The response of the pregnant ewe to challenge with foetal and paternal lymphocytes.

The efferent lymph from the popliteal lymph nodes of pregnant ewes challenged between 93 and 127 days with specific paternal or foetal lymphocytes was examined. There was an increased efflux of lymphocytes and blast cells from the challenged node, similar to that observed during the response of normal, non-pregnant ewes to allogeneic cells. Additionally, there was a decrease in the mixed lymphocyte and mitogen responsiveness of the efferent lymphatic cells that was comparable with that evoked by challenge of non-pregnant sheep. While cytotoxic cells could not be detected in the lymph after challenge of normal or pregnant animals, specific cytotoxic antibody was invariably produced in both instances. The present observations that the immune responsiveness of the pregnant ewe to foetal lymphocytes remains normal are consistent with an earlier report on the antifoetal reactivity of maternal cells in vitro. It is inferred that the in vitro reactivity of maternal lymphocytes was a valid reflection of the capacity of these cells in the intact ewe.