HLA-DR1 (DR1) is a HLA-DR serotype that recognizes the DRB1*01 gene products. It has been observed to be common among centenarians.

The serology for the most common DR1 alleles is excellent. The serology for alleles *01:04, *01:06, *01:09, *01:10, *0112, *0115, and *0116 is unknown.

DR1 is associated with seronegative-rheumatoid arthritis, penicillamine-induced myasthenia, and schizophrenia. DR1 is increased in patients with systemic sclerosis and arthritis and in ulcerative colitis with patients that have articular manifestations.

DRB1*01:01 is associated with rheumatoid arthritis, in anti-Jk(a) mediated hemolytic transfusion reactions, foliaceous pemphigus, HTLV-1-associated myelopathy/tropical spastic paraparesis, and lichen planus. In lyme disease arthritis, *01:01 appears to play a role in presentation of triggering microbial antigens.

DRB1*01:02 is associated with rheumatoid arthritis, in anti-Jk(a) mediated hemolytic transfusion reactions, psoriasis vulgaris, and recurrent respiratory papillomatosis

DRB1*01:03 is associated with colonic Crohn's disease and ulcerative colitis.

DRB1*01:01/*0404 and *01:01/*0401 increases risk of mortality in rheumatoid arthritis, with ischemic heart disease and smoking. these same genotypes are associated with rheumatoid vasculitis.

DRB1*01:02:DQB1*05:01 is associated with psoriasis vulgaris and tubulointerstitial nephritis & uveitis syndrome, but is relatively protective against juvenile diabetes.