5′ and 3′ untranslated regions contribute to the differential expression of specific HLA‐A alleles

Abstract

In hematopoietic stem cell transplantation (HSCT), when no HLA full-matched donor is available, alternative donors could include one HLA-mismatched donor. Recently, the low expressed HLA-C alleles have been identified as permissive mismatches for the best donor choice. Concerning HLA-A, the degree of variability of expression is poorly understood. Here, we evaluated HLA-A expression in healthy individuals carrying HLA-A*02 allele in different genotypes using flow cytometry and allele-specific quantitative RT-PCR. While an interindividual variability of HLA-A*02 cell surface expression, not due to the allele associated, was observed, no difference of the mRNA expression level was shown, suggesting the involvement of the posttranscriptional regulation. The results of qRT-PCR analyses exhibit a differential expression of HLA-A alleles with HLA-A*02 as the strongest expressed allele independently of the second allele. The associated non-HLA-A*02 alleles were differentially expressed, particularly the HLA-A*31 and HLA-A*33 alleles (strong expression) and the HLA-A*29 (low expression). The presence of specific polymorphisms in the 5 and 3 untranslated regions of the HLA-A*31 and HLA-A*33 alleles could contribute to this high level of expression. As previously described for HLA-C, low-expressed HLA-A alleles, such as HLA-A*29, could be considered as a permissive mismatch, although this needs to be confirmed by clinical studies.Keywords: Allele · Expression · HLA · Hematopoietic stem cell transplantation · Polymorphism Additional supporting information may be found in the online version of this article at the publisher's web-site IntroductionHematopoietic stem cell transplantation (HSCT) is now widely used for the treatment of high-risk hematological malignancies, such as acute leukemia. To find a suitable donor, human leukocyte antigen (HLA) typing is performed. In most transplant Correspondence: Dr. Céline René e-mail: celine.rene@inserm.fr centers, a perfect match (10/10) of the ten alleles of the HLA-A, -B, -C, -DQB1, and -DRB1 loci is considered to be the optimal condition for HSCT with unrelated living donors. However, this requirement is fulfilled in just about half of the HSCTs, despite the expansion of international donor registries [1]. For patients lacking HLA-matched unrelated donors, single HLA * These authors contributed equally to this work.www.eji-journal.eu Eur. J. Immunol. 2015. 45: 3454-3463 Molecular immunology 3455 mismatch unrelated donors might be considered as alternative donors. However, the risk of graft versus host disease (GVHD) is increased and overall survival is reduced in patients who receive a graft from a donor with a single mismatch in the HLA class I locus compared with the HLA-matched situation [2,3]. Moreover, the adverse effects on the patient's outcome depend also on the locus carrying the mismatch between donor and recipient [4,5]. In this context, in order to increase the safety of HSCT with HLA-mismatched unrelated donors, a better understanding of the factors that trigger t...

Quantification of classical HLA class I mRNA by allele‐specific, real‐time polymerase chain reaction for most Han individuals

“…In addition, the molecular mechanism underlying HLA expression regulation at the allelic level is far from clear. Although potential mechanisms underlying the regulation of allelic expression at the transcriptional level have been indicated, contradictory conclusions were reached in these studies. To examine how HLA alleles are regulated, analysis of the mRNA level of each allele is essential.…”

“…It has been confirmed that the expression levels of different alleles on the same HLA class I locus can vary dramatically . This differential HLA expression according to alleles could have a broad clinical impact, such as influencing virus infection control, risk of autoimmune disorders, and haematopoietic stem cell transplantation (HSCT) outcomes .…”

“…This locus‐specific PCR amplifies both alleles of the locus, leaving the expression level of each allele unknown. Recently, real‐time PCR assays aimed at amplifying given allotypes or alleles were developed in a few studies . However, no systematic method has been established to quantify HLA class I mRNA at the allelic expression level for most individuals in any population.…”

Killer Immunoglobulin-Like Receptor Allele Determination Using Next-Generation Sequencing Technology

“…A link between KIR allelic polymorphism and the expression level and/or function of the corresponding KIR + NK cells is necessary for all KIR genes as previously established for the expression level of HLA-A and HLA-Cw molecules (54–56). We speculate that KIR allelic polymorphisms may affect not only the distribution and function of these gene products but also the licensing of NK subpopulations as described for HLA class I molecules (57, 58).…”

Allorecognition of HLA-C Mismatches by CD8+ T Cells in Hematopoietic Stem Cell Transplantation Is a Complex Interplay between Mismatched Peptide-Binding Region Residues, HLA-C Expression, and HLA-DPB1 Disparities

“…Several studies have recently reported variability in the expression of different HLA-C serotypes, as determined at the cell surface or mRNA steady-state levels (5–8). Variability within HLA-A serotypes has also been recently reported (9). A search for genetic markers of HLA-C expression led to the description of two relevant polymorphisms.…”