FUNCTIONAL AND BIOCHEMICAL-PROPERTIES OF A MOUSE PLACENTAL IMMUNOREGULATORY FACTOR

The authors have a long standing interest in immune regulations which control the absence of rejection of a semi-allogeneic fetus by the mot her. A previous work described a soluble 40 kDa factor extracted from mouse placenta and capable of inhibiting secondary immune responses in vivo. The present paper reports the following on its mode of action i n vivo: (1) it is active even in a fully allogeneic host; (2) it can b e administered i.v. or i.p. along with antigen; and (3) the injections of factor and antigen must not be more than 2 days apart for maximum efficacy. Moreover, the results of the study described here indicate a lso that this factor is a concanavalin A-binding glycoprotein, sensiti ve to heat and pronase, and different from interleukin 10 (IL-10). Thu s, this placental factor appears to be different from previously descr ibed immune regulators such as IL-10 and could contribute significantl y to immune regulations at the level of the placenta.