Inhibitory activity of supernatants from murine decidual cell cultures on the mixed lymphocyte reaction

Supernatants from in vitro decidual cell cultures derived from uterine cells of C57BL mice were assessed for immunoregulatory activity by addition at the initiation of a mixed lymphocyte reaction (MLR) between C57BL responder and Balb/c stimulator splenocytes. MLR inhibitory factors were present during two phases of the culture; firstly during decidual cells differentiation and secondly during involution of the culture. These factors were produced whether the cultures were derived from syngeneically or allogeneically mated mice. Addition of supernatants 24 h after the initiation of the MLR also produced an inhibitory effect. Throughout the culture period supernatants also inhibited the control MLR containing C57BL responder and stimulator splenocytes. Peaks of inhibitory material were associated with both high (greater than 1 500) and low (less than 1 500) molecular weight fractions as assessed by Sephadex G15 fractionation. No inhibitory factors were identified in supernatants from similar cultures of embryonic fibroblasts. The results are discussed with respect to the mode of action of these factors and their possible role in the maintenance of the foetal allograft.