[Immunocompetent lymphoi- cells from pregnant mice studied in the graft-versus-host reaction].

The capacity of lymphoid cells taken from C57BL/6 mice gravid from the CBA males (the second trimester) to induce the graft-versus-host reaction in the hybrids (CBA X C57B/6) F1 was reduced as compared with the cells of the virgin donors and syngeneic gravid mice. This was expressed by the prolonged survival of the experimental recipients and reduced inhibition of endogenous colony formation in the spleen of the sublethally irradiated (500 r) hybrids. At the end of gravidity this capacity was restored, in some instances even exceeding control figures.