IL21 and Splenomegaly: Compared to WT mice, expression of genes involved in Tfh differentiation, including Gzmb, Pdcd1, Bcl6, Maf, Cxcr5, and Il21, was unaltered or only mildly increased in Treg cells isolated from the Tet2/3fl/flFoxp3Cre mouse with moderate splenomegaly (DKO), but markedly increased in Treg cells isolated from the littermate mouse with more severe splenomegaly (DKO*) (Fig. 4e, left panel).