PON1 and rheumatoid arthritis: Interestingly, anti-TNF-alpha therapy response was found to be associated with SNPs in the PON1 locus [48] and a recent case-control study on atherosclerosis in rheumatoid arthritis found a correlation between PON-1 activity and serum TNF-alpha and IL-6 levels [49], emphasizing the close regulatory interrelation between PON1 activity and TNF-alpha levels.