MOST AFRICAN-AMERICAN PATIENTS WITH RHEUMATOID-ARTHRITIS DO NOT HAVE THE RHEUMATOID ANTIGENIC DETERMINANT (EPITOPE)

Objective: To evaluate the relation between the presence of the ''rheu matoid epitope,'' defined by a sequence motif in the HLA-DRB1 alleles, and disease severity in African-American patients with rheumatoid art hritis. Design: Cross-sectional study. Setting: Rheumatology outpatien t clinics at two university medical centers. Patients: 86 African-Amer ican patients with rheumatoid arthritis (66 seropositive and 20 serone gative for the rheumatoid factor) attending the clinics and 88 healthy African-American persons. Measurements: HLA-DRB1 alleles were determi ned by restriction fragment length polymorphism and by allele-specific oligonucleotide typing of polymerase chain reaction-amplified HLA-DRB 1 second exons. Results: With the exception of an increased frequency of HLA-DRB104 alleles in seropositive patients with rheumatoid arthri tis (27.3%) compared with controls (13.1%) (P = 0.02), the frequencies of HLA-DRB1 alleles were similar in patients and controls. Most serop ositive (48 of 66) and seronegative (15 of 20) patients were HLA-DR4 n egative, but some (7 of 48 seropositive patients and 3 of 15 seronegat ive persons) inherited the rheumatoid epitope on a non-DR4 allele. Dis ease features, including severity, were similar for patients without t he epitope and for those with either a single or a double dose of an e pitope-positive allele. Positivity for rheumatoid factor, but not for the rheumatoid epitope, was weakly associated with severity in these p atients. Conclusion: Most African-American patients with rheumatoid ar thritis did not express the rheumatoid epitope. The predisposition to and severity of rheumatoid arthritis in African-Americans appears to b e independent of the presence and dose of the shared rheumatoid epitop e.