DIFFERENTIAL REGULATION OF IGA PRODUCTION BY TGF-BETA AND IL-5 - TGF-BETA INDUCES SURFACE IGA-POSITIVE CELLS BEARING IL-5 RECEPTOR, WHEREAS IL-5 PROMOTES THEIR SURVIVAL AND MATURATION INTO IGA-SECRETING CELLS

Transforming growth factor β (TGF-/3) and IL-5 have been shown to augment IgA production by LPS-stimulated murine B cells. We investigated the effect of TGF-β on the expression of surface Ig-isotype and IL-5 receptor on LPS-stimulated B cells. TGF-β increased the proportion of both surface IgA-positive (sIgA+) B cells and sIgG2b+ B cells and enhanced IgA and IgG2b production by LPS-stimulated B cells. TGF-β synergized with IL-5 only for IgA production of the seven Ig-isotypes and in combination with IL-5 caused a significant increase in the proportion of sIgA+ B cells up to 17.4%. In contrast, IL-5 decreased the proportion of sIgG2b+ B cells and sIgG3+ B cells and inhibited the production of IgG2b and IgG3 by LPS-stimulated B cells. About 50% of sIgA+ cells induced by TGF-β expressed IL-5 receptor. They secreted peak levels of IgA and seemed to maintain long viability in the presence of IL-5; whereas TGF-β had the opposite effects on sIgA+ B cells and down-regulated the IL-5 receptor expression. These results indicate that TGF-β increases the number of sIgA+- and IL-5 receptor-positive B cells which respond to IL-5 giving rise to IgA-secreting cells and also support the notions that TGF-β preferentially induces switching to sIgA+ B cells and IL-5 induces the maturation of postswitch sIgA+ B cells into IgA-secreting cells in a stepwise fashion. © 1992.