IL-3 in combination with IL-4, induces the expression of functional CD1 molecules on monocytes.

CD1 molecules have recently been shown to present bacterial antigens to CD4-CD8-TCR alpha beta + T lymphocytes. The expression of CD1 on monocytes can be induced by GM-CSF and is further enhanced by IL-4. GM-CSF and IL-3 receptors share a common chain and often have similar activities; however, only IL-3, but not GM-CSF, can stimulate CD4-CD8-TCR alpha beta + T lymphocytes directly. In this study we show that IL-3, in combination with IL-4, can also induce the expression of CD1 on monocytes to a level comparable to that induced by GM-CSF/IL-4. This induction of CD1 by IL-3 can be suppressed by IL-10. Furthermore, CD1-induced antigen presentation was similar whether CD1 was induced by IL-3/IL-4 or GM-CSF/IL-4. The ability of IL-3 to induce expression of CD1 molecules and to directly stimulate CD4-CD8- alpha beta + TCR T lymphocytes raises interest in the role of this cytokine in the development, differentiation and function of this T cell subset.