CD4 and brucellosis: Moreover, a 5-fold greater number of IL-10 producing CD4+CD25+ T cells was detected at 9 d.p.i., compared to IL-10 producing CD4+CD25− T cells (Fig. 3D and 3E), suggesting that the CD4+CD25+ T cell subset is the major population responsible for IL-10 production during acute brucellosis in the mouse.