Joint study of the associations of HLA-B and the transmembrane STR polymorphism of MICA with alopecia areata shows independent associations of both of them with the disease

Alopecia areata is a skin disease that produces hair loss in patches of skin. The underlying mechanism of alopecia areata is a loss of immune privilege by hair follicles, which are then attacked by NK cells. A genome-wide association study (GWAS) linked single nucleotide polymorphisms (SNPs) of MHC Class I Chain-Related A (MICA) to this disease. MICA is the ligand for the activating receptor NKG2D, expressed mainly in NK cells and CD8+ T cytotoxic cells. Since the aforementioned study did not include short tandem repeats (STR) of MICA, we will study their association with alopecia areata, alongside with that of the locus B of HLA, which is closely linked to MICA. In this paper, we investigate the association of a STR variation of MICA with alopecia areata by performing DNA amplicons size analysis . HLA-B locus genomic typing was perfomed by PCR-SSO. We observed an association between both MICA*009 and HLA-B14 with alopecia areata; associations were also observed between HLA-B alleles and MICA alleles which have both been previously found to be connected with AA, but never studied together. We conclude that it is important to study HLA-B and MICA together to avoid the influence of their association in experiments in which they are investigated separately.