TNF and rheumatoid arthritis: MTs expression was further enhanced with the combination of IL-17 and TNF-α (Fig 2B; S2 Table), while the presence of the highest concentration of Zn affected less the expression of MTs in RA than in OA synoviocytes (i.e. in the presence of 3.6 ppm of Zn, MT-1F was 5.56 ± 1.49 in RA cells vs. 17.03 ± 8.50 in OA cells).