Distribution of MICA alleles and haplotypes associated with HLA-B in Greek population.

INTRODUCTION

The Major Histocompatibility Complex Class I-related chain A gene (MICA) is a highly polymorphic functional gene located close to the HLA-B locus. Certain MICA alleles have been related to inflammatory and autoimmune diseases while MICA antibodies have been implicated in organ allograft rejection or graft-versus-host disease (GVHD).

AIM

The aim of this study was to identify the frequencies of MICA alleles and MICA ~ HLA-B haplotypes in the Greek population since, as far as we know, these data are still limited.

METHODS

DNA was obtained from 277 unrelated healthy Greek individuals of Caucasian origin, volunteer donors of blood stem cells. HLA-B* and MICA* genotyping was performed by reverse PCR-SSOP.

RESULTS

A total of 18 MICA alleles were defined in the present study. The five most frequent alleles in the Greek population were MICA008 (24.6%), MICA009 (22.36%), MICA018 (16.03%), MICA002 (8.02%) and MICA004 (7.17%) which altogether account for 77.8% of all alleles. The most common MICA ~ HLA-B haplotypes were MICA018 ~ B18 (12.5%) and MICA009 ~ B*51(11.5%).

CONCLUSIONS

The five most frequent MICA alleles in the Greek population were *008, *009, *018, *002, 004. In other Caucasian populations, two of these alleles (008, and 004) were observed in similar frequencies. MICA002 was observed less frequently (8.02%) in the Greek population compared to other Caucasian groups (frequencies > 15%). Also, MICA009 and MICA018 had elevated frequencies (above 15%) whereas in other Caucasian populations they were found around 10% or less. These data may be important for the elucidation of the role that MICA polymorphisms play in organ and stem cell transplantation and to identify the relation of certain MICA with susceptibility to specific diseases.