PP4 deficient T cells are hypo-responsive to antigen stimulation, differentiate into Th17 cells ineffectively, and fail to induce experimental colitis. A-B, Mice were immunized with KLH/CFA as described in the Materials and Methods. One wk later draining popliteal LN cells were restimulated in vitro with KLH; the proliferation of responding T cells (A) and their cytokine secretion in culture supernatants (B) were assessed on d 3 (n = 6). C, Naïve T cells were cultured in Th1-, Th2- or Th17-polarizaing conditions for 3 d, followed by intracellular cytokine staining for measuring their polarization efficiency. Representative flow cytometry plots are shown. Statistical analyses results are shown (n = 4-7). D-E, CD4+CD45RBhigh cells were sorted and transferred (4x105/mouse) into RAG1-/- mice (D). The recipients’ weight changes were monitored for 21 d (E = 3, n = 5 ~ 6) (E). See Additional file1: Figure S1 for flow cytometry gating strategies.