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

Serology

The serology for the most common DR1 alleles is excellent. The serology for alleles, , , , , , and is unknown.

Disease associations

By serotype

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.

By allele

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. **DRB101:02** 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.

By genotype

**DRB101:01/0404 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.

By haplotype

DRB101:02:DQB105:01 is associated with psoriasis vulgaris and tubulointerstitial nephritis & uveitis syndrome, but is relatively protective against juvenile diabetes. DR1-DQ5 is associated with tubulointerstitial nephritis & uveitis syndrome.

Rheumatoid arthritis

There frequency of DR4-DQ8 haplotypes reach extreme nodal levels. Arthritis has been identified in a pre-Columbian remains from Italy, the affected individual bearing the DRB101:01 allele. DRB101:01 and most DR4 have in common a 'shared epitope'. In this hypothesis a common region of the beta chain, positions 67 to 74, are common and may be integral to presenting auto-immunological peptides.

Genetic linkage

HLA-DR1 is not genetically linked to DR51, DR52 or DR53, but is linked to HLA-DQ1 and DQ5 serotypes.