Production of suppressor factors induced by ultraviolet irradiation or cis-urocanic acid requires Lyt2+ lymphocytes

Both ultraviolet (UV) irradiation and cis-urocanic acid (UCA) are reported to be associated with the suppression of contact hypersensitivity (CHS) and the induction of a soluble factor which suppresses leukocyte adherence inhibition (LAI) assays in vitro. The cellular origin of the suppressor factor (SF) has now been investigated in vivo and in vitro, using monoclonal antibodies against lymphocyte surface markers to deplete certain cell populations, namely T lymphocytes bearing the L3T4 (helper) and Lyt-2 (suppressor) markers. Depletion of Lyt-2 cells from irradiated mice in vivo and from spleen cell cultures in vitro led to the elimination of detectable levels of SF. Depletion of L3T4 cells had no such effect. Similarly, Lyt-2 cells (but not L3T4 cells) were shown to be necessary for the production of SF by normal spleen cells cultured with cis-UCA. These data suggest that the production of SF following UV irradiation may be related to the action of cis-UCA on Lyg-2 lymphocytes