Characterization of immunoregulatory T cells during pregnancy by monoclonal antibodies.

T Lymphocyte subpopulations were characterized by means of monoclonal antibodies in 44 pregnant women at different stages of gestation, and in 45 healthy controls. In the pregnant subjects, there is a small but significant reduction of the whole circulating T Lymphocytes and of their T helper subset identified respectively by OKT3 and OKT4 monoclonal antibodies. There is no influence of pregnancy on the proportions of T cytotoxic-suppressor cells (OKT8 positive) nor of lymphocytes bearing Ia antigen. Low counts of circulating cells with a thymocyte phenotype (OKT6 positive) are found in the two groups of subjects. It is concluded that pregnancy has a marginal effect on maternal immunocompetence.