Fluorescent dye labeled antibodies

Fluorescent-dye-labeled antibodies against cell-surface markers CD4, CD8, CD44, CD62L, Gr1, CD19, CD45.1, CD45.2, CD127, CD27, and KLRG1 were purchased from eBioscience (San Diego, CA, USA). FITC- or PE-conjugated antibodies against cytokines were from BioLegend (San Diego, CA, USA). APC- or PE-conjugated K^b-ova+ tetramer was obtained from QuantoBio (Beijing, China). Splenic cells were depleted of erythrocytes by hypotonic lysis. The cells were washed with FACS washing buffer (2% FBS, 0.1% NaN₃ in PBS) twice and were then incubated with fluorescence-conjugated antibodies against cell-surface molecules for 30 min on ice in the presence of 2.4G2 mAb to block FcγR binding. Isotype antibodies were included as negative controls. For intracellular cytokine staining, single-cell suspensions were stimulated with 10 nM SIINFEKL peptide in the presence of Brefeldin A solution (eBioscience) for 6 h at 37 °C. After stimulation, cells were stained with fluorescence-conjugated antibodies against cell-surface markers, fixed, and permeabilized using a fixation/permeabilization kit (eBioscience) and stained with fluorescence-conjugated specific antibodies against Smad4 (Santa Cruz, Santa Cruz, CA, USA), IFN-γ, TNF-α, and GzmB in accordance with the manufacturer's instructions. Flow cytometry was performed using a Becton Dickinson FACSCalibur machine.