Circulating suppressor factors in mice subjected to ultraviolet irradiation and contact sensitization.

BALB/c mice subjected to a single dose of UV-B radiation showed suppressed contact hypersensitivity to trinitrochlorobenzene. The in vitro antigen reactivity of peritoneal cells from these mice was investigated using the leucocyte-adherence inhibition assay. These cells showed a high degree of reactivity with specific antigen. However, this reactivity, but not the reactivity of cells from non-irradiated sensitized mice, could be suppressed by serum from UV-treated sensitized mice. The suppressive effect of this serum could also be demonstrated on other syngeneic systems with unrelated antigens and was partially effective with allogeneic cells, indicating a lack of antigen specificity and genetic restriction. Suppressive properties were also found in serum taken from mice 3-5 days (but not at other times) after irradiation without subsequent sensitization.