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 "rheumatoid epitope," defined by a sequence motif in the HLA-DRB1 alleles, and disease severity in African-American patients with rheumatoid arthritis.


METHODS
Cross-sectional study.


METHODS
Rheumatology outpatient clinics at two university medical centers.


METHODS
86 African-American patients with rheumatoid arthritis (66 seropositive and 20 seronegative for the rheumatoid factor) attending the clinics and 88 healthy African-American persons.


METHODS
HLA-DRB1 alleles were determined by restriction fragment length polymorphism and by allele-specific oligonucleotide typing of polymerase chain reaction-amplified HLA-DRB1 second exons.


RESULTS
With the exception of an increased frequency of HLA-DRB1*04 alleles in seropositive patients with rheumatoid arthritis (27.3%) compared with controls (13.1%) (P = 0.02), the frequencies of HLA-DRB1 alleles were similar in patients and controls. Most seropositive (48 of 66) and seronegative (15 of 20) patients were HLA-DR4 negative, but some (7 of 48 seropositive patients and 3 of 15 seronegative persons) inherited the rheumatoid epitope on a non-DR4 allele. Disease features, including severity, were similar for patients without the epitope and for those with either a single or a double dose of an epitope-positive allele. Positivity for rheumatoid factor, but not for the rheumatoid epitope, was weakly associated with severity in these patients.


CONCLUSIONS
Most African-American patients with rheumatoid arthritis did not express the rheumatoid epitope. The predisposition to and severity of rheumatoid arthritis in African-Americans appears to be independent of the presence and dose of the shared rheumatoid epitope.
McDaniel
D O
DO
University of Alabama at Birmingham, USA.
Alarcón
G S
GS
Pratt
P W
PW
Reveille
J D
JD
D000328:Adult; D000368:Aged; D000483:Alleles; D000595:Amino Acid Sequence; D001172:Arthritis, Rheumatoid / Q000208:ethnology / Q000276:immunology*; D044383:Black People / Q000235:genetics; D003430:Cross-Sectional Studies; D015342:DNA Probes; D005260:Female; D005838:Genotype; D006684:HLA-DR Antigens / Q000235:genetics / Q000276:immunology*; D059811:HLA-DRB1 Chains; D006801:Humans; D016056:Immunodominant Epitopes / Q000097:blood*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D012150:Polymorphism, Restriction Fragment Length; D015995:Prevalence; D012720:Severity of Illness Index; D001741:Black or African American
D015342:DNA Probes; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; D016056:Immunodominant Epitopes