The aim of the present study was to compare
haplotypes of the most frequent B*27
alleles among Croatians (B*2702 and *2705) and the rare B*2730
allele. For this purpose, 37 families with members carrying
human leukocyte antigen (HLA)-B27 were
selected. All individuals were analysed for eight
microsatellites (Msats): D6S2927,
short tandem repeat - MHC class I-related gene (STR_MICA), D6S2793, D6S2811,
tumor necrosis factor a (
TNFa),
tumor necrosis factor d (TNFd), D6S273 and D6S1014, while individuals carrying the
HLA-B27 specificity were subtyped. Of 39 analysed
haplotypes, 20 individuals had B*2702, 15 subjects were positive for the B*2705
allele, the B*2730
allele was found in three
haplotypes from different families, while one individual carried the B*2703
allele.
HLA-A3 and -DRB1*16 were shared by all three B*2730
haplotypes. The DRB1*16
allele was also observed in the majority of B*2702
haplotypes (76.5%), while
HLA-A3 was, after
HLA-A2, the second most frequent
HLA-A specificity in B*2702
haplotypes. No such
correlation was found for the B*2705
haplotypes. Msat analysis showed that B*2730
haplotypes also share the same
allele at all tested Msats. The D6S2927, D6S2793, MICA and TNFd Msats were not useful in distinguishing B*2702 and B*2705
alleles because D6S2927-213bp, STR_MICA-179bp, D6S2793-206bp, D6S2811-83bp and TNFd-130bp were detected in almost all cases. Conversely, for the
TNFa, D6S273 and D6S1014 loci,
haplotypes carrying B*2702 and B*2730 shared a single Msat
allele in the majority of cases (TNFa-113bp, D6S1014-134bp and D6S273-134bp), which was not observed for B*2705
haplotypes. In conclusion, the similarity between B*2702 and B*2730
DNA sequences as well as their sharing of the same haplotypic combinations corroborates the proposed mechanism of B*2730 evolution from B*2702 by interallelic recombination.
