ABSTRACT
The immunoglobulin (Ig)E immune response against protein antigens is profoundly influenced by the antigen dose used for immunization. Whereas immunization of CBA/J mice with low antigen doses results in the production of large amounts of IgE antibody, priming with high antigen doses leads to only marginal IgE antibody production in animals. However, in vitro restimulation of spleen cells from mice primed with high antigen doses leads to considerable activation of IgE-producing B cells, which suggests that B cells primed for IgE antibody production do exist among spleen cells. We investigated the modalities of activation of these memory B cells. The data presented here reveal that the anamnestic IgE immune response in vitro is strictly dependent on the presence of IgG1-expressing B cells, which differentiate after a sequential isotype switch into IgE-producing plasma cells with the help of primed CD4+ T cells. The induction of IgE-producing plasma cells requires a cognate interaction between B cells and CD4+ T cells. Interleukin (IL)-4 seems not to be involved in this process, since IgE production in vitro is resistant to suppression by anti-IL-4 monoclonal antibody. Finally, we show that IgG1-expressing B cells represent a relevant memory cell population in vivo also, but in contrast to the in vitro situation the final differentiation into IgE-producing plasma cells is dependent on IL-4.
Subject(s)
Immunoglobulin Class Switching/immunology , Immunoglobulin E/biosynthesis , Immunoglobulin G/biosynthesis , Interleukin-4/immunology , Animals , Antigens/administration & dosage , Antigens/immunology , B-Lymphocytes/cytology , B-Lymphocytes/immunology , CD4-Positive T-Lymphocytes/immunology , Cell Division , Hemocyanins/administration & dosage , Hemocyanins/immunology , Mice , Mice, Inbred BALB C , Mice, Inbred CBAABSTRACT
The quality of the humoral immune response against protein antigens in CBA/J mice is dependent on the antigen dose used for immunization: low doses induce high titers of IgE antibodies, whereas high doses promote the production of IgG2a antibodies but inhibit IgE formation. To investigate whether the reciprocal regulation of antibody production is possibly due to a differential activation of Th1 and Th2 cell populations in the two immunization groups, the cytokine pattern of spleen cells from both groups, cultured with antigen in vitro, was analyzed by measurement of intracellular and secreted cytokine levels. The data presented show that in vitro restimulated spleen cells from mice primed with low as well as with high doses of antigen produce predominantly the Th2 cytokines IL-4 and IL-10 but reduced levels of IL-12. The release of IFN-gamma is only slightly enhanced compared to unstimulated control cultures. The results indicate that CD4+ T cells in both groups belong mainly to the Th2 cell subset. This finding is contradictory to the general allegation that the antigen dose is decisive for the polarization of Th1 versus Th2 immune responses and shows that the antigen dose-dependent regulation of IgE antibody production is not due to differential polarization towards Th1 and Th2 cells.