T cell subsets in normal human epidermis.

Freshly isolated human lymphocytes from normal epidermis were characterized with respect to distribution of subsets. The major T cell receptor-alpha beta + compartment was enriched for CD4+, for CD8 alpha alpha +, and for CD4-CD8-T lymphocytes compared with peripheral blood lymphocytes. Furthermore, the majority of epidermal T lymphocytes expressed a CD45RA- CD45ROhigh Fas+ memory/effector phenotype; many also expressed early-intermediate activation markers, suggesting antigenic exposure in vivo. The cutaneous lymphocyte-associated antigen was expressed by almost all epidermal T lymphocytes. A large portion also expressed the mucosal-associated alpha e beta 7-integrin, which may mediate retention to epithelium. These data show that T lymphocytes present in normal human epidermis constitute a distinct T cells compartment with characteristics similar to that of other epithelial-associated T cell compartments.