Studies on mitogen-induced lymphocyte transformation and the effect of pregnancy serum on mitogen-induced normal...

It is recognised that there is a non-reactive status in the maternal immune system during normal pregnancy as it fails to recognise the fetus which is an allograft. The present study was aimed to understand the nature of cell-mediated immune response and the presence of immunosuppressive factors during human pregnancy. The functional reactivity of lymphocytes was found to be reduced during pregnancy, particularly in the third trimester, as phytohaemagglutinin- and concanavalin-A-induced lymphocyte transformation was affected. It was also observed that in primigravidae and pregnant women with a history of repeated abortions the lymphocyte reactivity was not reduced during the first and second trimesters, but there was a marked reduction in the third trimester. However, in the case of multigravidae there was no change in lymphocyte transformation between the trimesters. When pregnancy serum from various trimesters was tested for its suppressive activity, it was found to suppress the mitogen-induced proliferation of lymphocytes from normal donors. Sera from primigravidae and patients with a history of abortion showed the highest suppressive activity in the third trimester, whereas sera from multigravidae showed high suppression in all the trimesters.