SUPPRESSION OF T-HELPER TYPE-1 IMMUNE-RESPONSE AGAINST LISTERIA-MONOCYTOGENES BY TREATMENT OF MICE WITH GOAT ANTIBODIES TO MOUSE IGD

Injection of goat anti-mouse IgD antibodies (GAM IgD) to mice has been shown to induce polyclonal IgG1 and IgE production by B cells and int erleukin-4 (IL-4) production by goat Ig-specific T cells. Surface IgD cross-linking also activates B cells to function as antigen-presenting cells (APC). Although the GAM IgD treatment is a well-established sys tem for analysis of B-cell dependent antigen presentation, the influen ce of GAM IgD treatment on the immune response to ii-relevant antigens is not known. To address this issue, we analysed effects of GAM IgD t reatment on (1) the mitogen response of freshly isolated T cells, and (2) the listerial antigen-specific response after immunization with vi able Listeria monocytogenes, which induces CD4(+) interferon-gamma (IF N-gamma) producing protective T cells in normal mice. Spleen CD4(+) T cells from the GAM IgD-treated mice produced higher levels of IL-4 but lower levels of IFN-gamma and IL-2 than those from the control mice w hen they were stimulated with concanavalin A (Con A) in vitro. When sp leen T cells were stimulated with listerial antigen 10 days after a lo w dose (1/20 LD(50)) of L. monocytogenes infection, CD4(+) T cells fro m the GAM IgD-treated mice showed increased IL-4 production and decrea sed IFN-gamma and IL-2 production compared with those from the control L. monocytogenes-infected mice. Furthermore, the GAM IgD treatment re sulted in a reduction of the survival rate after a high dose (1/2 LD(5 0)) of L. monocytogenes infection. These results suggest that treatmen t of mice with GAM IgD suppresses the T-helper type-1 (Th1)-type T-cel l response and induces a Th2-type response against irrelevant antigens , even when they are injected after GAM IgD treatment.