolated from rabbit breast milk through gel filtration and ion-exchange chromatography. Neonates were randomized to receive breast milk, formula alone, or formula supplemented with IgA, IgG, or lactoferrin. Quantitative cultures were performed on day 7 for bacterial translocation. Hematoxylin-eosin-stained sections of distal ileum were examined by light microscopy. Transmucosal bacterial passage was determined in vitro, and the ileal mucosal membranes were examined by confocal microscopy.

RESULTS

IgA supplementation abrogated bacterial translocation. IgG and lactoferrin had no significant effect. Neonates that received IgA or breast milk gained more weight than those in the other groups. IgA reduced transmucosal bacterial passage in vitro. In contrast to the normal-appearing distal ileum of neonates fed breast milk, intestinal epithelium from neonates that received formula or formula with IgG or IgA demonstrated prominent vacuoles by light microscopy. Those fed formula alone or formula with lactoferrin had slightly shortened villi.

CONCLUSIONS

IgA supplementation prevents bacterial translocation by enhancing gut mucosal barrier function.

In vivo regulation of PECAM-1 activity during acute endothelial dysfunction in the rat mesenteric microvasculature

The relationship between acute endothelial dysfunction and the extravasation of leukocytes was studied in vivo with intravital microscopy of the rat mesenteric microvasculature. Acute endothelial dysfunction of the rat mesenteric microvasculature was induced in vivo by superfusing the mesentery for 90 min with one of three different stimulating agents: NG-nitro-L-arginine methyl ester (L-NAME, 50 microM), thrombin (0.5 U/mL), or hydrogen peroxide (H2O2, 50 microM). All three agents induced a similar increase in leukocyte rolling and adherence, which was significantly greater than that observed in control rats superfused with Krebs-Henseleit solution (P < 0.01). Transendothelial migration of leukocytes into the perivascular space was also increased by superfusion with L-NAME, thrombin, or H2O2. However, there was a greater increase in the number of migrated leukocytes in the rat mesentery after L-NAME and H2O2 superfusion than that observed during thrombin superfusion. In vivo infusion of a neutralizing antibody against platelet-endothelial cell adhesion molecule-1 (PECAM-1) specifically inhibited L-NAME-induced and H2O2-induced migration of leukocytes but did not prevent extravasation of leukocytes induced by thrombin. In rat mesenteries superfused with the three different stimuli, immunohistochemical analysis of endothelial cell adhesion molecules expressed on the microvascular endothelium revealed a significant increase of ICAM-1, but not PECAM-1, endothelial cell surface expression (P < 0.01 and P > 0.05 vs. control rats, respectively). Our data confirm a key role for PECAM-1 acutely in leukocyte extravasation in vivo and indicate that the involvement of constitutively expressed PECAM-1 in leukocyte transendothelial migration is preferentially correlated to oxidative stress-related stimuli in the microvascular endothelium.

Human and nonhuman primate lymphocytes engrafted into SCID mice reside in unique mesenteric lymphoid structures

The present study compares the location and phenotype of B lineage lymphocytes in tissues from SCID mice engrafted with PBMC of human, chimpanzee, and pig-tailed macaque origin. In mice repopulated with both human and nonhuman primate lymphocytes, plasma cells were found in the peritoneal cavity in vascularized structures located in the mesentery near the pancreas, intestines, and spleen. The predominant isotype of the plasma cells was IgG; IgM and IgA cells were also present. Kappa and lambda light chains were expressed by 62% and 38% of the Ig-containing cells, respectively. J chain expression occurred in most cells irrespective of the Ig isotype. In the SCID mice engrafted with human lymphocytes, a few IgM-containing cells were found in the spleen; plasma cells were not found in other tissues, including the intestine. The aggregation of plasma cells did not appear to be a result of infection with EBV. T cells were rarely found in the lymphoid aggregates but were recovered from the spleen and peritoneal lavage. Human Ig levels in the serum of engrafted mice reflected the isotype distribution of the cells with IgG > IgM > or = IgA.

A role for tumor necrosis factor receptor type 1 in gut-associated lymphoid tissue development: genetic evidence of synergism with lymphotoxin beta

Lymphotoxin alpha (LTalpha) signals via tumor necrosis factor receptors (TNFRs) as a homotrimer and via lymphotoxin beta receptor (LTbetaR) as a heterotrimeric LTalpha1beta2 complex. LTalpha-deficient mice lack all lymph nodes (LNs) and Peyer's patches (PPs), and yet LTbeta-deficient mice and TNFR-deficient mice have cervical and mesenteric LN. We now show that mice made deficient in both LTbeta and TNFR type 1 (TNFR1) lack all LNs, revealing redundancy or synergism between TNFR1 and LTbeta, acting presumably via LTbetaR. A complete lack of only PPs in mice heterozygous for both ltalpha and ltbeta, but not ltalpha or ltbeta alone, suggests a similar two-ligand phenomenon in PP development and may explain the incomplete lack of PPs seen in tnfr1-/- mice.

beta1 integrins are critically involved in neutrophil locomotion in extravascular tissue In vivo

Recruitment of leukocytes from blood to tissue in inflammation requires the function of specific cell surface adhesion molecules. The objective of this study was to identify adhesion molecules that are involved in polymorphonuclear leukocyte (PMN) locomotion in extravascular tissue in vivo. Extravasation and interstitial tissue migration of PMNs was induced in the rat mesentery by chemotactic stimulation with platelet-activating factor (PAF; 10(-7) M). Intravital time-lapse videomicroscopy was used to analyze migration velocity of the activated PMNs, and the modulatory influence on locomotion of locally administered antibodies or peptides recognizing various integrin molecules was examined. Immunofluorescence flow cytometry revealed increased expression of alpha4, beta1, and beta2 integrins on extravasated PMNs compared with blood PMNs. Median migration velocity in response to PAF stimulation was 15.5 +/- 4.5 micron/min (mean +/- SD). Marked reduction (67 +/- 7%) in motility was observed after treatment with mAb blocking beta1 integrin function (VLA integrins), whereas there was little, although significant, reduction (22 +/- 13%) with beta2 integrin mAb. Antibodies or integrin-binding peptides recognizing alpha4beta1, alpha5beta1, or alphavbeta3 were ineffective in modulating migration velocity. Our data demonstrate that cell surface expression of beta1 integrins, although limited on blood PMNs, is induced in extravasated PMNs, and that members of the beta1 integrin family other than alpha4beta1 and alpha5beta1 are critically involved in the chemokinetic movement of PMNs in rat extravascular tissue in vivo.

