Contribution of LILRB1 polymorphism and HLA-DRB1-shared epitope to rheumatoid arthritis

Objectives: The LILRB1 gene has recently been associated with rheumatoid arthritis (RA) susceptibility in HLA-DRB1-shared epitope (SE) negative Japanese individuals. Since the contribution of the LILRB1 polymorphism to RA susceptibility may vary among ethnic populations, we examined this association in a group of Caucasian patients. The frequency of LILRB1 alleles was also determined in patients according to the presence of DRB1-SE. Methods: Samples from 103 RA patients and 107 healthy controls were randomly collected. Polymorphism of the LILRB1 gene was analyzed by sequencing with primers that amplified intron 3 and exon 4. Results: The frequencies of LILRB1 alleles in RA patients did not differ from those of controls. However, when patients and controls were grouped according to SE, the PE-01/01 genotype was less frequent in negative-SE patients than in controls. Whereas SE is associated with higher anti-CCP antibody levels, as expected, the production of anti-CCP antibodies was lower in negative-SE patients with PE-01/01 genotype. Moreover, radiographic damage in hand and feet of SE-negative PE-01/01 patients was less severe than in patients with other genotypes. Conclusions: The participation of this LILRB1 polymorphism in the RA pathogenesis of this Caucasian cohort differed fromthat reported in a Japanese sample. Our findings suggest that the LILRB1-PE-01/01 genotype could exert a protective role in RA susceptibility and disease severity in the absence of SE.