Analysis of serum-mediated immunosuppression in normal pregnancy, abortion and contraception.

Blood samples were obtained from pregnant women, threatened pregnancies, abortions, from women taking oral contraceptive drugs and normal controls. The measurement of immunoglobulins, G, A, M and E was done in all samples. The mean levels were normal in all cases, excepting the IgG levels which in normal pregnancies were decreased. Analysing the effect of these sera on the "in vitro' response of peripheral blood lymphocytes to PHA, a strong inhibition could be observed with the serum of normal pregnant women, with that of aborted pregnancies, that of women taking oral contraceptives and to a lesser extent with that of threatened pregnancies. Abortion experiments demonstrate that a large part of this inhibitory effect was attributable to the PZP factor. On the other hand, inhibitory sera failed to inhibit the "in vitro' production of MIF or the capacity of lymphocytes to form E-rosettes. A specific effect of PZP on the release of mitogenic factor by stimulated lymphocytes is suggested.