HLA-G POLYMORPHISMS - ETHNIC-DIFFERENCES AND IMPLICATIONS FOR POTENTIAL MOLECULE FUNCTION

PROBLEM: Human leukocyte antigen (HLA)-G is uniquely expressed on extr avillous cytotrophoblasts of the placenta and is postulated to be a me diator of maternal immune tolerance. Although it was originally consid ered to be nonpolymorphic, Variations of the HLA-G DNA sequence have b een reported, and a limited number of HLA-G alleles been defined. METH OD OF STUDY: The HLA-G wild-type sequence was compared with HLA-A2 wit h regard to the conservation of functionally essential parts of classi cal HLA-I molecules. HLA-G polymorphisms were analyzed under the aspec t of ethnic differences, site, and consequences for postulated molecul e functions. RESULTS: HLA-G exhibits a high degree of conservation rel ative to HLA-A2 in functionally relevant sites of HLA-class I molecule s. However, polymorphic sites in HLA-G and classical HLA loci are not congruent. CONCLUSION: The type and localization of HLA-G polymorphism s suggest that different parts of the HLA-G molecule underlie differen t selective constraints.