For flow cytometry analysis, spleens were harvested from mice and processed as previously described[39 (link)]. Extracted lungs were chopped in small pieces and incubated with a digestive mix containing RPMI with collagenase IV (50 μg/ml) and DNAseI (20 U/ml) for 30 min at 37 °C. Spleens and lungs were mashed through a 70-μm strainer before red blood cells were lysed using ammonium-chloride-potassium (ACK) lysis (Gibco). Cells were washed with PBS containing 1% FCS and surface receptors were stained using various antibodies. Fluorochrome-conjugated antibodies against mouse CD3, CD4, CD44, CD38, ICOS, OX40, CD62L, Perforin, Granzyme B and Tbet, CXCR5 were purchased from Biolegend. Fluorochrome-conjugated antibodies against mouse CD8a were purchased from BD Biosciences. Fluorochrome-conjugated antibodies against CXCR3 and Ki67 were purchased from Thermofisher. Stained cells were fixed with PBS containing 4% Formaldehyde. For intracellular staining, the forkhead box P3 (FOXP3) staining buffer set was used (eBioscience). Flow cytometry analysis was performed on a LSR II machine (BD Bioscience) and data were analyzed using FlowJo (Tree Star).