Immunological responsiveness of maternal and foetal lymphocytes during normal pregnancy in the ewe

Peripheral blood lymphocytes collected from ewes before and during pregnancy manifested constant reactivity to concanavalin A and to paternal and third party peripheral blood lymphocytes. However, in some instances, the reactivity of these maternal cells against lipopolysaccharide and lymphatic lymphocytes from paternal, foetal and third-party donors increased markedly during pregnancy. Apart from an indication that plasma from some pregnant ewes acquired the capacity to depress lymphocyte reactivity non-specifically, no evidence was obtained to suggest that maternal lymphocyte reactivity observed in vitro did not accurately reflect the capacity of these cells in the donor ewe. In particular, there was no indication that populations of maternal peripheral blood lymphocytes returning from the gravid uterus had undergone any modification of reactivity against foetal determinants.