Specific interaction between genotype, smoking and autoimmunity to citrullinated α-enolase in the etiology of rheumatoid arthritis

Gene-environment associations are important in rheumatoid arthritis (RA) susceptibility, with an association existing between smoking, HLA-DRB1 'shared epitope' alleles, PTPN22 and antibodies to cyclic citrullinated peptides(CCP). Here, we test the hypothesis that a subset of the anti-CCP response, with specific autoimmunity to citrullinated α-enolase, accounts for an important portion of these associations. In 1,497 individuals from three RA cohorts, antibodies to the immunodominant citrullinated α-enolase CEP-1 epitope were detected in 43-63% of the anti-CCP-positive individuals, and this subset was preferentially linked to HLA-DRB104. In a case-control analysis of 1,000 affected individuals and 872 controls, the combined effect of shared epitope, PTPN22 and smoking showed the strongest association with the anti-CEP-1-positive subset (odds ratio (OR) of 37, compared to an OR of 2 for the corresponding anti-CEP-1-negative, anti-CCP-positive subset). We conclude that citrullinated α-enolase is a specific citrullinated autoantigen that links smoking to genetic risk factors in the development of RA. © 2009 Nature America, Inc. All rights reserved.