Immunogenetics of rheumatoid arthritis and primary Sjögren's syndrome: DNA polymorphism of HLA class II genes.

We investigated the DNA restriction fragment length polymorphism (RFLP) of the Major Histocompatability Complex (MHC) class II genes: HLA-DRB, -DQA, -DQB, DPA, and -DFB in 24 patients with rheumatoid arthritis (RA), in 19 patients with primary Sjögren's syndrome (primary SS), and healthy Danes. The frequencies of DNA fragments associated with the following HLA class II genes were increased in RA when compared to normal controls: DRB104 (DR4) (relative risk, RR = 7.4, P less than 10(-3), DRB40101 (DRw53) (RR = 9.6, P less than 10(-3), DQA10301 (RR = 9.6, P less than 10(-3), DQB10301 (DQw7) (RR = 2.8, P less than 0.05, 'corrected' P greater than 0.05), and DQB10302 (DQw8) (RR = 4.5, P less than 10(-2). Negative associations were found between RA and DRB11501 (DR2/DRw15) (RR = 0.2, P less than 10(-2) and DQB10602 (DQw6) (RR = 0.2, P less than 10(-2), 'corrected' P greater than 0.05). The frequencies in RA of other HLA class II associated DNA fragments including DPA and DPB and the antigens DPw1-w6 defined by primed lymphocyte stimulation, did not differ significantly from those in controls. In primary SS, the frequency of HLA-B8 was significantly increased (RR = 9.0, P less than 10(-3). Positive associations were found between primary SS and DNA fragments associated with DRB103/13 (RR = 6.8, P less than 10(-3), DRB30101 (DRw52) (RR = 5.7, P less than 10(-2), DQA10501 (RR = 6.8, P less than 10(-3), DQB10201 (DQw2) (RR = 11.6, P less than 10(-5), and DQB10602 (DQw6) (RR = 2.7, P less than 0.05, 'corrected' P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)