The supernatant was passed through a nylon wool (Cellular Products) column. The collected cells were centrifuged through a 45%/65% Percoll (GE Healthcare) gradient (800

× g, 20 min) to collect iIELs at the interface. Cells (105 cells/sample) were stained with mAb in staining buffer (PBS-2%FBS-0.02% NaN3) for 15 min on ice and analyzed by FACSCalibur or LSRII (BD Bioscience). The following antibodies conjugated with Alexa 405, allophycocyanin, Alexa 647, PE, PECy7 or biotin (prepared in our lab or purchased from eBioscience, or Biolegend) were used: CD4 (GK1.5), CD8α (53.6.7), CD8β (53.5.8), TCRβ (H57.597), TCRδ (GL3). Samples stained with biotin-conjugated Ab were subsequently stained with streptavidin (SA)-allophycocyanin or SA- allophycocyanin-Cy7 (eBioscience or Biolegend). Total iIELs were prepared as described above up to nylon wool filtration. IECs and CD4+ cells were removed

p38 MAPK assay by complement-mediated lysis with mAbs specific for MHC class II (BP107.2, 28-16-8s, Alisertib 25-5-16s) and CD4 (RL172.4). Live iIELs were recovered by 45%/65% Percoll gradient centrifugation, and stained with anti-CD4-PE, anti-CD8β-PE, and anti-CD8α-biotin mAb. CD8αα+ cells were isolated by depletion of CD4+ and CD8β+ cells with anti-PE mAb-conjugated MicroBeads (Miltenyi Biotec) and then by positive collection with SA-MicroBeads (Miltenyi Biotec) using auto-MACS (Miltenyi Biotec). The resultant preparation contained 96–98% CD8αα+ cells. After surface staining, cells were fixed with 4% paraformaldehyde for 30 min on ice. Cells were then stained with the FITC-conjugated anti-mouse Bcl-2 kit or PE-conjugated anti-human BCL-2 kit (BD Science) following the manufacturer’s instructions, or with FITC-mouse anti-human/mouse Bcl-xL (Southern Biotech) or FITC-mouse IgG3 (e-Biosciences) in staining buffer containing 0.1% saponin. Samples were analyzed using FACSCalibur or LSR II (BD Science). CD8αα+ iIELs were cultured in

Janus kinase (JAK) a 96-well plate (1 × 105 cells/200 μL) in RPMI 1640 (Invitrogen) supplemented with 2 mM l-glutamine, 20 mM HEPES, 2000 U/L penicillin/streptomycin, 5 × 10−5 M 2-ME and 10% FBS with or without murine IL-15 (eBioscience) for indicated hours. Some experiments included inhibitors in the culture: U0126, LY294002, wortmannin, SB203580, rapamycin, Akt IV, Jak3 inhibitor I (Sigma-Aldrich, or Calbiochem), ABT-737 or its enantiomer A-793844.0 (Abbott Laboratories). All cultures were in triplicate. Cells were collected and stained with propidium iodide (PI) (0.25 μg/mL in PBS containing 2% FBS and 0.02% NaN3), and analyzed by FACSCalibur or LSR II. For cell-cycle analysis, cells were fixed in cold 70% ethanol overnight, stained with PI (50 μg/mL in PBS containing 100 U/mL RNase A and 0.1% glucose), and analyzed by FACSCalibur. CD8αα+ iIELs were labeled with CFSE (5 μM) using Vybrant CFDA SE CellTracer kit (Life technologies) following the manufacturer’s instructions, and injected into recipient mice via the tail vein.