Regulatory T-cell subpopulations in pregnancy. II. Evidence for suppressive activity of the late phase of MLR.

Adding mitomycin-treated spleen cells from an allopregnant mouse to a material-strain cells v. paternal-strain cells MLR was previously shown to decrease the intensity of the reaction, due to suppressor T cells. In the present study, spleen cells from allogeneically pregnant mice, were added without treatment at day 2 of an MLR of maternal strain responder cells raised against paternal-strain stimulators. It was shown that, while, on 2 day duration culture versus the same stimulator cells these cells are hyper-reactive compared to controls, yet they lead to a MLR of lower intensity than when the same operation was performed with control cells. This suppressive effect is T-cell dependent and use of high dilutions of anti-Thy 1+C suggests that the suppressor cell has a high density of Thy 1 surface antigen. Involvement of these cells in negative regulation of the late phase of the MLR is suggested. MLRs with cells from allopregnant mice as responders were themselves susceptible to this suppression and even more so than cells from virgin mice, indicating a possible physiological role.