IL21 and rheumatoid arthritis: Regarding effector Tfh mediators, high levels of IL-21 mRNA transcripts were detected in peripheral blood mononuclear cells (PBMCs) from RA patients, and high levels of serum IL-21 correlated positively with DAS28 and the levels of serum anti- cyclic citrullinated peptide (anti-CCP) antibodies (22).