Mononuclear cells were isolated as described previously with minor modifications9 (link). The colon was flushed, cut open longitudinally and incubated in 5 mM EDTA and 10% FBS-containing HBSS buffer to wash out intraepithelial mononuclear cells. The colon was then cut into small pieces, incubated in 5 ml digesting buffer contained 500 U collagenase from Clostridium histolyticum (C2139, Sigma-Aldrich), 2.5 μg DNase I (10104159001, Roche) and 10% FBS (Gibco) at 37 °C for 2 h. The digested colon was homogenized using a 70 μm strainer. CD45+ cells were isolated using a CD45 magnetic beads isolation kit (130-052-301, Miltenyi Biotec).