IL-15 IS A NOVEL GROWTH-FACTOR FOR MURINE GAMMA-DELTA T-CELLS INDUCEDBY SALMONELLA INFECTION

We have previously shown evidence for the early recruitment of gamma d elta T cells during the disease course of primary infections with List eria monocytogenes or Salmonella choleraesuis in mice, Since gamma del ta T cells at this stage of the disease do not produce IL-2, the growt h factor for the gamma delta T cells remains unknown, IL-15 is a novel cytokine that uses beta- and gamma-chain of IL-2R for signal transduc tion, and is produced by activated monocytes/macrophages. In this stud y, we investigated the proliferative activity of IL-15 for gamma delta T cells appearing after primary infection with S, choleraesuis 31N-1, The gamma delta T cells, which expressed beta- and gamma-chains of IL -2R, proliferated in the presence of rlL-15 and produced appreciable l evels of gamma-IFN and IL-4, Addition of anti-IL-2R beta mAb significa ntly inhibited the IL-15-induced proliferation of the ya T cells, Furt hermore, the gamma delta T cells produced gamma-IFN in response to mon ocyte/macrophage cell line, J774A.1 infected with S, choleraesuis, whi ch expressed an abundant level of IL-15 mRNA. This cytokine production was inhibited significantly by anti-IL-15 Ab, Taken together, these r esults suggest that IL-15 derived from infected macrophages may contri bute to the early activation of gamma delta T cells during salmonellos is.