[Structure of the rat lymphoid organs after prenatal exposure to indomethacin during antigenic stimulation]

Primary immune response of thymus and mesenteric lymph nodes to prenatal action of indomethacin was studied in one month rats. Indexes of cell reactions in the experimental rat thymus were found to coincide with control during all phases although blast transformation intensity was slightly reduced. In mesenteric lymph nodes primary immune response was suppressed which was connected with lymphocyte functional insufficiency. This is manifested through less intensive intercellular cooperation in the first phase, suppression of blast transformation in B lymphocytes in the second and decrease of functional activity of the node B zones in the third ones.

Impairment in connective tissue mast cells degranulation in spontaneously hypertensive rats: stimulus dependent resistance

1. Microvascular permeability in the mesentery and consequent leakage of protein into the peritoneum of spontaneously hypertensive rats (SHR) and normotensive rats (NTR) was measured in vivo by the extravasation of Evans blue dye. 2. In sensitized NTR, challenge with antigen produced extensive increases in dye extravasation in the mesentery and in peritoneal lavage fluid within 10 min. 3. In sensitized SHR there was no increase in the permeability of the mesentery and a very weak increase in dye extravasation in the peritoneal cavity following challenge. 4. The glucocorticoid antagonist RU38486 did not change the permeability response induced by antigen in sensitized NTR and SHR. 5. However, compound 48/80 was equally effective in either NTR or SHR in causing increased vasopermeability. 6. Mesenteric mast cells in the NTR were degranulated after immunological challenge, whereas those in the SHR were resistant, as measured histologically. 7. Similarly, challenge ex vivo of mesentery from sensitized NTR induced contraction of guinea-pig ileum in co-incubation experiments, whereas SHR mesentery was unresponsive. 8. Plasma levels of antigen-specific IgE and IgG2a in sensitized NTR and SHR were identical. 9. Immune serum from SHR was unable to induce a passive cutaneous anaphylaxis (PCA) reaction in the skin of NTR and SHR did not develop a PCA reaction upon passive sensitization with NTR immune serum. 10. We conclude that the mast cells of SHR are resistant to degranulation following immunological challenge, although the relevant antibodies are present.

Changes in lymphocyte subsets in the intestine and mesenteric lymph nodes in caprine paratuberculosis

Changes in the number and distribution of lymphocyte subsets were investigated in the intestinal mucosa and mesenteric lymph nodes of three goats with natural paratuberculosis, comparisons being made with a single uninfected control animal. Lesions in the naturally infected goats varied from small granulomata with scarce epithelioid or multinucleated giant cells, containing few or no bacilli, in the intestine (tuberculoid type) to an extensive, diffuse epithelioid cell infiltrate containing numerous bacilli in the gut and mesenteric lymph nodes (lepromatous type). The number and distribution of lymphocyte subsets in the control were consistent with data reported from other non-infected goats. However, in the goats with paratuberculosis, significant changes were observed in the number and distribution of CD4+ and CD8+ T lymphocytes, the changes being related to the severity of the lesions. In the intestinal mucosa of the goat with tuberculoid lesions no significant changes were observed, but in the cortical area of mesenteric lymph nodes the number of CD4+ T lymphocytes decreased and the number of CD8+ T lymphocytes increased. In the two goats with lepromatous lesions, there was a decrease in the CD4+ T subpopulation and an increase of CD8+ T lymphocytes in the lamina propria of the intestine and particularly in the cortical area of the mesenteric lymph nodes, the CD4:CD8 ratio (< 1) being the opposite of that observed in healthy goats. Because of the small numbers of animals, further studies including additional animals are needed to confirm these preliminary results, which suggest that the progression of paratuberculous lesions may be due to an ineffective host immune response attributable to the CD8+ T lymphocyte subset that "downregulates" the activity of the CD4+ T lymphocytes required for macrophage activation.

Gut bacterial translocation during total parenteral nutrition in experimental rats and its countermeasure

BACKGROUND

The use of total parenteral nutrition (TPN) is commonly associated with mucosal lining of the intestinal tract, causing degenerative changes within the gut-associated lymphoid tissue (GALT). These phenomena are probably caused by the translocation of indigenous intestinal bacteria into other organs and tissues where they induce infections.

METHODS

Using TPN model rats, this paper looks at the result of the investigation of the action of PSK (proteoglycan), a biological response modifier, which appears to suppress bacterial translocation and maintain local immunity activity.

RESULTS

Culture of mesenteric lymph nodes obtained post-TPN demonstrate a bacterial rate as high as 60%. Immunohistochemical examination indicates a reduction in the number of plasma cells and a decrease in S-IgA production and secretion. A similar reduction in S-IgA within bile and portal venous blood was also confirmed. Continuous oral administration of PSK in a daily dose of 1,000 mg/kg had a protective effect against the degeneration of GALT. A staining in immunocytes of Peyer's patches using immunohistochemical study was performed after administration of PSK and revealed constant levels of MHC-I, MHC-II, T helper cells, and interleukin-2 producing cells, supporting the protective role of PSK against degeneration of GALT with a subsequent reduction in bacterial translocation.

CONCLUSIONS

Proteoglycan can restore the impaired local immunity in the intestinal tract to normal levels and suppression of the bacterial translocation to provide an important function for patients receiving TPN treatment.

