HUMAN INTERLEUKIN-10 INDUCES NAIVE SURFACE-IMMUNOGLOBULIN D-CELLS TO SECRETE IGG1 AND IGG3( (SIGD(+)) B)

During antigen-induced immune responses, human B cells switch isotype from immunoglobulin M (IgM)-IgD to IgG1-4, IgA1-2, or IgE. In the huma n, no cytokines have yet been demonstrated to act as switch factors fo r IgG1, IgG2, and IgG3. In this paper, we report that in response to i nterleukin 10 (IL-10), anti-CD40 activated tonsillar surface IgD(+) (s IgD(+))B cells are induced to secrete large amounts of IgM, IgG1, and IgG3 but neither IgG2 nor IgG4. Cord blood purified B cells and lympho cytes from Hyper-IgM patients also produced IgG1 and IgG3 after cultur e with anti-CD40 and IL-10. In contrast, sIgD(-) isotype-committed B c ells produce IgG1, IgG2, and IgG3 when activated through CD40 in the p resence of IL-10. Thus, in addition to its growth-promoting and differ entiating activities on human B cells, IL-10 may represent a switch fa ctor for IgG1 and IgG3.