CD1d on myeloid dendritic cells stimulates cytokine secretion from and cytolytic activity of Vα24JαQ T cells:: A feedback mechanism for immune regulation

The precise immunologic functions of CD1d-restricted, CD161(+) AV24AJ18 (V alpha 24J alpha Q) T cells are not well defined, although production of IL-4 has been suggested as important for priming Th2 responses, However, activation of human V alpha 224J alpha Q T cell clones by anti-CD3 resulted in the secretion of multiple cytokines notably important for the recruitment and differentiation of myeloid dendritic cells. Specific activation of V alpha 24J alpha Q T cells was CD1d restricted. Expression of CD1d was found on monocyte-derived dendritic cells in vitro, and immunohistochemical staining directly revealed CD1d preferentially expressed on dendritic cells in the paracortical T cell zones of lymph nodes. Moreover, myeloid dendritic cells both activated V alpha 24J alpha Q T cells and were susceptible to lysis by these same regulatory T cells. Because myeloid dendritic cells are a major source of IL-12 and control Th1 cell differentiation, their elimination by lysis is a mechanism for limiting the generation of Th1 cells and thus regulating Th1/Th2 responses.