A single dose of UV radiation suppresses delayed type hypersensitivity responses to alloantigens and prolongs heart allograft survival in mice.

The systemic effect of ultraviolet (UV) irradiation on delayed type hypersensitivity (DTH), contact hypersensitivity (CHS) and allograft rejection was investigated in BALB/c mice which had been exposed to a single 1 h treatment with UV radiation (27 kJ/m2) from FS40 sunlamps (60% UVB). After UV irradiation (3-5 days), mice were treated on an unirradiated site with either a subcutaneous injection of allogeneic spleen cells or a topical application of the contact sensitizer oxazolone (OX). The DTH response to allogeneic cells and the CHS response to OX elicited 6 days after immunization were significantly lower in UV-treated mice than in normal mice. Spleen cells from these animals were transferred intravenously into X-irradiated (600R) recipients which were immediately challenged with antigen and the DTH or CHS response elicited was determined 24 h later. Recipients of equal numbers of cells from sensitized and normal animals (6 X 10(6) from each donor) exhibited positive DTH or CHS responses to the antigen used to sensitize the donor. In contrast, recipients of equal numbers of cells from animals sensitized and UV suppressed to the same antigen showed a suppressed DTH or CHS response. This suppression was antigen-specific. Treatment of cells from UV suppressed animals, prior to transfer, with complement and cytotoxic anti-Lyt 2 or anti-Thy 1.2 monoclonal antibodies abrogated the suppressive ability of these cells, in contrast to cytotoxic treatment with anti-L3T4 or anti-Lyt 1 monoclonal antibodies which had no significant effect. The suppressor cells therefore had the phenotype Thy 1.2+, Lyt 2+, L3T4-, Lyt 1-.(ABSTRACT TRUNCATED AT 250 WORDS)