Influence of pregnancy on the immune response to ragweed antigen in rats.

The reactivity of spleen lymphocytes in culture and the reaginic antibody (IgE) response to nondialyzable water-soluble ragweed (DWSR) extract were assessed at different intervals of pregnancy in rats. On day 6 of pregnancy, spleen cells showed a significant reduction in their mitogenic response to phytohemagglutinin (PHA) and slightly lowered response to concanavalin A (Con A) when compared to that of control nonpregnant rats. On day 11 of pregnancy, values obtained with PHA were slightly lower and those obtained with Con A similar to those of control rats. However, at day 18 of gestation, PHA values also returned to normal levels. In contrast, IgE antibody response to DWSR from day 4 to 9 of pregnancy was either slightly enhanced or similar to that of control rats and significantly suppressed from day 11 to 18 of gestation. The decline in humoral response to DWSR during late pregnancy is discussed in the text.