IgG1 production by slgD(+) splenic B cells and peritoneal B-1 cells in response to IL-5 and CD38 ligation

CD38 ligation on mouse B cells by CS/2, an anti-mouse CD38 mAb, induces pro liferation, IL-5 receptor a chain expression and tyrosine phosphorylation o f Bruton's tyrosine kinase, Furthermore, stimulation of splenic B cells wit h IL-5 together with CS/2 induces Blimp-1 expression and differentiation in to Ig-producing cells, Here we examined the role of IL-5 in IgG1 and IgA pr oduction by B cells isolated from the spleen and peritoneal cavity. CD38 re cognized by CS/2 was expressed in the follicular mantle B cells surrounding the germinal center, slgD(+) splenic B cells and peritoneal B cells, IL-5 induced IgG1 production in splenic slgD(+) B cells stimulated with CS/2, wh ile it was ineffective to induce IgA production. Among the various cytokine s tested, only IL-5 had a synergistic effect on IgG1 production with CS/2, IL-5 could induce the generation of S-mu-S(gamma)1, reciprocal recombinatio n DNA products in CS/2-stimulated B cells, IL-4 was ineffective to induce e ither mu-gamma 1 switch recombination or IgG1 secretion with CS/2, demonstr ating that IL-5 promotes both mu-gamma 1 switch recombination and IgG1 secr etion in an IL-4-independent manner. The peritoneal B-2 cells exhibited bot h IgG1 and IgA production in response to IL-5 plus CS/2, while B-1 cells pr oduced IgG1. These results imply that the pattern of differentiation to Ig- producing cells seen with peritoneal B cells is not identical to the patter n seen with splenic B cells and that peritoneal B-2 cells contain precursor s of IgA-producing cells responding to IL-5 plus CS/2.