How important is the L3T4 antigen to L3T4+ cell function in vivo?

Dextran sulfate sodium (DSS) induced experimental colitis in immunodeficient mice: effects in CD4(+) -cell depleted, athymic and NK-cell depleted SCID mice

Administration of dextran sulfate to mice, given in the drinking water results in acute or subacute colonic inflammation, depending on the administration protocol. This colonic inflammation exhibits ulceration, healing and repair, and a therapeutic response that makes it valuable for the study of mechanisms that could act in the pathogenesis of human ulcerative colitis, a disease thought to have an immunologically dependent pathogenesis. To investigate if immunological mechanisms were involved in the induction of colonic inflammation in this model, mice with different degrees of immunodeficiency were used. It was shown that dextran sulfate induced colitis could be induced in Balb/c mice depleted of CD4(+) helper T cells by treatment with monoclonal antibodies preceded by adult thymectomy. The depletion of CD4(+) was verified by flow cytometric analysis. Furthermore, the colonic inflammation could equally be induced in athymic CD-1 nu/nu mice lacking thymus-derived T cells, in T and B-cell deficient SCID mice, and also in SCID mice depleted of NK cells by treatment with anti-asialo GM1 antibodies. The NK-cell depletion was verified by measuring spleen NK-cell activity. The resulting colonic inflammation in all these types of deficient mice was qualitatively comparable, as shown by clinical and histological appearance. These results indicate that the presence of functional T, B and NK cells is not crucial for the induction of dextran sulfate colitis in mice.

Elevated CD4 antigen expression among activated T cells in lymph nodes draining mammary regions chronically exposed to Staphylococcus aureus antigen

We examined the cell cycle distribution and subset marker characteristics of mucosal-associated supramammary lymph node (MALN) T cell subpopulations at sites proximal and distal to the mammary region of animals repeatedly injected with Staphylococcus aureus antigen. Multiparameter flow cytometric analysis of draining MALNs showed that CD4+ T cells expressed significantly greater amounts of CD4 surface antigen than corresponding cell populations in non-draining MALNs. In contrast, the intensity of CD8 surface antigen expression among draining MALN CD8+ cells remained unchanged. Draining and non-draining MALNs contained nearly equal proportions of large CD4+ T cell subpopulations (CD4/CD8 ratio) with the former having greater cell numbers undergoing active DNA synthesis (S + G2M phase) in vivo. Similarly, draining MALNs had greater cell numbers of small CD4+ lymphocytes in the S + G2M phase, although with lower CD4/CD8 ratios of corresponding cell populations in non-draining MALNs. This study demonstrates that prolonged exposure with Staph aureus antigen enhances the cell number and expression of CD4 surface antigen among T lymphocyte subpopulations actively synthesizing DNA in draining MALNs. The role of the CD4 antigen in inflammatory responses at sites proximal (draining) and distal (non draining) to chronic infection within the mammary/mucosal immune network is discussed.

Host defense against cholera toxin is strongly CD4+ T cell dependent

This study investigates the role of CD4+ T cells in host defense against cholera enterotoxin-induced diarrhea. Antitoxin immunoglobulin A formation and gut protection against cholera toxin (CT) following oral immunizations with CT were evaluated in normal mice and mice that had been depleted of CD4+ T cells by in vivo treatment with specific anti-CD4 monoclonal antibodies. Flow cytometer analysis demonstrated that anti-CD4 monoclonal antibody effectively eliminated CD4+ T cells in the spleen, mesenteric lymph nodes, and Peyer's patches. In contrast, lamina propria lymphocytes demonstrated only some decrease in CD4+ T-cell numbers following antibody treatment. However, CD4 expression of individual lamina propria lymphocytes was strongly down-regulated. Depletion of CD4+ T cells performed prior to oral immunization with CT completely inhibited the ability to respond to CT. No antitoxin production, as detected at the single-cell level by the ELISPOT technique, was found in the spleen, mesenteric lymph nodes, or Peyer's patches, nor did we observe serum antitoxin responses in these mice. Control mice demonstrated strong antitoxin responses in all locations following oral immunization with CT. Anti-CD4 antibody treatment also effectively inhibited the antitoxin immunoglobulin A response in the lamina propria to CT as well as blocked the ability to develop gut protection against CT challenge of ligated intestinal loops after oral CT immunization. Thus, in vivo CD4+ T-cell depletion rendered these mice unable to develop protective immunity in the gut following oral immunization with CT. Moreover, CD4+ T-cell depletion effectively inhibited the antitoxin immune response in the gut lamina propria, mesenteric lymph nodes, Peyer's patches, and spleen when performed prior to both priming and booster immunizations with CT. This study clearly demonstrates the requirement of functional CD4+ T cells in the gut immune system for the development of host defense against CT-induced disease. Our data also reinforce the concept of a strong association between gut protection against CT and local production of neutralizing immunoglobulin A antitoxin.

Distinct IL-3 activation profile induced by intravenous versus subcutaneous routes of immunization

Lymphoid cells from mice immunized i.v. or s.c. with Leishmania major antigens were analyzed for their capacity to produce lymphokines when stimulated with specific antigens in vitro. Spleen cells from BALB/c mice immunized by the s.c. route produced significantly higher levels of IL-3 and IL-3 mRNA than those from mice immunized by the i.v. route. The differential production of IL-3 was maintained at a wide range of antigen concentrations tested in vitro and for different culturing times. T cell enrichment procedures and treatment with CD4+ mAb in vitro confirmed the T cell nature of the IL-3 producer population. However, the IL-3 production in the two populations of spleen cells was equally high after Con A stimulation in vitro. The IL-2 production by the two populations of cells was also not significantly different after antigen or mitogen stimulation in vitro. To our knowledge, this is the first report of a differential synthesis of IL-3 mRNA and secretion of IL-3 induced by different routes of immunization followed by specific-antigen stimulation in vitro. These findings may also explain earlier observations that i.v. immunization with leishmanial antigen induces protection, whereas s.c. immunization leads to exacerbation of L. major infection, since IL-3 has been previously shown to promote leishmanial infection. The fact that the phenomenon also extends to other antigen systems suggests that this finding may have a broader implication in immune regulation and vaccine development.

Recurrence of insulitis in the NOD mouse after early prolonged anti-CD4 monoclonal antibody treatment

The treatment of young NOD mice with continuous anti-CD4 mAb administration has previously been shown to prevent insulitis from developing. It has also been shown that insulitis, once present, can be abolished by anti-CD4 mAb treatment, but that the insulitis recurs after treatment stops. We have studied the effect of treating young NOD/Wehi mice with a limited course of anti-CD4 mAb to determine if any long term prevention of insulitis ensued. Anti-CD4 mAb (H129.19) was given i.p. weekly to 10 female NOD/Wehi mice from 25-100 days of age. Control mice received no treatment. The pancreas of the mice were examined histologically at 100 and 180 days of age and severity of insulitis graded from 0-100%. The insulitis grade in treated mice at 100 days was 5 +/- 2% compared with 29 +/- 26% in age matched control mice (p less than 0.01). At 180 days of age the insulitis grade in treated mice was 29 +/- 23% compared with 47 +/- 22% in aged matched controls (NS). Thus insulitis was prevented from developing by early treatment with anti-CD4 mAb but developed later when treatment was stopped. Early anti-CD4 mAb treatment does not therefore appear to produce a tolerant state so averting insulitis development and, insulitis can still develop in older NOD mice.