Dataset Information

MICA diversity and linkage disequilibrium with HLA-B alleles in renal-transplant candidates in southern Brazil.

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.

SUBMITTER: Yamakawa RH

PROVIDER: S-EPMC5395226 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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MICA diversity and linkage disequilibrium with HLA-B alleles in renal-transplant candidates in southern Brazil.

Yamakawa Roger Haruki RH Saito Patrícia Keiko PK Gelmini Geórgia Fernanda GF da Silva José Samuel JS Bicalho Maria da Graça MDG Borelli Sueli Donizete SD

PloS one 20170418 4

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 re ...[more]

PMID: 28419176

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Project description:Immunosuppression is needed in HLA identical sibling renal transplantation. We conducted a tolerance trial in this patient cohort using Alemtuzumab induction, donor hematopoietic stem cells, tacrolimus/mycophenolate immunosuppression converted to sirolimus, planning complete drug withdrawal by 24 months post-transplantation. After an additional 12 months with no immunosuppression, normal biopsies and renal function, recipients were considered tolerant. Twenty recipients were enrolled. Of the first 10 (>36 months post-transplantation), 5 had immunosuppression successfully withdrawn for 16-36 months (tolerant), 2 had disease recurrence and 3 had subclinical rejection in protocol biopsies (non-tolerant). Microchimerism disappeared after 1 year, and CD4+CD25highCD127-FOXP3+ T cells and CD19+IgD/M+CD27- B cells increased to 5 years post-transplantation in both groups, whereas immune/inflammatory gene expression pathways in the peripheral blood and urine were differentially downregulated in tolerant compared to non-tolerant recipients. Therefore, in this HLA identical renal transplant tolerance trial, absent chimerism, Treg and Breg immunophenotypes were indistinguishable between tolerant and non-tolerant recipients, but global genomic changes indicating immunomodulation were observed only in tolerant recipients. A total of 46 PBMC samples representing blood draws from four time points in the first 9 recipients were processed for microarray analysis (The Scripps Research Institute, La Jolla, CA). The analyzed time points were: immediately pre-operatively in the absence of immunosuppression (n=9); post-operatively at 1 year (n=8, range 11-13 months); at 2 years (n=12, range 18-25 months); >3 years (n=17, range 32-48 months). (At year 2 and at > 3 years, repeated samples were obtained from individual subjects, and at one year, one subject had a technically unsatisfactory sample.) To discount the effects of immunosuppression on gene expression, microarray data were included on whole blood from 18 healthy human subjects (controls: GSE40586; NCBI Gene Expression Omnibus [GEO] repository).

Project description:BackgroundHLA molecular mismatch (MM) is a risk factor for de novo donor-specific antibody (dnDSA) development in solid organ transplantation. HLA expression differences have also been associated with adverse outcomes in hematopoietic cell transplantation. We sought to study both MM and expression in assessing dnDSA risk.MethodsOne hundred three HLA-DP-mismatched solid organ transplantation pairs were retrospectively analyzed. MM was computed using amino acids (aa), eplets, and, supplementarily, Grantham/Epstein scores. DPB1 alleles were classified as rs9277534-A (low-expression) or rs9277534-G (high-expression) linked. To determine the associations between risk factors and dnDSA, logistic regression, linkage disequilibrium (LD), and population-based analyses were performed.ResultsA high-risk AA:GX (recipient:donor) expression combination (X = A or G) demonstrated strong association with HLA-DP dnDSA (P = 0.001). MM was also associated with HLA-DP dnDSA when evaluated by itself (eplet P = 0.007, aa P = 0.003, Grantham P = 0.005, Epstein P = 0.004). When attempting to determine the relative individual effects of the risk factors in multivariable analysis, only AA:GX expression status retained a strong association (relative risk = 18.6, P = 0.007 with eplet; relative risk = 15.8, P = 0.02 with aa), while MM was no longer significant (eplet P = 0.56, aa P = 0.51). Importantly, these risk factors are correlated, due to LD between the expression-tagging single-nucleotide polymorphism and polymorphisms along HLA-DPB1.ConclusionsThe MM and expression risk factors each appear to be strong predictors of HLA-DP dnDSA and to possess clinical utility; however, these two risk factors are closely correlated. These metrics may represent distinct ways of characterizing a common overlapping dnDSA risk profile, but they are not independent. Further, we demonstrate the importance and detailed implications of LD effects in dnDSA risk assessment and possibly transplantation overall.

Dataset Information

MICA diversity and linkage disequilibrium with HLA-B alleles in renal-transplant candidates in southern Brazil.

Publications

MICA diversity and linkage disequilibrium with HLA-B alleles in renal-transplant candidates in southern Brazil.

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