Immunosurveillance modelled in vitro: naive and memory T cells spontaneously migrate across unstimulated microvascular endothelium

As a model for T cell immigration into non-lymphoid tissue we set up an in vitro assay that would allow us to investigate the phenotype of T lymphocytes from peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN) or peripheral blood (PBL) of mice, which were able to spontaneously migrate across unstimulated microvascular endothelium. The transendothelial migrating T cell population was enriched for T lymphocytes expressing a "recently activated/memory' phenotype: LFA-1/CD44/ICAM-1high, but also contained CD45RBhigh and LFA-1low T cells, which in the case of MLN T cells were phenotyped as CD4+ and thus characterized as naive T cells. Transmigrated T cells could be further distinguished from their original populations and from each other by their distinct but heterogeneous expression patterns for L-selectin, alpha 4 beta 7-integrin and PECAM-1. This observation suggests the presence of phenotypically different migratory T cells among MLN, PLN and PBL. Additional studies provided evidence that the capacity to migrate across unstimulated microvascular endothelium was a characteristic of a T cell population that could phenotypically be differentiated from activated T cells. The endothelial cells were found to play an active role in selecting the traversing T cell population, as they controlled the number and phenotype of spontaneously transmigrating T cells. Our studies suggest that the capacity to transmigrate across unstimulated microvascular endothelium and hence to immigrate into non-lymphoid tissue is owned by a phenotypically heterogeneous T cell population, which is enriched for memory T cells but not devoid of naive T cells.

Development of antibody-secreting cells and antigen-specific T cells in cervical lymph nodes after intranasal immunization

Intranasal (i.n.) immunization with bacterial protein antigens coupled to cholera toxin B subunit (CTB) effectively induces mucosal, especially salivary immunoglobulin A (IgA), and nonmucosal antibody responses in mice. To examine the regional distribution of antigen-specific B and T cells after i.n. immunization, antibody-secreting cells and antigen-responsive T cells in cervical lymph nodes (CLN) were compared with those found after intraoral or subcutaneous (in the neck) administration of the same antigen and with T cells found in mesenteric lymph nodes (MLN) and spleen after intragastric immunization. The i.n. immunization induced predominantly IgA antibody-secreting cells in salivary glands and IgA and IgG antibody-secreting cells in the superficial and central CLN; these responses were quantitatively enhanced if the antigen was coupled to CTB. Intraoral immunization also induced IgA and IgG antibody-secreting cells in the superficial and central CLN, but only if intact cholera toxin was included as an adjuvant. In contrast, subcutaneous (neck) immunization induced IgG antibody-secreting cells mainly in the draining facial lymph nodes. CLN cell populations resembled those of MLN, except that CLN lymphocytes had higher proportions of T cells and lower proportions of B cells and a slightly higher CD4+/CD8+ ratio among T cells than the MLN lymphocytes did. T cells that proliferated in response to antigen in vitro were found especially in central CLN 2 days after i.n. immunization and persisted for up to 6 months, whereas after intragastric immunization, responsive T cells were not found in the MLN for up to 14 days. After culture with antigen in vitro, T cells from the superficial CLN of i.n. immunized mice secreted both gamma interferon and interleukin-4. Therefore, after i.n. immunization, superficial and central CLN represent sites of regional lymphocyte development, and the central CLN in particular appear to be sites where memory T cells persist.

Microbial colonization influences composition and T-cell receptor V beta repertoire of intraepithelial lymphocytes in rat intestine

Studies in mice have shown that the composition of intestinal intraepithelial lymphocytes (IEL) may be markedly altered by gut microbial colonization. Such modulation was studied in a rat model by the use of germ-free and conventionalized animals from which IEL from the small intestine were isolated and analysed by flow cytometry. Conventionalization caused expansion as well as phenotypic alterations of T-cell receptor (TCR) alpha/beta + IEL in that the proportions of CD4+ and CD8 alpha beta + TCR alpha/beta + cells were increased, while the double negative (CD4- CD8-) fraction was reduced. microbial colonization also influenced the TCR V beta repertoire of CD8+ IEL in that the proportions of V beta 8.2+ and V beta 10+ cells were increased, whereas V beta 8.5+ and V beta 16+ cells were relatively decreased. Moreover, conventionalization influenced the levels of TCR cell surface expression in the same V beta subsets. Three-colour flow-cytometric analysis demonstrated that skewing of the V beta repertoire was most pronounced in the CD8 alpha alpha + subset, although the numerical increase of IEL mainly included the CD8 alpha beta + subset. In contrast to IEL, the TCR V beta repertoire in mesenteric lymph nodes was unchanged after intestinal colonization. These results confirm that TCR alpha/beta + IEL subpopulations respond dynamically to the microbial gut flora and suggest that their V beta repertoire can be shaped by luminal microbial antigens.

Apoptosis and T-cell depletion during feline infectious peritonitis

Cats that have succumbed to feline infectious peritonitis, an immune-mediated disease caused by variants of feline coronaviruses, show apoptosis and T-cell depletion in their lymphoid organs. The ascitic fluid that develops in the course of the condition causes apoptosis in vitro but only in activated T cells. Since feline infectious peritonitis virus does not infect T cells, and viral proteins did not inhibit T-cell proliferation, we postulate that soluble mediators released during the infection cause apoptosis and T-cell depletion.

Evidence for the presence of G-proteins, adenylyl cyclase and phospholipase C activities in lymphatic smooth muscle cell membranes

In plasma membranes derived from bovine mesenteric lymphatic smooth muscle cells, guanine nucleotide and forskolin stimulated adenylyl cyclase (AC) activity in a concentration-dependent manner, indicative of the presence of the stimulatory G-protein Gs linked to AC. There was no significant enzyme inhibition by low concentrations of guanine nucleotide and no effect on basal or guanine nucleotide-stimulated activity following pertussis toxin treatment of cells, suggesting the absence of Gi linked to inhibition of AC. Furthermore, there was no effect of adrenaline, isoprenaline or clonidine on basal or forskolin-stimulated activities, nor was there any specific binding of the beta-adrenoceptor ligand [125I]cyanopindolol to membranes, suggesting that catecholamine receptors do not modulate AC activity in these membranes. Pertussis toxin-mediated ADP ribosylation of membrane proteins and Western immunoblotting analysis revealed the presence of G-protein subunits G alpha i2, G alpha q, and G beta 1. In experiments designed to identify a possible effector enzyme for these G-proteins, membranes were screened with a range of antibodies raised against phospholipase C (PLC) beta, gamma and delta isozymes. Though no evidence was obtained by Western blotting for any of these proteins, PLC activity was concentration-dependently stimulated by Ca2+, but not by AIF4-, GTP[S], or purified G beta gamma subunits. Finally, no specific binding to membranes of the alpha 1-adrenoceptor ligand [3H]prazosin or the alpha 2-adrenoceptor ligand [3H]yohimbine was obtained. In conclusion, this study provides evidence for a Gs-dependent stimulation of AC, and for the presence of Gi2 and Gq/11, which do not appear to regulate a PLC activity also identified in lymphatic smooth muscle cell membranes. Furthermore, neither AC nor PLC appear to be associated with catecholamine receptors.

