Linkage disequilibria between human leucocyte antigen-B and closely linked microsatellites in the Croatian population

The aim of the present study was to investigate polymorphism of D6S2927, STR_MICA, D6S2793, TNFa (D6S2792), TNFb and TNFd (D6S2789) microsatellites and linkage disequilibria between these loci and human leucocyte antigen (HLA)‐B (previously tested) for better characterisation of extended HLA haplotypes. A total of 176 healthy unrelated Croatians were studied using polymerase chain reaction amplification and electrophoresis on 6% polyacrylamide gel in ALFexpress sequencer. Eight HLA‐B/D6S2927 haplotypic associations (B*07/D6S2927‐4, B*08/D6S2927‐3, B*18/D6S2927‐3, B*27/D6S2927‐1, B*35/D6S2927‐5, B*38/D6S2927‐4, B*51/D6S2927‐2 and B*61/D6S2927‐1) showed strong association (P < 0.001, D > 0.5). Among 88 different HLA‐B/STR_MICA haplotypic associations, seven combinations (B*07/STR_MICA‐A5.1, B*08/STR_MICA‐A5.1, B*15/STR_MICA‐A5, B*18/STR_MICA‐A4, B*27/STR_MICA‐A4, B*38/STR_MICA‐A9 and B*51/STR_MICA‐A6) demonstrated high linkage (D≥ 0.3) with significant P value (P < 0.001). Strong associations were also observed for five HLA‐B/D6S2793 haplotypes (B*07/D6S2793‐CA17, B*08/D6S2793‐CA24, B*13/D6S2793‐CA18, B*14/D6S2793‐CA14 and B*27/D6S2793‐CA14). HLA‐B*08/TNFb3 and HLA‐B*50/TNFb7 were the strongest associations for HLA‐B/TNFb. Nine HLA‐B/TNFa combinations were observed with significant P value (B*07/TNFa11, B*08/TNFa2, B*13/TNFa7, B*18/TNFa10, B*27/TNFa6, B*37/TNFa9, B*38/TNFa10, B*39/TNFa13 and B*44/TNFa4). Out of six HLA‐B/TNFd haplotypic associations with strong D value, HLA‐B*08/TNFd2 and B*37/TNFd3 showed the highest statistical significance (P < 0.0001). These results provide data on the region around the HLA‐B that is very attractive because of its contribution to genetic susceptibility for many HLA‐associated diseases and therefore this information will help in all further HLA‐B locus–associated disease studies.