ANTIBODY-RESPONSE OF EWES AND DOES TO CHIMERIC SHEEP-GOAT PREGNANCY

Antibody production was evaluated in 62 recipients of blastomere-aggre gation sheep-goat embryos, including 23 multiparous ewes, 21 multiparo us does, 16 primiparous does, and 2 virgin does. The reactivity of ser a collected weekly after the embryo transfer surgery was compared to t hat of sera collected prior to the embryo transfer by means of 1) comp lement-dependent cytotoxicity tests against peripheral blood lymphocyt es (PBLs) from the parents of the embryo(s) 2nd from random-bred sheep and goats, 2) hemagglutination and hemolytic assays with red blood ce lls (RBCs) from the two sires of the embryo(s), and 3) assays with PBL s and RBCs following absorptions with RBCs and PBLs from the parents a nd offspring. Although cross-reactivity to ovine and caprine PBL antig ens was present in the control sera of some recipients, xenogeneic imm unization during pregnancy was detected in 20 of 30 recipients that ex perienced term pregnancy. The xenogeneic response involved the product ion of antibody that reacted with both PBLs and RBCs. Allogeneic respo nses to RBCs were not observed, but allogeneic responses to PBLs occur red frequently, beginning after the onset of the xenogeneic response i n most recipients (98 +/- 28 vs. 57 +/- 15 days in ewes; 93 +/- 23 vs. 46 +/- 7 days in does; mean day of onset +/- SD). The onsets of the r esponses were examined in conjunction with data collected on fetal and placental chimerism to evaluate possible routes of immunization. The onsets of the allogeneic responses and the limited serum reactivity to third-party PBLs suggested that fetal lymphocytes leaking across the placenta immunized the recipients to parentally inherited polymorphic antigens. The xenogeneic responses were associated with placental chim erism and appeared to involve the recognition of a species-specific mo nomorphic antigen shared by PBLs and RBCs. Neither of the responses ap peared to affect continuation of pregnancy to term.