Effect of unsaturated fatty acids and antioxidants on immunoglobulin production by mesenteric lymph node lymphocytes of Sprague-Dawley rats

The effect of UFA on Ig production by rat MLN lymphocytes was examined to clarify their influence on allergic reactions. A 4-h treatment at 1 mM inhibited the production of IgA, IgG, and IgM by the lymphocytes, but stimulated IgE production. The IgE production-stimulating activity became stronger with increasing number of carbon atoms and/or double bonds. However, no saturated fatty acid with carbon numbers from 12 to 18 affected IgE production by the lymphocytes. Hydrogen peroxide exerted Ig production-regulating activity similar to that of UFA, suggesting that the effect of UFA is at least partly due to oxidation products. Thus, the effect of antioxidants on the Ig production-regulating activity of arachidonic acid was examined. alpha-Tocopherol and BHT annulled the stimulation of IgE production by arachidonic acid, but ascorbic acid was not effective. The IgE production-enhancing activity of UFA was closely related to their oxidation rate in culture medium. These results suggest that UFA enhance the allergic reaction through the stimulation of IgE production and the inhibition of IgA production, and that hydrophobic antioxidants are partially effective to annul the adverse effect of UFA.

The involvement of transforming growth factor beta in the impaired antitumor T-cell response at the gut-associated lymphoid tissue (GALT)

We studied the antitumor immune response in gut-associated lymphoid tissue (GALT), which is the tolerance-inducing site for numerous dietary antigens. The mice inoculated with colon 26 carcinoma (C-26) into the subserosal space of the cecum (i.c.) showed a more rapid tumor growth than did the mice inoculated s.c. with C-26 into the flank. In addition, the serum of the i.c. C-26-inoculated mice showed a more potent suppressive activity, and their plasma contained a higher level of transforming growth factor than the s.c. C-26-inoculated mice. We also evaluated the tumor-specific T-cell response in the GALT by utilizing B7-transfected P815 mastocytoma (B7/P815). The rejection of i.c. inoculated B7/P815 was delayed compared to that of the s.c. inoculated B7/P815. The draining axillary lymph node (LN) cells of the s.c. B7/P815-inoculated mice exhibited a CD4+ T-cell-dependent proliferative response to in vitro restimulation, whereas the draining mesenteric LN cells of the i.c. B7/P815-inoculated mice exhibited no apparent response even with the addition of interleukin 2. However, such draining mesenteric LN cells did produce higher levels of interleukin 2 and transforming growth factor beta than the draining axillary LN without any stimulation, and their production of such cytokines depend on the CD4+ and CD8+ cells, respectively. Collectively, our results suggest the possibility that the impaired antitumor T-cell response in the GALT may be attributed to "bystander suppression" by TGF-beta-producing CD8+ T cells.

The impact of surgical technique on the development of graft versus host disease in a rat small intestinal transplant model

The small intestine and its mesentery contain a large amount of lymphoid tissue that can mediate graft-versus-host disease (GVHD) in small intestinal transplant recipients. To assess the impact of surgical technique and the retention of the recipient's small intestine on GVHD intensity, 12 adult Lewis rats received heterotopic small bowel transplants and 12 received orthotopic small bowel transplants from Brown Norway donors. Twelve Lewis to Lewis heterotopic small-bowel-transplanted animals served as the control group. All recipients were given cyclosporine (10 mg/kg/alternate days) subcutaneously. The parameters followed were: weight gain and feed intake; clinical signs of GVHD; relative spleen weight; popliteal lymph node enlargement assay; and histological evaluation of spleen, liver, skin, native intestine, and transplanted intestine. According to the clinical scoring system, heterotopically transplanted animals were found to have a more severe GVHD than the orthotopic group. There were statistically significant differences between the relative spleen weights of the heterotopic transplant group and the control group (P = 0.001, 0.004, and 0.007 on days 7, 14, and 21, respectively) and between the heterotopic and orthotopic groups at 7 days (P = 0.037). Lymph node enlargement assays were statistically different between heterotopic and orthotopic groups (P = 0.019, 0.020, and 0.007 on days 7, 14, and 21, respectively). Histological evaluation of skin biopsy specimens also demonstrated that GVHD was indeed more severe in the heterotopic transplanted group when compared with orthotopically transplanted animals. These findings confirm that retention of the native small intestine in the heterotopic intestinal transplant model significantly increases the severity of GVHD following transplantation.

5-Hydroxytryptamine-immunoreactive nerve fibers in the rat and porcine prevertebral sympathetic ganglia: effect of precursor loading and relation to catecholaminergic neurons

Localization of 5-hydroxytryptamine immunoreactivity was studied in the rat coeliac-superior mesenteric ganglion complex and in the porcine superior and inferior mesenteric ganglia by the indirect immunofluorescence technique. In normal rats, only 5-hydroxytryptamine immunoreactive SIF cells were seen in the coeliac-superior mesenteric ganglion complex. In the rats, pretreated with a 5-hydroxytryptamine precursor, L-tryptophan, and with a monoamine oxidase inhibitor, nialamide, a large number of 5-hydroxytryptamine-immunoreactive nerve fiber terminals were detected. In normal porcine superior and inferior mesenteric ganglia, intense 5-hydroxytryptamine immunoreactivity was found in numerous nerve fibers which were located around tyrosine hydroxylase-immunoreactive principal neurons. The origin and function of these fibers are discussed.

