HLA-G POLYMORPHISMS AND ALLELE FREQUENCIES IN CAUCASIANS

HLA-G, a nonclassical class I MHC molecule, is uniquely expressed on e xtravillous cytotrophoblasts of the maternal-fetal interface and is su ggested to be essential for establishment of maternal-fetal immune tol erance. Although the level of polymorphism in HLA-G has originally bee n considered low, number, nature and site of polymorphisms seem to var y between different ethnic populations. We investigated HLA-G polymorp hisms in a population of German and Croatian origin by SSCP-analysis a nd direct sequencing as well as RFLP analysis for presence of the 1597 delC mutation. HLA-A alleles associated with the different HLA-G allel es were determined by SSP PCR-typing. In Caucasians, HLA-G exhibits a low degree of polymorphism on the amino-acid level and only slightly h igher variability on the nucleotide level. In 264 independent chromoso mes, 4 HLA-G alleles on the level of amino acid polymorphisms and an a dditional 6 variations of nucleotide sequences could be identified. Th e null-allele G0105N was present at an allele frequency of 2.3% which is higher than initially suggested for Caucasians but lower than in H ispanics and African-Americans. Furthermore, some HLA-G alleles exhibi t strong linkage disequilibrium with HLA-A. (C) American Society for H istocompatibility and Immunogenetics, 1998. Published by Elsevier Scie nce Inc.