Phytohemagglutinin response of murine spleen cells during pregnancy and inhibition of normal phytohemagglutinin response by pregnancy or post-partum serum.

The in vitro blastogenic response of spleen cells to phytohemagglutinin-M (PHA) was evaluated as a measurement of the immunologic reactivity of virgin, pregnant and post-partum mice. In PHA-stimulated cultures 3H-thymidine incorporation by lymphocytes from post-partum mice was not significantly different from that of virgin age-matched control mice. Background 3H-thymidine incorporation was high in cultures from post-partum mice resulting in stimulation indices which were lower than those of virgin controls. Spleen cells from mice sacrificed after various intervals of pregnancy showed depressed PHA responsiveness only at the 15th day of gestation. The PHA response of normal spleen cells was depressed in the presence of serum from pregnant or post-partum mice.