Fluorescently labeled anti-CD4 (RM4-5), -CD8 (53-6.7), -CD44 (IM7), -CD62L (MEL-14), -PD-1 (J43), -PD-L1 (B7-H1), -PD-L2 (B7-DC) monoclonal antibodies (mAb), and unlabeled anti-CD16/CD32 antibodies were all purchased from eBioscience. PE-conjugated H-2K b /Ova 257-264 pentamers were used to detect the CD8 + cells that specifically recognize the immunodominant Ova-derived SIINFEKL peptide using the manufacturers' protocol (Proimmune). Flow cytometry measurements of single cell suspensions derived from lymph nodes, spleen, or blood samples were performed using standard procedures and acquired on a FACS-Canto (BD Biosciences) instrument. Flow cytometry analyses were performed using the FlowJo software (Tree Star).