RC3H1 and Splenomegaly: The combined deficiency of Rc3h1 and Rc3h2 in peripheral T cells or the sanroque mutation in Rc3h1 induces spontaneous activation of T cells and differentiation of T helper cells into Tfh, Th1, or Th17 subsets or conversion of Treg into Tfr cells, causing pathologies that include lymphadenopathy, splenomegaly and inflammation in lung, kidney, and stomach2,6–8.