Guo (89) investigated the effects of T cell–specific knockout of RhoA and Cdc42 on T cell development in the thymus, peripheral T cell homeostasis, activation, and differentiation to effector and regulatory T cells, in addition to T cell–mediated allergic airway inflammation and colitis, which play an important role in the pathogenesis of most, if not all, inflammatory diseases (89). Here, CDC42 is linked to colitis.