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Stroke has emerged as the second commonest cause of mortality worldwide and is a major public health problem. For the first time, we present here the association of human leucocyte antigen (HLA)-DRB1*/DQB1* alleles and haplotypes with ischaemic stroke in South Indian patients. Ischaemic stroke (IS) cases and controls were genotyped for HLA-DRB1*/DQB1* alleles by polymerase chain reaction sequence-specific primers (PCR-SSP) method. The frequencies of HLA class II alleles such as DRB1*04, DRB1*07, DRB1*11, DRB1*12, DRB1*13, DQB1*02 and DQB1*07 were high in IS patients than in the age- and gender-matched controls, suggesting that the individuals with these alleles are susceptible to ischaemic stroke in South India. The frequencies of alleles such as DRB1*03, DRB1*10, DRB1*14, DQB1*04 and DQB1*05 were less in IS cases than in the controls, suggesting a protective association. Haplotypes DRB1*04-DQB1*0301, DRB1*07-DQB1*02, DRB1*07-DQB1*0301, DRB1*11-DQB1*0301 and DRB1*13-DQB1*06 were found to be high in IS patients conferring susceptibility. The frequency of haplotype DRB1*10-DQB1*05 was high in controls conferring protection. IS-LVD and gender-stratified analysis too confirmed these susceptible and protective associations. Thus, HLA-DRB1*/DQB1* alleles and haplotypes strongly predispose South Indian population to ischaemic stroke. Further studies in different populations with large sample size or the meta-analysis are needed to explain the exact mechanism of associations of HLA gene(s) with IS.

The HLA-DQB1* region exhibits complex associations with autoimmune thyroid disease (AITD). AITD patients (Hashimoto's thyroiditis, HT = 180; Graves' disease, GD = 55) and age/sex matched controls (n = 235) were genotyped for DQB1* alleles by PCR-SSP. Alleles DQB1*02:02, *06:03, *06:09, *03:02, and *03:03 showed an increased risk and *02:01, *05:02, and *06:02 showed a protection toward AITD. Multiple sequence alignment was used to find out the amino acid variations within the peptide-binding pockets of susceptible and/or protective DQB1* alleles. We observed susceptible associations for amino acids 'Glu(P < 0.0007)' and 'Leu(P < 3.8 × 10)' in P1, 'Leu(P < 4.0 × 10)' in P4, 'His(P < 5.0 × 10)' and 'Ala(P < 3.6 × 10)' in P9 toward HT; and 'Gly(P < 0.0004)' in P1 and 'Asp(P < 1.9 × 10)' in P9 towards GD. Protective associations were observed for amino acids 'Ala(P < 8.2 × 10)' and 'Tyr(P < 0.0003)' in P1, 'Gly(P < 4.9 × 10)' and 'Ser(P < 4.9 × 10)' in P4, 'Phe(P < 0.0007)' and 'Ser(P < 0.0016)' in P9 towards HT. Thus, the present study revealed that DQB1* alleles and putative amino acid residues play an important role in susceptibility toward AITD in south India.

The aim of present study was to elucidate the association of CTLA4 +49 A/G and HLA-DRB1*/DQB1* gene polymorphism in south Indian T1DM patients. The patients and controls (n = 196 each) were enrolled for CTLA4 and HLA-DRB1*/DQB1* genotyping by RFLP/PCR-SSP methods. The increased frequencies of CTLA4 'AG' (OR = 1.99; p = 0.001), 'GG' (OR = 3.94; p = 0.001) genotypes, and 'G' allele (OR = 2.42; p = 9.26 × 10) were observed in patients. Reduced frequencies of 'AA' (OR = 0.35; p = 7.19 × 10) and 'A' (OR = 0.41; p = 9.26 × 10) in patients revealed protective association. Among HLA-DRB1*/DQB1* alleles, DRB1*04 (OR = 3.29; p = 1.0 × 10), DRB1*03 (OR = 2.81; p = 1.9 × 10), DQB1*02:01 (OR = 2.93; p = 1.65 × 10), DQB1*02:02 (OR = 3.38; p = 0.0003), and DQB1*03:02 (OR = 7.72; p = 0.0003) were in susceptible association. Decreased frequencies of alleles, DRB1*15 (OR = 0.32; p = 2.55 × 10), DRB1*10 (OR = 0.45; p = 0.002), DQB1*06:01 (OR = 0.43; p = 0.0001), and DQB1*05:02 (OR = 0.28; p = 2.1 × 10) in patients were suggested protective association. The combination of DRB1*03+AG (OR = 5.21; p = 1.4 × 10), DRB1*04+AG (OR = 2.14; p = 0.053), DRB1*04+GG (OR = 5.21; p = 0.036), DQB1*02:01+AG (OR = 4.44; p = 3.6 × 10), DQB1*02:02+AG (OR = 20.9; p = 9.5 × 10), and DQB1*02:02+GG (OR = 4.06; p = 0.036) revealed susceptible association. However, the combination of DRB1*10+AA (OR = 0.35; p = 0.003), DRB1*15+AA (OR = 0.22; p = 5.3 × 10), DQB1*05:01+AA (OR = 0.45; p = 0.007), DQB1*05:02+AA (OR = 0.17; p = 1.7 × 10), DQB1*06:01+AA (OR = 0.40; p = 0.002), and DQB1*06:02+AG (OR = 0.34; p = 0.001) showed decreased frequency in patients, suggesting protective association. In conclusion, CTLA4/HLA-DR/DQ genotypic combinations revealed strong susceptible/protective association toward T1DM in south India. A female preponderance in disease associations was also documented.