Efficacy of oral vaccination against the murine intestinal parasite Trichuris muris is dependent upon host genetics

Oral vaccinations with Trichuris muris adult worm homogenate antigen with cholera toxin as the adjuvant were successful in both high-responder BALB/c and low-responder C57BL/10 mice, resulting in high levels of protection against subsequent infection, but were ineffective in the low-responder B10.BR mice. Subcutaneous vaccination with antigen in Freund's complete adjuvant resulted in protection of all of these strains but was most effective in high-responder BALB/c and least effective in B10.BR mice. Oral vaccination resulted in a T. muris-specific intestinal immunoglobulin A response only in the two protected strains. High levels of serum immunoglobulin G1 antibody were induced by Freund's complete adjuvant vaccination in all cases. A relationship between vaccine efficacy, expulsion phenotype, and induced T-helper subset-associated cytokines (interleukin-5 and gamma interferon) was noted. It was concluded that effective vaccination against T. muris requires the induction of Th2 responses and that this can be achieved by both oral and parenteral administration of antigens.

Rat intestinal dendritic cells: immunostimulatory potency and phenotypic characterization

Dendritic cells (DC) acquire antigens in peripheral tissues, transport them to lymph nodes and present peptides to T cells. DC are particularly good activators of resting T cells. Murine Langerhans' cells (LC) are efficient at endocytosing and processing antigens but are very weak immunostimulators. In culture LC lose the ability to process antigen and become potent immunostimulators. Other peripheral DC are not well characterized and it is not known if they are similarly weak immunostimulators. We isolated DC from rat Peyer's patches (PP) and lamina propria (LP) of the small intestine, from intestinal lymph (LDC) and mesenteric lymph nodes, and examined their ability to stimulate an allogeneic mixed leucocyte reaction (MLR). Freshly isolated LP DC and PP DC could stimulate a moderate MLR but fresh LDC were significantly more potent. After overnight culture, LDC did not change their potency but DC from LP and PP became as potent as LDC. In contrast, fresh lymph node DC stimulated a MLR or oxidative mitogenesis as efficiently as LDC. These results show that the weak immunostimulation of murine LC is not characteristic of all peripheral DC. We compared the phenotypes of DC from different sites before and after culture. Different populations of DC show marked phenotypic heterogeneity in the expression of surface markers, particularly Thy-1, CD2 and the iC3b receptor. PP and LP DC were similar to MLN DC in their expression of markers, but differed from LDC. After culture there were marked changes in DC surface marker expression and the differences between the populations were reduced. These observations suggest that the heterogeneity observed in fresh populations does not signify different stages of maturation but may represent activation.

Biliary secretion of antibody to dextran following oral immunization with dextran B512

Anti-dextran in bile was induced to high levels by oral immunization with dextran B512. IgM anti-dextran were dominant in serum, whereas IgG anti-dextran was dominant in bile. The binding properties of these IgM and IgG antibodies were different, as determined by ELISA with several dextrans. Splenocytes produced equal amounts of IgG and IgM antidextran but cells from mesenteric lymph nodes (MLN) and Peyer's patches produced mainly IgG anti-dextran. Differences were observed among different strains of mice in their ability to produce anti-dextran in serum and bile upon immunization with dextran. BALB/c mice, which are intermediate responders in terms of their serum antibody levels, produced high levels of anti-dextran in bile. C3H/He and C57BL/6, which are high responders in terms of serum antibody levels, had intermediate responses in bile. DBA/2, which are low responders in terms of serum antibody levels, showed low responses in bile. The results provide further evidence of the existence of anti-dextran producing cells. These results indicate that B cells in systemic and mucosal-associated lymphoid tissues from BALB/c, C3H/He, C57BL/6 and DBA/2 mice respond differently to oral immunization with dextran B512.

In vivo induction of interleukin-12 mRNA expression after oral immunization with Salmonella dublin or the B subunit of Escherichia coli heat-labile enterotoxin

Mice orally immunized with Salmonella dublin EL23, a nonreverting, aromatic-dependent, histidine-requiring mutant transformed with a plasmid which carries a gene that codes for production of the B subunit of the heat-labile toxin (LT-B) of enterotoxigenic Escherichia coli, or with purified LT-B alone were compared for their ability to initiate expression of interleukin-12 (IL-12) mRNAs at mucosal sites. At 6 or 20 h following oral immunization, the Peyer's patches and mesenteric lymph nodes were removed, and polyadenylated mRNA was prepared from each tissue. Constitutive expression of an mRNA encoding the p35 subunit of IL-12 was observed in control as well as immunized mice. Conversely, expression of an mRNA encoding the p40 subunit of IL-12 was not detected in control animals but was dramatically upregulated in immunized mice. By using semiquantitative reverse transcription-PCR (RT-PCR) followed by competitive RT-PCR, differences in the magnitude of IL-12 p40 mRNA expression were quantified. Six hours after oral immunization with the Salmonella construct, mice had 12.1- and 8.4-fold increases in expression of IL-12 p40 mRNA in the Peyer's patches and mesenteric lymph nodes, respectively, compared with control mice receiving only saline. By 20 h, the pattern of increased mRNA expression was reversed, showing 2.5- and 17.6-fold increases in the Peyer's patches and mesenteric lymph nodes, respectively. Oral immunization with LT-B alone also stimulated IL-12 p40 mRNA expression, but to a lesser extent. The constitutive expression of IL-12 p35 mRNA at these mucosal sites coupled with a rapid and dramatic induction of IL-12 p40 mRNA following immunization with wild-type or attenuated strains of S. dublin is consistent with other investigations which support a role for IL-12 in modulating cell-mediated immune responses against intracellular pathogens.

Lipopolysaccharide-induced apoptosis in swine lymphocytes in vivo

The in vivo effects of bacterial lipopolysaccharide (LPS) on the immune systems of piglets were investigated. Intravenous injection of 0.5 mg of LPS per kilogram of body weight induced apoptosis, which was characterized by nuclear chromatin condensation and fragmentation and a ladder formation of nucleosomal DNA in lymphocytes both in the cortex of the thymus and in the germinal centers and paracortical areas of mesenteric lymph nodes at 24 h postinjection. The levels of endotoxin, tumor necrosis factor alpha, and cortisol in serum increased, generally according to the dose of LPS. These findings suggest that LPS can induce in vivo apoptosis of lymphocytes in piglets and support the notion that cytokine and endocrine responses may play an important role in LPS-induced apoptosis in the immune system.

