ALLOIMMUNIZATION AGAINST WELL-DEFINED POLYMORPHIC MAJOR HISTOCOMPATIBILITY OR CLASS-I MHC TRANSFECTED L-CELLS ANTIGENS CAN PREVENT POLY-I-CINDUCED FETAL DEATH IN MICE

METHOD: It is possible to induce increased fetal resorption in a numbe r of inbred murine matings by injecting Poly (I) Poly (C12U) 3.5 days postconception, a maneuver associated with natural killer-mediated dam age to the fete placental unit such as occurs in spontaneous fetal res orptions. RESULTS: We show here that alloimmunization can block this e ffect. In addition, maternal immune responses induced by alloimmunizat ion against isolated mutant class I or class II, as well as by immuniz ation with class I MHC alloantigens (K-d) transfected L cells are suff icient to restore normal fetal viability. It is not necessary that the maternal immune response be specifically directed against paternal al loantigens fr the fetal protecton to ensue, since the effect occurs in inbred matings when the mother is immunized against unrelated class I or class II alloantigens. As in previous studies conducted in the mur ine species, not all MHC alloimmunizations are protective. In addition , as control, immunization with a monomorphic class I MHC molecular (3 7), transfected L cells, sheep red blood cells or hen egg lysozyme is without effect. CONCLUSION: These results indicate that defined MHC an tigens can mediate fetal protection from induced fetal resorption, and suggest that one driving force in promoting MHC antigen polymorphism in mammals is their capacity to confer protection from NK mediated fet al demise.