FOXP3 and Splenomegaly: At 14 weeks of age, Foxp3-Cre Tet2/3fl/fl mice could be divided into two groups distinguished by moderate or severe splenomegaly and lymphadenopathy (Fig. 1A), defined as DKO-moderate and DKO-severe respectively depending on whether they had fewer than or more than 4 × 108 splenocytes and peripheral lymphocytes (from cervical and inguinal) (Fig. 1B).