IL21 and colitis: Next, we evaluated the effect of BM-MSCs on the modulation of inflammatory cytokines and molecules closely related to the differentiation and immune regulatory effects of Tfh and Tfr in TNBS-induced colitis, assessed the relative expression level of Tfh's main transcription factor BCL-6 and Tfr's main transcription factor Foxp3 mRNA by RT-qPCR in inflamed colons, and detected serum IL-21, TNF-α, IL-10, and Tnfaip6 concentrations.