INTERLEUKIN-10 INDUCES IMMUNOGLOBULIN-G ISOTYPE SWITCH RECOMBINATION IN HUMAN CD40-ACTIVATED NAIVE B-LYMPHOCYTES

Upon activation, B lymphocytes can change the isotype of the antibody they express by immunoglobulin (Ig) isotype switch recombination. In p revious studies on the regulation of human IgG expression, we demonstr ated that interleukin 10 (IL-10) could stimulate IgG1 and IgG3 secreti on by human CD40-activated naive (sIgD(+)) tonsillar B cells. To asses s whether IL-10 actually promotes the DNA recombination underlying swi tching to these isotypes, we examined the effect of IL-10 on the gener ation of reciprocal products that form DNA circles as by-products of s witch recombination. The content of reciprocal products characteristic of mu-gamma recombination was elevated after culture of CD40-activate d tonsillar sIgD(+) B cells with either IL-4 or IL-10, although high l evels of IgG secretion were observed only with IL-10. Unlike IL-4, IL- 10 did not induce reciprocal products of mu-epsilon and gamma-epsilon switch recombination. These results demonstrate that IL-10 promotes bo th switching to gamma and IgG secretion.