Abstract
The major histocompatibility complex (MHC) class I chain-related gene A (MICA) is located centromerically to the human leukocyte antigen (HLA)-B. The short distance between these loci in the MHC indicates the presence of linkage disequilibrium (LD). Similarly to the HLA, the MICA is highly polymorphic, and this polymorphism has not been well documented in different populations. In this study, we estimated the allelic frequencies of MICA and the linkage disequilibrium with HLA-B alleles in 346 renal-transplant candidates in southern Brazil. MICA and HLA were typed using the polymerase chain reaction-sequence-specific primer method (PCR-SSO), combined with the Luminex technology. A total of 19 MICA allele groups were identified. The most frequent allele groups were MICA*008 (21.6%), MICA*002 (17.0%) and MICA*004 (14.8%). The most common haplotypes were MICA*009-B*51 (7.8%), MICA*004-B*44 (6.06%) and MICA*002-B*35 (5.63%). As expected from the proximity of the MICA and HLA-B loci, most haplotypes showed strong LD. Renal patients and healthy subjects in the same region of Brazil showed statistically significant differences in their MICA polymorphisms. The MICA*027 allele group was more frequent in renal patients (Pc = 0.018, OR: 3.421, 95% CI: 1.516–7.722), while the MICA*019 allele group was more frequent in healthy subjects (Pc = 0.001, OR: 0.027, 95% CI: 0.002–0.469). This study provided information on the distribution of MICA polymorphisms and linkage disequilibrium with HLA-B alleles in Brazilian renal-transplant candidates. This information should help to determine the mechanisms of susceptibility to different diseases in patients with chronic kidney disease, and to elucidate the mechanisms involved in allograft rejection associated with MICA polymorphisms in a Brazilian population.
Highlights
The major histocompatibility complex (MHC) class I chain-related gene A (MICA) is one of the highly polymorphic genes located in the human MHC [1,2,3] and is located 46 kb centromerically from the human leukocyte antigen (HLA)-B
Previous studies have reported some ethnic differences in the distribution of MICA polymorphisms, similar to those found for HLA polymorphisms [16,17,18]
The MICA and HLA-B allelic frequencies are shown in Tables 1 and 2, respectively
Summary
The major histocompatibility complex (MHC) class I chain-related gene A (MICA) is one of the highly polymorphic genes located in the human MHC [1,2,3] and is located 46 kb centromerically from the human leukocyte antigen (HLA)-B. To the known involvement of preformed antibodies against the HLA antigens in acute and chronic rejection of a graft [8, 10,11,12], many studies have shown the importance of MICA alloantibodies in the rejection of various organs [13, 14]. Previous studies have reported some ethnic differences in the distribution of MICA polymorphisms, similar to those found for HLA polymorphisms [16,17,18]. MICA polymorphisms in different populations have not been as well documented as those of HLA. No studies in Brazil have investigated the MICA allelic diversity and linkage disequilibrium with HLA-B in renal-transplant candidates
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