In the present work, the frequency of inherited polymorphisms of the beta2 adrenergic receptor (beta2AR) gene and their association with rheumatoid arthritis (RA) as well as human leukocyte antigen (HLA)-DRB1 alleles was examined.
An allele-specific polymerase chain reaction was used to determine the common variants of the beta2AR at positions 16, 27 and 164 in patients with RA (n=310) and ethnically matched healthy controls (n=305) from Germany. HLA-DRB1 genotyping was performed by oligonucleotide hybridisation of enzymatically amplified DNA allowing low-resolution HLA-DRB1 genotyping comprising specificities DRB1*01 to DRB1*17.
Arginine (Arg) at codon 16 was present in 278 patients with RA (89.7%) compared to 202 controls (66.2%; odds ratio (OR) 4.43, 95% CI 2.81 to 7.02, p<0.001). Homozygosity for Arg16 was found in 107 patients with RA (34.5%) compared to 14 controls (4.6%; OR 10.9, CI 5.9 to 20.5, p<0.001). Stratifying patients for their HLA-DR status revealed that homozygosity for Arg16 exhibited the greatest risk for RA in combination with HLA-DRB1*04 (OR 17.1, 95% CI 1.71 to 414.4, p=0.004). Interestingly, patients with the Arg16 allele have a younger mean (SD) age at disease onset compared to patients without Arg16 (46.1 (2.0) vs 53.1 (2.7) respectively, p<0.05). Furthermore, 93.3% patients with homozygosity for Arg16 were positive for anti-cyclic citrullinated peptide (CCP) antibodies vs 75% patients with homozygosity for Gly16 (p<0.05).
There was a highly significant distortion between patients with RA and controls in the distribution of beta2AR polymorphisms at codon 16, contributing (together with the HLA-DR alleles) to the genetic background of RA.