Direct role of HLA-B5 in influencing susceptibility to Takayasu Aortoarteritis

To investigate genetic factors involved in the pathogenesis of Takayasu arteritis (TA), North Indian patients belonging to the states of Punjab, Haryana, Uttar Pradesh and Delhi were examined for HLA-class I and class II antigens and the data compared with healthy controls from the same ethnic group. Additionally, DNA typing was performed using polymerase chain reaction/sequence specific oligonucleotide probe (PCR-SSOP) technique to evaluate the distribution of molecular alleles in the healthy Indian population as compared to orientals and Western caucasoids. The frequency of HLA-B5 was significantly increased in patients as compared to controls (x2 = 32.5, corrected P value, Pc= 3 × 10−6, relative risk = 4.3). Serological splitting of B5 into B51 and B52 did not reveal an association with any of the two subtypes. Weak association was also noticed with DR8 in the patient group (x2 = 8.2, Pc= 0.05). Distribution of the molecular subtypes of various HLA-B and DR alleles indicated that although the Indian population is essentially caucasoid, it comprises of an admixture of both caucasoid as well as oriental alleles/haplotypes. The observations clearly suggest that (a) HLA-linked genes are involved in the development of Takayasu arteritis, and (b) rather than a subtype of B5, the whole molecule or its closely linked gene(s) influence susceptibility to TA.