Interleukin-21 maintains the expression of CD16 on monocytes via the production of IL-10 by human naïve CD4+ T cells

► IL-21 induces IL-10 production from human activated naïve CD4+ T cells. ► IL-21 increases expression of IL-21R on CD4+ T cells. ► IL-21 induces phosphorylation of STAT1, STAT3 and STAT5 in activated CD4+ T cells. ► IL-21 maintains the expression of CD16 on monocytes via its production of IL-10.