A transgenic model to analyze the immunoregulatory role of IL-10 secreted by antigen-presenting cells

IL-10 is a cytokine secreted by a wide variety of cells type that has pleio tropic stimulatory and suppressive activities on both lymphoid and myeloid cells in vitro. To analyze the consequences of high IL-10 secretion by APCs in immune responses, we produced transgenic mice expressing human IL-10 di rected by the MHC class II Ea promoter. Despite alterations in the developm ent of T and B cells, no gross abnormalities were detected in peripheral ly mphocyte populations or serum Ig levels. However, when immunized using cond itions that give either a Th2-type or a Th1-type response, IL-10 transgenic mice failed to mount a significant T or B cell immune response to OVA, IL- 10 transgenic mice were also highly susceptible to infection with intracell ular pathogens like Listeria monocytogenes or Leishmania major, in contrast to IL-10 transgenic mice, where the transgene was express in T cells. Fina lly, the recently described stimulatory effect of IL-10 on CD8(+) T cells w as confirmed by the ability of IL-10 transgenic mice to limit the growth of immunogenic tumors by a CTL-mediated mechanism. These results demonstrate, that, depending on the type of immune response, IL-IO can mediate immunosu ppressive or immunostimulatory activities in vivo.