EFFECT OF INTERLEUKIN-10 ON DENDRITIC CELL MATURATION AND FUNCTION

The main function of dendritic cells (DC) is to induce the differentia tion of naive T lymphocytes into helper cells producing a large array of lymphokines, including interleukin (IL)-2; interferon-gamma (IFN-ga mma), IL-4, IL-5 and IL-10. The potent immunostimulatory properties of DC develop during a process of maturation that occurs spontaneously i n vitro. Since IL-10 has been shown to inhibit Th1 responses, we deter mined its effect on DC maturation and accessory function. Our data sho w that DC that have undergone maturation in vitro in the presence of I L-10, have an impaired capacity to induce a Th1-type response in vivo, leading to the development of Th2 lymphocytes. Their inability to pro mote the synthesis of IFN-gamma seems to correlate with a decreased pr oduction of IL-12, an bet erodimeric cytokine necessary for optimal ge neration of Th1-type cells. These results suggest that IL-10 skews the Th1/Th2 balance to Th2 in vivo by selectively blocking IL-12 synthesi s by the antigen-presenting cells that play a role of adjuvant of the primary immune response. The cytokines present in the environment at t he presentation step may, therefore, determine the class of the immune response induced by DC in vivo, i.e. Th0, Th1 and/or Th2.