CCR9^–/– OT-II cells are as efficient as WT OT-II cells in their homing to and proliferation within MLNs. (A-B) Short-term homing of CCR9^–/– and WT OT-II cells into MLNs. CCR9^–/– and WT OT-II cells were coinjected into C57BL/6J.Ly5.1 recipients and the CCR9^–/–/WT OT-II cell ratio in the MLNs and blood assessed 24 hours later. (A) Representative flow cytometry analysis of WT and CCR9^–/– OT-II cells in MLNs. (B) Ratio of small CD62Lhi CCR9^–/– to WT OT-II cells in the input population, MLNs, and blood. Mean (SEM) of 3 mice from one representative experiment of 4 performed. (C) In vivo proliferation of CCR9^–/– and WT OT-II cells. The CCR9^–/–/WT OT-II cell ratio in the MLNs and blood in the absence of antigen (□) or 3 days after intraperitoneal administration of OVA plus LPS (▦). Mean (SEM) of 3 to 4 mice from one representative experiment of 2 performed. (D) In vitro proliferation of WT and CCR9^–/– OT-II cells. WT (▪) and CCR9^–/– (▦) OT-II cells were cultured together with the indicated number of OVA-pulsed MLN DCs. Mean (SD) of triplicate wells from one representative experiment of 3 performed. (E) Chemokine receptor expression on CCR9^–/– and WT OT-II cells in MLNs, 2 days after intraperitoneal administration of OVA plus LPS. Mean (SEM) of 3 experiments using cells pooled from 2 to 3 mice/experiment except for CCR8, which is the mean of 2 experiments.