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Abstract Background Interleukin 9 (IL-9) is produced by activated CD4+ T cells. Its effects include stimulation of mucus production, enhanced mast cell proliferation, enhanced eosinophil function, and IgE production. These effects are consistent with a role in allergic diseases. Glucocorticoids have potent anti-inflammatory effects, including suppression of cytokine synthesis, and are widely used in the treatment of allergic conditions. Methods We examined the effect of the glucocorticoid dexamethasone (Dex) on IL-9 mRNA expression and protein secretion with real-time RT-PCR and ELISA. Peripheral blood mononuclear cells (PBMC) were prepared from human volunteers and activated with OKT3. CD4+ T cells were purified from PBMC and activated with OKT3 plus PMA. Results IL-9 mRNA abundance and protein secretion were both markedly reduced following treatment of activated PBMC with Dex. mRNA levels were reduced to 0.7% of control values and protein secretion was reduced to 2.8% of controls. In CD4+ T cells, Dex reduced protein secretion to a similar extent. The IC50 value of Dex on mRNA expression was 4 nM. Conclusion These results indicate that IL-9 production is very markedly inhibited by Dex. The findings raise the possibility that the beneficial effects of glucocorticoids in the treatment of allergic diseases are in part mediated by inhibition of IL-9 production.

Background: Interleukin 9 (IL-9) is produced by activated CD4+ T cells. Its effects include stimulation of mucus production, enhanced mast cell proliferation, enhanced eosinophil function, and IgE production. These effects are consistent with a role in allergic diseases. Glucocorticoids have potent anti-inflammatory effects, including suppression of cytokine synthesis, and are widely used in the treatment of allergic conditions., Methods: We examined the effect of the glucocorticoid dexamethasone (Dex) on IL-9 mRNA expression and protein secretion with real-time RT-PCR and ELISA. Peripheral blood mononuclear cells (PBMC) were prepared from human volunteers and activated with OKT3. CD4+ T cells were purified from PBMC and activated with OKT3 plus PMA., Results: IL-9 mRNA abundance and protein secretion were both markedly reduced following treatment of activated PBMC with Dex. mRNA levels were reduced to 0.7% of control values and protein secretion was reduced to 2.8% of controls. In CD4+ T cells, Dex reduced protein secretion to a similar extent. The IC 50 value of Dex on mRNA expression was 4 nM., Conclusion: These results indicate that IL-9 production is very markedly inhibited by Dex. The findings raise the possibility that the beneficial effects of glucocorticoids in the treatment of allergic diseases are in part mediated by inhibition of IL-9 production.

Viral infections are involved in the pathogenesis of blood autoimmune diseases such as hemolytic anemia and thrombocytopenia. Although antigenic mimicry has been proposed as a major mechanism by which viruses could trigger the development of such diseases, it is not easy to understand how widely different viruses might induce these blood autoimmune diseases by this sole mechanism. In mice infected with lactate dehydrogenase-elevating virus (LDV), or mouse hepatitis virus, and treated with anti-erythrocyte or anti-platelet monoclonal autoantibodies at a dose insufficient to induce clinical disease by themselves, the infection sharply enhances the pathogenicity of autoantibodies, leading to severe anemia or thrombocytopenia. This effect is observed only with antibodies that induce disease through phagocytosis. Moreover, the phagocytic activity of macrophages from infected mice is increased and the enhancing effect of infection on autoantibody-mediated pathogenicity is strongly suppressed by treatment of mice with clodronate-containing liposomes. Finally, the disease induced by LDV after administration of autoantibodies is largely suppressed in animals deficient for gamma-interferon receptor. Together, these observations suggest that viruses may trigger autoantibody-mediated anemia or thrombocytopenia by activating macrophages through gamma-interferon production, a mechanism that may account for the pathogenic similarities of multiple infectious agents.

Antigenic mimicry has been proposed as a major mechanism by which viruses could trigger the development of immune thrombocytopenic purpura (ITP). However, because antigenic mimicry implies epitope similarities between viral and self antigens, it is difficult to understand how widely different viruses can be involved by this sole mechanism in the pathogenesis of ITP. Here, we report that in mice treated with antiplatelet antibodies at a dose insufficient to induce clinical disease by themselves, infection with lactate dehydrogenase-elevating virus (LDV) was followed by severe thrombocytopenia and by the appearance of petechiae similar to those observed in patients with ITP. A similar exacerbation of antiplatelet-mediated thrombocytopenia was induced by mouse hepatitis virus. This enhancement of antiplatelet antibody pathogenicity by LDV was not observed with F(ab')2 fragments, suggesting that phagocytosis was involved in platelet destruction. Treatment of mice with clodronate-containing liposomes and with total immunoglobulin G (IgG) indicated that platelets were cleared by macrophages. The increase of thrombocytopenia triggered by LDV after administration of antiplatelet antibodies was largely suppressed in animals deficient for gamma-interferon receptor. Together, these results suggest that viruses may exacerbate autoantibody-mediated ITP by activating macrophages through gamma-interferon production, a mechanism that may account for the pathogenic similarities of multiple infectious agents.

Although T helper 2 (Th2) cytokines are known to be critical in the generation of protective immunity against intestinal helminths in mouse models, it is unclear whether they are important in natural immunity against gut helminthiases in humans. Therefore, we investigated cytokine production in ex vivo whole-blood cultures in response to Ascaris lumbricoides antigen and mitogen in a cross-section of a community where the parasite is hyperendemic. The intensity of A. lumbricoides infection was significantly reduced after age 11 years. Levels of cytokines associated with Th2 lymphocytes (interleukin [IL]-4, IL-9, IL-10, and IL-13) demonstrated an inverse relationship with intensity of A. lumbricoides infection only in individuals aged >11 years. Furthermore, the IL-9, IL-10, and IL-13 produced in response to parasite antigen were of primary importance in this relationship. These findings promote a role for Th2-mediated responses in the age-dependent reduction of intestinal helminth infections in humans.

