POSSIBLE SEX-CORRELATED TRANSMISSION OF MATERNAL CLASS-I HLA HAPLOTYPES

Forty-seven alleles of class I HLA-AB loci (14 for locus A and 33 for locus B) were identified in 787 participants in two groups of unrelate d families. Group I included parents and children typed for bone marro w transplantation. Group II included families typed for renal transpla ntation. Before statistical evaluation, the A locus alleles were group ed into eight classes according to broad specificity, and the B locus alleles were grouped according to HLA epitopes into two classes. Signi ficant differences in KLA-AB haplotype frequencies were found between male and female offspring. When families with children of both sexes w ere analysed, the frequencies of maternally inherited HLA-AB haplotype s were found to be significantly different in brothers and sisters. Th e results suggest the possibility that the transmission of specific AB haplotypes from mother to offspring may be correlated to children's s ex. The major histocompatibility complex has been shown to be involved in the expression of H-Y male-specific minor histocompatibility antig ens. The possible selection in the transmission of specific maternal H LA-AB haplotypes to male offspring may contribute to the avoidance of maternal cytotoxic reactions toward the male foetus.