Immunological studies of human endometrium--suppression of lymphocyte mitogenesis by endometrial extract.

Immunoregulatory activity that suppresses lymphocyte mitogenesis was demonstrated in human secretory endometrial extracts (SEE). SEE markedly suppressed 3H-thymidine (3H-TdR) incorporation by phytohemagglutinin (PHA)-stimulated lymphocytes compared with myometrial extracts from the same donors. SEE-induced inhibition of lymphocyte response to PHA was significantly (p less than 0.01) greater than that in cultures containing proliferative endometrial extracts at equivalent concentrations. SEE inhibited PHA- and ConA-stimulated cultures much better than PWM cultures, suggesting that it suppressed mitogen stimulation of T cells, but probably not B cells. Investigation of the kinetics of SEE-mediated suppression revealed that it was effective in inhibiting the initial activation processes of T-cell mitogenesis. Preincubation of lymphocytes with SEE followed by washing prevented inhibition of PHA-stimulated proliferation, indicating that the inhibitory effect of SEE might be reversible. The results are discussed with respect to a possible role of the inhibitory factor(s) in SEE in facilitating the implantation process of fetal allograft.