Lymphocyte reactivity to mitogens and natural killer cell activity in crossbred swine during the reproductive cycle.

The effect of pregnancy and lactation on the cell-mediated immune response of first litter gilts was assessed using the response of circulating lymphocytes to in vitro mitogen stimulation and the cytotoxic activity of the circulating natural killer (NK) cells. Groups of gilts were sampled during the first, second and third trimester of gestation, weekly during lactation, at weaning and estrus following weaning of the piglets. No significant differences were found in the response of the cells from any of the groups to phytohemagglutinin A or concanavalin A stimulation. The natural killer cell activity, measured as cytotoxicity, decreased during gestation reaching a low point during the second and third week of lactation.