The relationship between pregnancy, HCS and B lymphocytes.

The quantitative distribution of the lymphocyte subpopulations (B, T and null) and the serum concentrations of Human Chorionic Somatomammotropin (HCS), immunoglobulins IgG, IgM and IgA, complement component C4 and C1 inactivator, were estimated in venous blood samples from 32 women at various stages of pregnancy and compared with a control series of 7 non-pregnant normal women. A significant decline in the B cell percentage during pregnancy was seen. The fall in the percentage of the B lymphocytes was found to be concomitant with the rise in HCS concentration. No significant changes in the other parameters studied were present.