The activation requirements of dendritic epidermal T cells

Dendritic epidermal T cells (DETC) are a minor subpopulation of the murine epidermis and express the T cell receptor (TCR) $\gamma\delta$-chains. In order to study the function of DETC cells, several DETC cell lines were characterized for activation by cytokines, by stimulation with mitogens, and by stimulation via the TCR/CD3 complex. These cell lines could only be stimulated with IL-2 alone and IL-4 plus IL-1; stimulation with Con A or anti-CD3 required the costimulatory action of IL-1. These DETC cell lines resembled Th1 T cells in that their proliferative responses were mediated by the autocrine production of IL-2, but resembled Th2 cells because they required IL-1 as a costimulatory factor. The production of IL-1 by keratinocytes in the epidermis may play a critical role in the activation of DETC cells in vivo.