HLA-DRB1 and asthma: Since asthma is well-known as a heterogeneous polygenic disease, plenty of genetic studies of asthma in different populations have documented an association with polymorphisms of IL4, IL13, ADRB2, TNF, HLA-DRB1, FCER1B, L4RA, CD14, HLA-DQB1 and ADAM33 genes (2).