Effect of sera from immunologically altered mice on phytohemagglutinin-induced mouse lymphocyte transformation.

The DNA-synthetic response of mouse spleen cells to phytohemagglutinin in vitro is depressed by the addition of normal mouse serum. The effects of sera from mice that had been modified immunologically were examined. Increased depressive activity was found in sera from nude mice and from mice recently treated with anti-thymocyte globulin, but no change was found in sera from thymectomized, irradiated, bone marrow-reconstituted mice, nor from lethally or sublethally irradiated or cyclophosphamide-treated mice. Base line DNA synthesis was, however, less inhibited by sera from irradiated or cyclophosphamide-treated mice. Increased depressive activity was found in sera from mice with graft-versus-host reaction and from mice injected with Salmonella enteritidis 11RX, in which macrophage stimulation occurred. Increased depressive activity was also found in the sera of mice injected with sheep erythrocytes. T cells do not appear to be a source of depressive activity but B cells, macrophages and nonlymphoid cells may be sources.