Herein, we present a detailed description of the T-cell phenotype of RA patients on established biological therapies, obtained with two approaches: (1) a cross-sectional analysis of a high number of RA patients on a long-term treatment with anti-TNF or anti-IL-6R therapies; (2) we present the long-term follow-up results of our prospective study of anti-TNF-treated RA patients, in whom these parameters have serially been measured from the start of the anti-TNF treatment (short-term follow-up data have been published in [7]). Here, TNF is linked to rheumatoid arthritis.