Background: The depletion of differential B cell and xenoreactive natural antibodies (XNA) by anti-delta and anti-mu injections was analyzed in adult mice. Sequential treatment with anti-delta and then anti-mu induces a complete depletion of B cells and XNA and represents a potential approach to induce xenograft tolerance., Methods: Adult mice were injected with anti-mu, anti-delta, anti-delta then anti-mu, or control isotype monoclonal antibodies from day 0 to day 14. The different B-cell populations were analyzed by FACS and immunohistology. Ig production was tested by ELISA. XNA were analyzed by FACS., Results: Anti-mu injections induced a depletion of IgMhigh, immature B cells, marginal zone B cells, and B1 cells and an increase of IgG-XNA production. Anti-delta injections induced mature conventional IgDhigh B-cell depletion and increased IgM-XNA production. Interestingly, sequential injections of anti-delta then anti-mu induced a depletion of immature B cells, mature B cells (MZ, B2, and B1), and XNA., Conclusions: These results demonstrate that mature B-cell depletion in adult mice can be obtained by mAb injections and depends on the surface immunoglobulin cross-linking threshold. Indeed, anti-mu mAb depleted IgMhigh B cells (MZ and B1) and anti-delta, IgDhigh B cells (B2). The differential B-cell suppression shows that conventional B cells are responsible in the IgG-XNA production and MZ and B1 cells in the IgM-XNA production. Sequential repeated injections of anti-delta then anti-mu mAb depleted all B-cell populations and suppressed the whole XNA production.

Background: Given the role of xenoreactive natural antibodies (XNA) in the pathogenesis of xenograft rejection, we tested whether the administration of anti-mu or anti-delta monoclonal antibodies (mAbs) in adult rats would suppress the generation of XNA., Methods: Adult LOU/C (Igkappa-1a) rats were treated with anti-mu or anti-delta mAbs after nonlethal total body irradiation and bone marrow transplantation from congenic LOU/C (Igkappa-1b) rats. The differentiation of donor bone marrow (BM)-driven Igkappa-1b+ B cells and XNA production were analyzed., Results: Both anti-mu and anti-delta mAbs arrested B-cell differentiation in the BM. In anti-mu-treated rats, there was a total depletion of donor-driven, peripheral Igkappa-1b+ B cells, secreting cells, and circulating XNA of the Igkappa-1b allotype. In anti-delta-treated rats, a significant number of Igkappa-1b+ B cells, which did not express membrane IgD, "escaped" deletion and partially repopulated peripheral lymphoid organs. This B-cell population was active in the production of XNA, as revealed by the high serum levels of XNA in these animals., Conclusions: Anti-mu administration resulted in arrest of B-cell differentiation and in down-regulation of IgM and IgG XNA production in adult rats. These data suggest that the use of anti-mu mAbs may be a useful approach to suppress the production of XNA and prevent xenograft rejection. Furthermore, we suggest that the B-cell population responsible for the production of XNA in adult rats belongs to a B-cell lineage expressing low levels of membrane IgD and "escaping" deletion in the BM upon anti-delta treatment.

We have previously described the cloning and sequencing of a gene portion coding for the terminal part of a 34-kDa protein of Mycobacterium avium subsp. paratuberculosis, the etiological agent of Johne's disease (P. Gilot, M. De Kesel, L. Machtelinckx, M. Coene, and C. Cocito, J. Bacteriol. 175:4930-4935, 1993). The recombinant polypeptide (a362) carries species-specific B-cell epitopes which do not cross-react with other mycobacterial pathogens (M. De Kesel, P. Gilot, M.-C. Misonne, M. Coene, and C. Cocito, J. Clin. Microbiol. 31:947-954, 1993). The present work describes the preparation of polyclonal and monoclonal antibodies directed against a362 and the use of these immunoglobulins for histopathological diagnosis of Johne's disease. The new immunohistological procedures herewith detailed proved to be able to identify M. avium subsp. paratuberculosis antigens in the intestinal tissues and lymph nodes of cattle affected by either the paucibacillary or pluribacillary form of the disease. They yielded negative responses not only with healthy animals but also with those affected by tuberculosis (Mycobacterium bovis). Both immunohistological procedures proved to be as sensitive as or more sensitive than Ziehl-Neelsen staining and, in addition, to be endowed with species specificity.

A prospective trial was conducted in 129 recipients of primary liver transplantation, to compare induction immunosuppression using triple drug therapy (cyclosporine, steroids, and azathioprine; group 1, n = 42), versus triple drug therapy with a 10-day course of OKT3 (group 2, n = 44) or of the anti-interleukin-2 receptor monoclonal antibody LO-Tact-1 (group 3, n = 43). Two-year actual patient survival rates were 64%, 79%, and 93% in groups 1, 2, and 3, respectively (1 vs. 2, NS; I vs. III, P = 0.003; 2 vs. 3, NS). Up to 2 years after transplantation, 18%, 44%, and 53% of the grafts in groups 1, 2, and 3, respectively, had not experienced steroid-resistant acute rejection (1 vs. 2, P = 0.002; 1 vs. 3, P = 0.007; 2 vs. 3, NS). The overall incidence of chronic rejection was 4%. OKT3 therapy, but not LO-Tact-1, significantly increased the incidence of cytomegalovirus infections (P = 0.019). In conclusion, immunoprophylaxis with LO-Tact-1 seemed to provide a liver graft acceptance rate at least as satisfactory as that with OKT3, without an increase in the incidence of infections.