Major histocompatibility complex class I chain‐related gene A in Thai psoriasis patients: MICA association as a part of human leukocyte antigen‐B‐Cw haplotypes

Abstract

Psoriasis is a chronic inflammatory skin disorder. Although the aetiology and pathogenesis of psoriasis are unproven, it is hypothesised that the major histocompatibility complex (MHC) gene/haplotype contributes to the susceptibility of psoriasis in many populations. MHC class I chain-related gene A (MICA), located 46-kb centromeric of HLA-B, is expressed on keratinocytes and fibroblasts. MICA is in linkage disequilibrium with HLA-B and is involved in natural killer-cell functions. To investigate the relative contribution of the MICA gene in the pathogenesis of psoriasis, extracellular polymorphisms of MICA were studied by polymerase chain reaction-sequence specific primers in 128 Thai psoriasis patients (87 and 41 were Types I and II, respectively) from Srinagarind Hospital, Faculty of Medicine, Khon Kaen University. The control group included 255 healthy, unrelated Northeast Thais. We observed 11 MICA alleles (or groups of alleles) in the patients. A comparison of the psoriasis patients and the control group revealed that MICA*010 and MICA*017 were associated with Type I psoriasis whereas only MICA*010 was associated with Type II. The haplotype analysis revealed that MICA*008-HLA-B*13-Cw*0602 and MICA*010-HLA-B*4601-Cw*01 were significantly increased in both Types I and II, whereas MICA*002-HLA-B*38-Cw*07 (01-03) and MICA*017-HLA-B*57-Cw*0602 were elevated only in Type I. MICA*010 was in strong linkage with Cw*01. Analysis of independent association of MICA*010 in individuals lacking Cw*01 failed to maintain an association. Our results suggest that a significant increase of the MICA alleles in the patient group is a part of HLA-B-Cw haplotypes. It is conceivable that an unknown susceptibility gene, on certain HLA-B-Cw haplotypes, is responsible for the development of psoriasis.

Allelic diversity of MICA gene and MICA/HLA-B haplotypic variation in a population of the Murcia region in southeastern Spain

“…Uncommon alleles, such as MICA*030, have also been observed in African Americans [28], and MICA*046 has been noted in Berbers [32]. Curiously, the MICA*052 allele was found to be frequent in a Thai population and to be associated with HLA-B*13 [33]. We also observed other particular characteristics in our population.…”

MICA-HLA-B haplotype diversity and linkage disequilibrium in a population of Jewish descent from Majorca (the Balearic Islands)

“…Of note were the elevated frequencies of some alleles, such as MICA*012, MICA*016, and MICA*017. These alleles had low frequencies in the majority of population studies but, curiously, the frequency of MICA*012 was remarkable in the Korean population [35], in the Japanese population [36], and in the northeastern Thai population [37]. MICA*017 with such high frequency was reported only in the Thai study [37] and frequencies higher than 2.3% have not been reported for the allele MICA*016 (8.9% in Chuetas [24 -32,35-39]).…”

“…These alleles had low frequencies in the majority of population studies but, curiously, the frequency of MICA*012 was remarkable in the Korean population [35], in the Japanese population [36], and in the northeastern Thai population [37]. MICA*017 with such high frequency was reported only in the Thai study [37] and frequencies higher than 2.3% have not been reported for the allele MICA*016 (8.9% in Chuetas [24 -32,35-39]). These particularities and the virtually undetectable frequency of MICA*001 and MICA*010 could be typical of Jewish populations, but it is difficult to draw conclusions because previous reports in Jewish populations have only focused on MICA transmembrane domain [40].…”

The Epidermis as an Adjuvant

“…In a small study, Molinero et al (2003) has documented that the expression of this molecule is increased in seborrheic dermatitis. Interestingly, the genetic association with MICA locus has been identified in psoriasis (Zwirner et al, 1998;Romphruk et al, 2004;Pollock et al, 2011). Although these studies suggest an involvement of the molecule in inflammatory process in the skin, the cellular contribution has not yet been identified.…”