• Abortion;
  • HLA;
  • HLA class I;
  • natural killer cells;
  • pregnancy;
  • recurrent spontaneous abortion

PROBLEM: Human leukocyte antigen (HLA)-C and possibly also HLA-B seem to be expressed on the extravillous trophoblast. These antigens carry epitopes that function as ligands for natural killer (NK)-cell-inhibitory receptors. Antitrophoblast cytotoxicity mediated by decidual NK cells might be involved in miscarriage. We thus found it relevant to elucidate whether parental HLA-C and -Bw polymorphism play a role in recurrent miscarriage (RM).

METHOD OF STUDY: HLA-C and -Bw investigations by DNA-based techniques were undertaken in 35 couples with unexplained RM and in 30 couples with normal fecundity. The number of HLA-C- and -Bw-related supertypic specificities that can bind NK-cell-inhibitory receptors was evaluated in selected couples.

RESULTS: The proportions of couples with RM and control couples carrying four HLA-C alleles with the same NK-cell-inhibitory supertypic specificities were equal. In 46% of studied couples with RM, all four HLA-B alleles carried the HLA-Bw6 supertypic specificity, which was significantly higher than the corresponding frequency (17%) in the control couples (P < 0.02).

CONCLUSIONS: The expression of polymorphic HLA-C on trophoblasts does not seem to play a role in RM. Assuming that HLA-B is expressed on trophoblasts, we may suggest that the revealed predominance of HLA-Bw6 expression (which excludes the presence of HLA-Bw4—protective antigens) may predispose a particular couple to the RM phenomenon.