Selective T cell killing of human lymphocytes by ultraviolet radiation

The effects of ultraviolet radiation (uv) on human B and T lymphocytes were studied. In vitro studies showed that T lymphocytes were more sensitive to uv than B lymphocytes as assessed by eosin-dye exclusion. Following uv exposure, the viable lymphocytes responded to mitogens (PHA, PWM), and functional B lymphocytes were present at a time when no viable T cells were detected. Varying doses of uv were required to abrogate different in vitro responses (proliferative response to antigen or allogeneic cells, MIF production, and cell-mediated lympholysis). In vivo, uv was able to diminish an established cutaneous delayed hypersensitivity response. In vitro uv treatment of parental mouse spleen cells eliminated a graft-versus-host reaction in F₁ recipients as determined by the spleen index. The basis for the differential effect of uv on B and T lymphocyte viability and functional responses is unknown.