ANOMALOUS INHERITANCE OF A PATERNALLY DERIVED TROPHOBLAST ANTIGEN

PROBLEM: Recurrent spontaneous abortion occurs in 1 in 500 random mati ngs and usually results in abortion of all pregnancies. If absence of antibody to a paternally derived antigen caused abortion, the woman wo uld be expected to make antibody to the other paternal antigen and abo rt only half her pregnancies. METHODS: Microvesicles were prepared fro m equine placentae. Acid-eluted IgG antibody was eluted from the polym orphic R80K antigen and used to type the residual R80K antigen on vesi cles or on peripheral blood leucocytes. RESULTS: In several equine sib ships all the half-sibs had the same paternal R80K alloantigen. In the extended horse family descended from the stallion Nearco, three allot ypes were found. The allele present was usually the grandpaternal one, but exceptions are seen. Whichever allele is transmitted all the prog eny have the same alloantigen (probability of this occurring by chance = 2(-45)). CONCLUSION: Because only one paternal allotype is present in all progeny, lack of antibody to the R80K antigen would result in l oss of all pregnancies, not one half.