PROLONGED IN-VIVO IL-4 TREATMENT INHIBITS ANTIGEN-SPECIFIC IGG(1) ANDIGE FORMATION

IL-4 is obligatory for primary IgE responses, whereas primary IgG(1) a nd secondary IgE responses are partially IL-4 independent. To investig ate the effect of IL-4 on the antigen-specific memory formation for th ese isotypes, BALB/c mice were treated after primary TNP-KLH immunizat ion with recombinant IL-4 for a period of 4 months. This prolonged pre sence of a high IL-4 level resulted in increased serum levels of total IgG(1) and IgE, whereas total IgG(2a) did not change. The expression of CD23, but not I-A(d), increased on the splenic B cells. IL-4 treatm ent did not affect the IL-4 production by Con A stimulated spleen cell s, whereas it did decrease the IFN-gamma production. In the same mice the TNP-specific IgG(1) and IgE serum levels, however, were decreased. Similar results were found when the antigen was continuously present during the IL-4 treatment. Furthermore, it was shown that IL-4 decreas ed the formation of IgG(1) and IgE memory cells. These results point t o different effects of IL-4 in regulating antigen-specific and bystand er responses.