Immunological reactivity of maternal lymphocytes during normal pregnancy in the rat.

Thoracic duct lymphocytes from pregnant PVG rats differed markedly from similar cells collected from non-pregnant donors in their reactivity in popliteal lymph node assays performed in (PVG x DA) F1 hybrid hosts. Cells from pregnant rats failed to evoke an increase in popliteal node size commensurate with higher challenge doses of lymphocytes. This modification in maternal lymphocyte reactivity was not dependent on the presence of foetuses genetically compatible with the F1 hybrid rats used in the popliteal lymph node assay. The mechanism responsible for the decrease in size of responding F1 hybrid popliteal lymph nodes appeared to be based on a reduced capacity of lymphocytes from pregnant donors to stimulate a response by host lymphocytes.