In situ analysis of the cutaneous CD4+ T cells selectively infiltrating the human skin upon exposure to ultraviolet radiation

T lymphocytes play a dominant role in the regulation of immune responses and it is generally believed that the phenotype of T cells is related to its functions. Considerable numbers of T cells reside in normal human epidermis and dermis. We studied the number and phenotype of cutaneous CD3+ T lymphocytes population in normal human volunteers in situ following ab single local exposure to physiological erythemal inducing doses of solar-simulated radiation. Biopsies were taken a different time points after irradiation and immunohistochemestry was performed on cryostat sections. Our study shows that UV radiation affects the T cell population whitin human skin by depleting the majority of epidermal T cells and initiating a selective influx of non-activated memory CD4+ T cells.