Influence of HLA antigens on reproduction among Japanese population: study of haplotypes in 247 families.

Although an increased incidence of shared HLA antigens among couples experiencing recurrent spontaneous abortion or infertility has been observed, antigenic effects remain to be clarified. These effects, which are suspected to exist among fertile couples, were examined in this study. A group of 247 healthy Japanese families and their 682 children, whose HLA antigen haplotypes could be determined, were studied. Haplotypes of the fathers were compared with those of the mothers, and the combination of HLA antigens in the A, B, C and DR loci was determined as antigenic patterns against the mother. Patterns inherited by children were examined and deviations of the patterns were studied according to the natural rule that either of the haplotypes should be inherited at equal rates. Lower rates of children with antigens common with those of the mother, which may show a result of reproductive selection, were observed among only the first born children in the A (p < 0.05) and DR loci (p < 0.01), but rates similar to those expected were observed among the second born and later children. Lower rates were also observed in the B and C loci among all children with no significant difference between groups of the children. The necessity of differing antigenic factors in order to achieve pregnancy in the population was shown. Important effects of HLA antigenicity in reproductive failure are suggested.