HLA-DRB1 and obesity due to melanocortin 4 receptor deficiency: Additionally, interactive effects have been shown between HLA-DRB1*15:01 and obesity: individuals classed as obese who carry HLA-DRB1*15 but not HLA-A*02 have an OR of 16.2 (95% CI 7.5, 35.2) for developing MS [35].