Effects of maternal preimmunization on the decidual cell reaction in mice

Maternal immunological recognition mechanisms during pregnancy

One of the most intriguing shortcomings of modern immunology, especially transplantation immunology, is its failure to provide a satisfactory final explanation for the consistent non-rejection of immunogenetically alien conceptuses in utero, even in specifically preimmunized females. Certainly, there is no shortage of hypotheses. Over the past few years various observations have utterly refuted the simplistic notion that the much-mated but nulliparous or gravid females are immunologically unaware of the presence and activities of allogeneic cells transiently or chronically within their reproductive tracts. This evidence has engendered the belief that some kind(s) of active response(s) on the part of the female, following early recognitive events, plays an important, if not essential, role, in conjunction with adaptive hypoantigenicity of the trophoblast, not only in conferring selective benefits upon the conceptus from the time of implantation, but also in affording it protection from the possible hazards of a cellular immunity. Evidence is emerging that during mating, implantation, placentation, and gestation (1) various fetal and histocompabibility antigens are presented to the mother in a unique manner; (2) she does respond to these; and (3) her responses aid in the establishment and maintenance of a harmonious state of immunological coexistence with her fetus. There are reasonable grounds for believing that a complete understanding of the immunobiology of the maternal-fetal relationship may facilitate significant advances in both transplantation and tumour immunology.

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.

Evidence for the role of the maternal immune system in balancing the sex ratio in mice

Two experiments have been conducted to verify the effect of maternal preimmunization to H-Y antigen on the secondary sex ratio in C57Bl/6 mice. In accord with the theoretical model previously proposed, it was found that extensive immunization to H-Y antigen following splenectomy resulted in a significant increase in sex ratio (males/females) without affecting litter size. Litter size was also not correlated to sex ratio. The data from both experiments suggest that splenectomy alone or restimulation to H-Y antigen (after 30 days) both act to decrease sex ratio. It is concluded that the maternal immune system plays a limited, but significant, role in maintaining the normal sex ratio in mice.