TNF and rheumatoid arthritis: In our study, serum levels of IL-6, IL-17 and TNF-α were found to be significantly higher (p = 0.0059, p = 0.00192, p = 0.0237, respectively) in the overweight group with RA (BMI>25) than in lean controls (BMI<18.5) (Fig. 2C, E, G).