<h4>Background</h4>The aim of this prospective observational cohort study was to unveil the predictors of treatment response to tocilizumab (TCZ) therapy in rheumatoid arthritis (RA) patients, in terms of clinical characteristics and serum proinflammatory cytokines, especially to explore the predictive value of granulocyte macrophage-colony stimulating factor (GM-CSF).<h4>Methods</h4>Active adult RA patients with inadequate response to MTX intending to receive TCZ therapy were recruited prospectively in the study. Here, CSF2 is linked to rheumatoid arthritis.