Modulation of cytokine secretion by mesenteric lymph node cells from vitamin A-deficient mice during Hymenolepis nana infection

The influence of vitamin A deficiency on the development of cellular immune responses was examined using vitamin A-deficient mice (A mice)/Hymenolepis nana system. Mesenteric lymph node cells (MLNC) prepared from both normal BALB/c mice and A mice during H. nana infection proliferated extensively when cultured with soluble egg antigen of H. nana as assessed by 3H-thymidine incorporation. MLNC from normal mice secreted significantly more IL-2 and significantly less IFN-gamma than A mice when the cells were cultured in the presence of soluble egg antigen.

Regional differences in lymphocyte function following resuscitated hemorrhagic shock

Although it is well known that hemorrhagic shock causes immunosuppression, there have been few attempts to define these changes in the various immune compartments. Accordingly, male rats were bled into severe hemorrhagic shock for 60 minutes (mean arterial pressure 35 +/- 5 mm Hg). Twenty-four hours following resuscitation, splenic, mesenteric, and peripheral lymphocytes were harvested for cell population analysis and mitogen stimulation assays. Cell marker analysis revealed no changes in B-cell or T-cell subpopulations in any immune compartment after shock. The splenic and peripheral lymphocytes showed marked depression of mitogen-induced stimulation after shock. In contrast, mesenteric lymphocyte responses to both T-cell and B-cell mitogens were not depressed after shock. Regional variability in mitogen responses after shock occur without change in B-cell or T-cell subpopulations in any immune compartment tested. The mechanism or mechanisms involved warrant further investigation.

Regulatory T cell clones induced by oral tolerance: suppression of autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a cell-mediated autoimmune disease that serves as an animal model for multiple sclerosis. Oral administration of myelin basic protein (MBP) suppresses EAE by inducing peripheral tolerance. T cell clones were isolated from the mesenteric lymph nodes of SJL mice that had been orally tolerized to MBP. These clones were CD4+ and were structurally identical to T helper cell type 1 (TH1) encephalitogenic CD4+ clones in T cell receptor usage, major histocompatibility complex restriction, and epitope recognition. However, they produced transforming growth factor-beta with various amounts of interleukin-4 and interleukin-10 and suppressed EAE induced with either MBP or proteolipid protein. Thus, mucosally derived TH2-like clones induced by oral antigen can actively regulate immune responses in vivo and may represent a different subset of T cells.

T lymphocytes in host defense against bacterial translocation from the gastrointestinal tract

Flow cytofluorometric analyses of lymphocytes harvested from the mesenteric lymph node (MLN), mucosal epithelium, and lamina propria of C57BL/6 mice demonstrate that expression of alpha/beta or gamma/delta T-cell receptors (TCR) and CD4 or CD8 molecules by T lymphocytes in the intestinal immune system varies depending upon their anatomic location. The MLN contained equivalent numbers of CD4+ and CD8+ T cells, the vast majority of which were alpha/beta TCR positive (alpha/beta TCR+). The lamina propria T cells were predominantly CD4+ and alpha/beta TCR+, while the intestinal intraepithelial lymphocytes consisted of equivalent numbers of alpha/beta and gamma/delta T cells, the majority of which were CD8+. There were no significant changes in these T-cell phenotypic profiles when the mice were antibiotic decontaminated or monoassociated with Escherichia coli. Mice were depleted of CD4+ T cells and/or CD8+ T cells in vivo by intraperitoneal injections of monoclonal antibody GK 1.5 (rat anti-mouse CD4) and/or monoclonal antibody 2.43 (rat anti-mouse CD8). T-cell depletion was confirmed in the MLN, lamina propria, and the intestinal epithelium by flow cytometry. E. coli C25 translocation from the gastrointestinal (GI) tract to the MLN was significantly increased in mice depleted of CD4+ T cells, CD8+ T cells, or both. T-cell-deficient athymic beige/nude mice also exhibited greater levels of E. coli C25 translocation to the MLN than beige/het euthymic littermates. Salmonella typhimurium translocation also was increased following CD4+ and CD8+ T-cell depletion in mice monoassociated with S. typhimurium. Depletion of CD4+ and/or CD8+ T cells also increased the translocation to the MLN of certain indigenous GI flora bacteria. These results confirm that T-cell-mediated immunity is involved in the host defense against bacterial translocation from the GI tract.

Characterization of horse (Equus caballus) T-cell receptor beta chain genes

Genes encoding the horse (Equus caballus) T-cell receptor beta chain (TCRB) were cloned and characterized. Of 33 cDNA clones isolated from the mesenteric lymph node, 30 had functionally rearranged gene segments, and three contained germline sequences. Sixteen unique variable segments (TCRBV), 14 joining genes (TCRBJ), and two constant region genes (TCRBC) were identified. Horse TCRBV were grouped into nine families based on similarity to human sequences. TCRBV2 and TCRBV12 were the most commonly represented horse families. Analysis of predicted protein structure revealed the presence of conserved regions similar to those seen in TCRB of other species. A decanucleotide promoter sequence homologous to those found in humans and mice was located in the 5' untranslated region of one horse gene. Germline sequences included the 5' region of the TCRBD2 gene with flanking heptamer/nonamer recombination signals and portions of the TCRBJ2-C2 intron. Southern blot hybridizations demonstrated restriction fragment length polymorphisms at the TCRBC locus among different horse breeds.

The role of interleukin-6 in mucosal IgA antibody responses in vivo

In mice with targeted disruption of the gene that encodes interleukin-6 (IL-6), greatly reduced numbers of immunoglobulin A (IgA)-producing cells were observed at mucosae and grossly deficient local antibody responses were recorded after mucosal challenge with either ovalbumin or vaccinia virus. The IgA response in the lungs was completely restored after intranasal infection with recombinant vaccinia viruses engineered to express IL-6. These findings demonstrate a critical role for IL-6 in vivo in the development of local IgA antibody responses and illustrate the effectiveness of vector-directed cytokine gene therapy.

