The chorionic villi of term placentas were examined for A and B blood group substance using the IF technique with heterologous and homologous antisera. No specific fluorescence was found in either the villous trophoblast or vessels of the chorionic villi. The implications of these findings in relation to the question of trophoblastic antigenicity are discussed.
SELECTIVE ADVANTAGE OF HETEROZYGOTES AT B BLOOD GROUP LOCUS IN THE CHICKEN