IL17A and colitis: Functionally, Tfh cells are divided into Tfh1, Tfh2, Tfh10, Tfh17, Tfh21, and Tfr cell lineages, which respectively produce or express interferon (IFN)-γ, IL-4, IL-10, IL-17, IL-21, and forkhead box (FOX)P3, and these are closely related to colitis (Fazilleau et al., 2009; Crotty, 2014; Jandl et al., 2017).