The apparent disparities between the respective functional effects of the two alleles on disease risk might also provide a mechanistic basis for an imputation-based conclusion that DRB1*03:01/DRB1*15 heterozygosity confers a greater risk for SLE than either DRB1*03:01/DRB1*03:01 or DRB1*15/DRB1*15 homozygosity52. The gene discussed is HLA-DRB1; the disease is systemic lupus erythematosus.