Editing Rheumatoid arthritis (section)

===HLA-DR1 and HLA-DRB1 gene===

The ''HLA''-''DRB1'' gene is part of a family of genes called the human leukocyte antigen (HLA) complex. The HLA complex is the human version of the major histocompatibility complex (MHC). Currently, have been identified at least 2479 different versions of the ''HLA''-''DRB1'' gene.<ref>{{cite journal | vauthors = Klimenta B, Nefic H, Prodanovic N, Jadric R, Hukic F | title = Association of biomarkers of inflammation and HLA-DRB1 gene locus with risk of developing rheumatoid arthritis in females | journal = Rheumatology International | volume = 39 | issue = 12 | pages = 2147–2157 | date = December 2019 | pmid = 31451934 | doi = 10.1007/s00296-019-04429-y | s2cid = 201644677 }}</ref> The presence of HLA-DRB1 alleles seems to predict radiographic damage, which may be partially mediated by ACPA development, and also elevated sera inflammatory levels and high swollen joint count. HLA-DR1 is encoded by the most risk allele [[HLA-DRB1]] which share a conserved 5-aminoacid sequence that is correlated with the development of anti-citrullinated protein antibodies.<ref>{{cite journal | vauthors = Gregersen PK, Silver J, Winchester RJ | title = The shared epitope hypothesis. An approach to understanding the molecular genetics of susceptibility to rheumatoid arthritis | journal = Arthritis and Rheumatism | volume = 30 | issue = 11 | pages = 1205–1213 | date = November 1987 | pmid = 2446635 | doi = 10.1002/art.1780301102 | doi-access = free }}</ref> HLA-DRB1 gene have more strong correlation with disease development. Susceptibility to and outcome for rheumatoid arthritis (RA) may associate with particular HLA-DR alleles, but these alleles vary among ethnic groups and geographic areas.<ref>{{cite journal | vauthors = Kapitány A, Zilahi E, Szántó S, Szücs G, Szabó Z, Végvári A, Rass P, Sipka S, Szegedi G, Szekanecz Z | title = Association of rheumatoid arthritis with HLA-DR1 and HLA-DR4 in Hungary | journal = Annals of the New York Academy of Sciences | volume = 1051 | issue = 1 | pages = 263–270 | date = June 2005 | pmid = 16126967 | doi = 10.1196/annals.1361.067 | s2cid = 6515443 | bibcode = 2005NYASA1051..263K }}</ref>