 This study will be performed as a prospective observational open-labeled study non-interventional to evaluate the impact of TCZ treatment on the evolution of circulating Tfh cells levels. The administration of treatments TCZ and MTX will be done according to current practice, and will not be motivated by the inclusion in this study. TCZ will be administered in association with a conventional DMARD, or in monotherapy, according to clinical recommendations. The objective of this study is to analyze the impact of new therapy set-up, and patients included in the TCZ group would be under MTX treatment for at least 3 months. The immunological analysis will be performed with drop-off of blood samples used in the recommended follow-up of patients treated by MTX or TCZ. For the healthy controls, the immunological analysis will be performed with drop-off of blood samples used in the recommended follow-up of patients treated for osteoporosis or osteoarthritis. 