TNF and rheumatoid arthritis: Stimulation with an acidic condition (pH 6.8) or TNF-α enhanced the migration of RA-FLSs; on the other hand, co-stimulation with both the pH 6.8 condition and TNF-α revealed a mild or non-additive effect on the migration of RA-FLSs (Fig. 3i, Supplementary Fig. 9).