A study of HLA-G polymorphism and linkage disequilibrium in renal transplant patients and their donors Alessandro Pirri a , Fabiana C. Contieri b , Ricardo Benvenutti b , Maria da Graça Bicalho a, ⁎ a Laboratory of Immunogenetics and Histocompatibility—LIGH, Department of Genetics, Universidade Federal do Paraná, Brazil b Hospital Universitário Evangélico de Curitiba, Al Augusto Stellfeld 1908 Curitiba, 80730150, Brazil abstract article info Article history: Received 7 June 2008 Received in revised form 18 September 2008 Accepted 22 September 2008 Keywords: HLA-G Kidney transplantation HLA-A, HLA-DR The role of the Major Histocompatibility Complex (MHC) in transplantation immunology is widely known. Incompatibilities associated with Human Leukocyte Antigens (HLA) between donors and recipients are related to poorer prognosis in allograft acceptance and survival, often resulting in rejection episodes. HLA-A, HLA-B, HLA-DR and HLA-DQ compatibility are widely studied in clinical transplants but few studies investigated the influence of non-classical HLA loci, such as HLA-G, a non-classical class I HLA gene located at 6p21.31 in the MHC region, i.e. 300 kb telomeric to HLA-A. MHC region genes are characterized by extreme polymorphism as well as strong positive linkage disequilibrium (LD) between HLA loci (alleles). LD studies related to MHC region provide investigators with a tool to assess candidate genes with an at-risk HLA haplotype, with implications for allograft transplants, human reproduction and disease susceptibility. Many studies reported striking LD between HLA-G and HLAA alleles and also between HLA-G and HLA Class II alleles, but the biologicalimplications for these findings are not clear yet. DNA sequencing methodology was used to determine HLA-G (exons 2 and 3) polymorphisms from 52 patients who underwent kidney transplantation and their donors. It is the purpose of this study to investigate the influence of HLA-G polymorphism in a set of kidney transplants and the occurrence of rejection episodes. It was observed that pairs with 2 HLA-G matches presented a lower risk of rejection occurrence than those pairs with 0 or 1 match. It was also observed that subjects whose genotype presented one synonymous substitution (S) in one HLA-G allele in the HLA-G⁎0101 group of alleles and another allele with a non-synonymous substitution (N/S) on HLA-G⁎0103, HLA-G⁎010401, HLA-G⁎010403 or HLA-G⁎0105N alleles, apparently had a greater chance of rejection episodes. Additionally, HLA-G, as well as HLA-A, -B e -DR, compatibility may also be important for allograft acceptance (rejection probability lower than 0.09%). Besides, heterozygous S/NS patients had a five times greater chance of rejection than S/S and NS/NS patients. Some haplotypes found in the present study were already described in literature: A⁎01-G⁎01B (⁎010102 or ⁎0106), A⁎03-G⁎0101A, A⁎23-G⁎010401, A⁎26-G⁎01B, A⁎31-G⁎0103, A⁎02-G⁎0101A, A⁎24-G⁎0101A, A⁎33-G⁎0103, A⁎68-G⁎01B. We have also described LD between HLA-G alleles and HLA class II DRB1⁎ allelic groups and found significant LD between DRB1⁎04- G⁎01B, DRB1⁎13-G⁎010401, DRB1⁎14-G⁎010108, DRB1⁎15-G⁎0103, DRB1⁎03-G⁎0101A and DRB1⁎03-G⁎01B. © 2008 Elsevier B.V. All rights reserved. 1. Introduction HLA-G role in transplantation immunobiology began with studies of heart and combined kidney–liver transplants with the purpose of evaluating its expression in these clinical settings. However, recently some studies have investigated HLA-G expression, polymorphism and their relevance to kidney allograft. In addition to its importance in immunology, HLA genes make useful models to investigate gene organization, polymorphisms, linkage disequilibrium (LD), and recom- bination mechanisms [1]. The non-random association of two different (or more) linked loci (haplotypes) has been reported between antigens (phenotypic level) and alleles (genotypic level) in the classical HLA loci. Such allelic combination is not independent and this deviation from independence was termed “linkage disequilibrium”. Regarding the HLA-G locus, several studies reported its association with HLA-A alleles [2–4]. Morales et al. [5] carried out one of the first studies about this association and detected strong LD between alleles of these two loci and demonstrated that different genetic distances could be observed in distinct HLA-A/G haplotypes. LD between HLA-A/G alleles is similar to that observed between some of the class II loci, such as HLA- DR/DQ alleles, where recombination, due to strong linkage has yet to be directly observed [6]. By analogy, one can presume that recombination in between HLA-A/G alleles present in these loci is a rare event. Suppression of recombination is facilitated by deletion of approximately Transplant Immunology 20 (2009) 143–149 ⁎ Corresponding author. Universidade Federal do Paraná Laboratory of Immunoge- netics and Histocompatibility, Department of Genetics, R. Cel. Francisco H. dos Santos S/ N. Centro Politécnico-Jardim das Américas, CP 19071, CEP 81.530.990, Curitiba, Brazil. Tel.: +55 41 33611729; fax: +55 41 3266 2042. E-mail address: ligh@ufpr.br (M.G. Bicalho). 0966-3274/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.trim.2008.09.012 Contents lists available at ScienceDirect Transplant Immunology journal homepage: www.elsevier.com/locate/trim