Elemental diet-induced bacterial translocation and immunosuppression is not reversed by glutamine

Previously, we documented that bacterial translocation occurs in rats fed an elemental liquid diet (4.25% amino acids plus 28% glucose) for 7 days. Since controversy exists over the protective effect of glutamine on diet-induced bacterial translocation, we compared the effect of two elemental diets, one containing 0% and the other 30% of amino acids as glutamine. After 7 days on the test diets or chow (307 kcal/kg/day), the rats were killed and half the animals had their organs cultured for translocating bacteria; immune function was quantitated in the other half by measuring the blood, splenic, and mesenteric lymph node (MLN) blastogenic responses to the T-cell mitogens phytohemagglutinin (PHA) and concanavalin A (ConA). The incidence of bacterial translocation was higher in the rats fed the glutamine (88%) or nonglutamine (75%) elemental diets than in the chow-fed rats (13%) (p < 0.05). Both elemental diets equally reduced the blastogenic response of lymphocytes harvested from all three lymphoid compartments (blood, spleen, MLN) (p < 0.01 vs. chow). The percentage of reduction averaged 30% to 40% when PHA was used as the test mitogen and 50% to 70% when ConA was used. These results indicate that glutamine does not prevent elemental diet-induced bacterial translocation or immune suppression.

Sequence of ovine Ig gamma 2 constant region heavy chain cDNA and molecular modelling of ruminant IgG isotypes

Ovine mesenteric lymph node mRNA was used for PCR amplification of DNA coding for immunoglobulin gamma 1 and gamma 2 heavy chain constant regions. Primers complementary to regions of CH1 conserved between ruminants were used for upstream priming, with downstream priming on the poly-A segment. PCR products of the appropriate length were cloned and gamma positive clones selected with a CH1 conserved-region probe. Of these, gamma 1 clones were positively selected and gamma 2 clones negatively selected with a gamma 1 hinge-specific probe. Ovine gamma 2 cDNA has 93% identity of nucleotides with ovine gamma 1. Both ovine gamma 1 and gamma 2 CH1 domains encoded two consecutive cysteine residues (Cys-127, -128, Kabat numbering), an arrangement which is deduced to form a pair of disulphide bridges, one to the L chain and one as an intra-chain bridge to the uppermost Cys of the hinge, as in rabbit and goat IgG. The majority of the differences between the isotypes occur in the hinge region and an evolutionary pattern for ruminant IgG hinges can now be identified. IgG1 isotypes are typical, with hinges containing the C-terminal Cys-Pro motif, but deletion and replacement of nucleotides (in the ancestral gene) of ruminant gamma 2 has shortened the IgG2 hinge, removing the Cys-Pro motif and the consensus high affinity Fc gamma RI receptor motif at the start of CH2. An N-terminal glycosylation site and the peptide motif for complement C1q binding are present in CH2 of both isotypes. The hinge regions of gamma 1 and gamma 2 and predicted structures for ovine IgG1 and IgG2 have been modelled. Close apposition of Fab and Fc in IgG2 produces steric hindrance at the normally accessible Fab/hinge/Fc interface; the structural differences between the ruminant isotypes form a basis for understanding some of the differences in their effector properties.

The chondroitin sulfate form of invariant chain can enhance stimulation of T cell responses through interaction with CD44

Invariant chain (Ii) is a nonpolymorphic glycoprotein that associates with major histocompatibility complex class II molecules and has been shown to mediate several functions in class II-restricted antigen presentation. A small proportion of Ii is modified by the addition of chondroitin sulfate (Ii-CS), and this form of Ii is associated with class II on the surface of antigen-presenting cells. In this report we show that expression of Ii-CS dramatically enhanced the ability of class II-positive EL4 transfectants to stimulate class II-dependent allogeneic and mitogenic T cell responses. Antibody blocking studies and the ability of CD44 to bind directly to Ii-CS suggest that Ii-CS can function as an accessory molecule during T cell responses through interactions with CD44.

Comparison of potentiality to induce graft-versus-host reaction with small bowel, pancreas/spleen, and liver transplantation in the rat

Although small bowel transplantation (SBT), or pancreas-spleen transplantation (PST) often lead to lethal graft-versus-host reaction (GVHR) in experimental animals, fatal GVHR is rare after clinical liver transplantation. This study describes a modified model of SBT and PST in the rat using cuff techniques applied to the renal artery and vein of the recipient. The ability of LEW (RT1(1)) or BN (RT1n) lymphocytes accompanying intestinal, splenic, or hepatic grafts to induce lethal GVHR in (LEW x BN) F1 hybrid recipients was compared. SBT and PST experiments showed that lethal GVHR always occurred in LEW-into-F1 combination, but was much less frequent in BN-into-F1 SBT. In mixed lymphocyte reaction (MLR), LEW mesenteric or splenic T cells showed significantly higher proliferative responses against BN stimulators than did BN mesenteric or splenic T cells against LEW. Adoptive cell transfer experiments using mesenteric or splenic cells also showed that LEW cells were higher responders than BN. In contrast with SBT and PST results, a lethal GVHR was not induced after liver or pancreas grafting alone in either parent-to-F1 combination. In MLR, hepatic T cells from either parent failed to elicit a proliferative response against allostimulators. These results indicate that the occurrence of lethal GVHR is dependent upon the reactivity of parental lymphocytes against allo-antigenicity of F1 hybrids and also upon the lymphoid tissue transplanted. The lack of alloreactivity of hepatic T cells accounts for the absence of lethal GVHR after liver grafting.

