TRPA1 and rheumatoid arthritis: Pain and disability levels correlated with TRPA1 expression levels on leukocytes (r = 0.329 and r = 0.390; respectively; p < 0.05; Figure 1D) as this receptor was markedly increased (2.6-fold) in patients who had been recently diagnosed with RA in comparison with those of healthy subjects and patients under LFN or ADA therapy (Figure 1C).