Oxyradical generation from leukocytes during endotoxin-induced microcirculatory disturbance in rat mesentery--attenuating effect of cetraxate

By using the intravital microscope equipped with digital imaging processor, we investigated the granulocyte-mediated oxidative burst during the endotoxin-induced microvascular derangement in rat mesentery. The leukocyte behavior after the injection of acridine orange was detected by using a silicon-intensified target camera, the erythrocyte velocity was measured by using a high-speed video camera system, and the luminol-dependent photoemission was visualized by an ultrasensitive photon-counting camera in lipopolysaccharide (LPS)-treated microvascular beds. At 60 min after the LPS administration, a significant leakage of FITC-labeled albumin was observed along mesenteric venules under a fluorescence microscopy. The number of sticking leukocytes increased in association with the decrease in erythrocyte velocity after starting the LPS infusion. The luminol-dependent chemiluminescence in microvascular beds gradually increased over that recorded prior to LPS exposure and was fourfold higher 60 min after the start of LPS infusion. The distribution of the photoemission clearly corresponded to the venular endothelium, to which leukocytes adhered. In blood samples taken from the mesenteric vein at 60 min after the LPS administration, a decrease in the number of granulocytes and increases of total and individual chemiluminescence activities were observed. These results suggest that LPS induces oxidative burst from granulocytes on the venular endothelium. Cetraxate, an inhibitor of proteases including plasmin, significantly inhibited the leukocyte activation and prevented alterations in microvascular hemodynamics induced by LPS in vivo, whereas it had no effect on the LPS-induced oxyradical generation from adherent leukocytes in vitro. The present study demonstrates that proteases such as plasmin may play an important role in the pathogenesis of endotoxin-induced microvascular disturbances.

Lymphokine production by mesenteric lymph node cells from BALB/C mice during Hymenolepis nana infection

Mesenteric lymph node cells (MLNC) prepared from BALB/c mice during infection with Hymenolepis nana proliferated extensively when cultured in the presence of soluble egg antigen, as assessed by measuring 3H-thymidine incorporation. Analysis of Hymenolepis-specific proliferative cells in MLNC by using monoclonal antibody specific for mouse T lymphocyte surface antigens revealed that the proliferative response of MLNC was mediated by Thy-1.2+, L3T4+ cells, that is, helper T cells. Supernatant of MLNC cultured with egg antigen contained large amounts of interleukin-2 and interferon-gamma, but only low levels of interleukin-5. The titer of these cytokines did not correlate with the interval between oral infection and collection of MLNC. These results strongly indicate that the Th1 subtype of helper T lymphocytes respond well to stimulation of H. nana egg antigen and suggest that acute inflammatory responses are involved in host-protective immunity to H. nana.

Selective engraftment of memory CD4+ T cells with an unusual recirculation pattern and a diverse T cell receptor-V beta repertoire into scid mice

Young (H-2d, Ld+) severe combined immunodeficiency (scid) mice were injected intravenously with 10(5) CD4+CD8- T cells purified from spleen, thymus or lymph nodes (LN) of dm2 (H-2d, Ld-) donor mice. In the immunodeficient recipients, the lymphoid compartment in the splenic white pulp was repopulated with donor-type T cells and cellularity in the red pulp was increased. In addition, donor-type CD4+ T cells repopulated the peritoneal cavity, mesenteric LN and the lamina propria of the small intestine of scid mice, but were undetectable in thymus and peripheral (inguinal, axillary) LN. Histological examination of repopulated mesenteric LN showed expanded subcapsular sinuses, repopulated cortical areas, but poorly developed high endothelial venules (HEV) indicating deficient blood-LN lymphocyte recirculation. The engrafted CD4+ T cell population had the surface phenotype of memory T cells (CD44/Pgp-1high CD45RB(low) and expressed the Peyer's patch HEV-specific homing receptor CD49d (LPAM-1), but not the LN HEV-specific homing receptor LECAM-1. The CD4+ T cell population in spleen and mesenteric LN of transplanted scid mice displayed a diverse T cell receptor-V beta repertoire. Transfer of titrated numbers (10(3), 10(4), 10(5) cells per mouse) of CD4+ T cells into scid mice established donor-type T cell populations with this unusual homing pattern in all recipients. Repeated serial transfers of dm2 CD4+ T cells through young scid mice revealed an extensive in vivo expansion potential of transferred cells for > 18 months. The experimental system described represents an in vivo model to study the functional competence and the differentiation potential of a murine memory CD4+ T cell subset.

Influence of resistant and susceptible genotype, IL-1, and lymphoid organ on Trichinella spiralis-induced cytokine secretion

The relative importance of cell-mediated inflammatory responses and antibody-mediated responses in controlling parasitic helminth infection is debated. To study the relationship between these responses and resistance or susceptibility to primary Trichinella spiralis infection, we infected resistant AKR mice and susceptible B10.BR mice and analyzed the lymphokines IL-2, IFN-gamma, and IL-5 produced by their T cells as a function of time and lymphoid organ. IL-2-secretors occurred maximally between days 3 and 6 postinfection, whereas IL-5-secretors peaked between days 6 and 9. Previously, we found that IFN-gamma producers peaked before day 6, whereas IL-4 producers peaked between days 6 and 9. Most cytokine secretors were CD4+. The simultaneous development of IL-2- and IFN-gamma-secreting cells, and IL-4- and IL-5-secreting cells, suggests that the infection may be stimulating T cells to differentiate into cells capable of secreting specific cytokine sets, analogous to the postulated Th1 and Th2 subsets. In the spleen and mesenteric lymph nodes, cells from B10.BR mice secreted more IL-5 than cells from AKR mice, as we found previously for IL-4. For both strains, mesenteric lymph node cells produced more IL-5 than splenocytes. The AKR mesenteric lymph node cells produced more IL-2 than the B10.BR cells, but the reverse occurred in splenocytes. The AKR peripheral lymph node cells also secreted more IFN-gamma than the B10.BR cells, but the strains were equivalent for peritoneal exudate cell IFN-gamma production. Thus, the lymphoid organ microenvironment plays an important role in regulating cytokine-secreting cell development in this system. We also tested the possible regulatory role of IL-1. Exogenous rIL-1 alpha increased IFN-gamma secretion early but not late in mesenteric lymph node cells from both strains; this reflected an increased IFN-gamma-secreting cell frequency, not a change in IFN-gamma mRNA transcript level. Exogenous rIL-1 alpha did not consistently affect IL-2, IL-4, or IL-5 secretion. These data suggest that IL-1 alpha availability in vivo may regulate IFN-gamma-secreting cell development. In sum, early activation of IFN-gamma-secreting T cells in lymph nodes, with little subsequent activation of IL-4- and IL-5-secreting cells, distinguished the resistant from susceptible strain responses to T. spiralis infection, and IL-1 alpha and lymphoid organ environment influence IFN-gamma-secreting cell activation.