Figure 2. CXCR3 is obligatory for murine CD8⁺ effector T cell trafficking to melanoma in vivo.

(a) Experimental scheme for short-term (1 h) competitive homing studies. The groups used for adoptive cell transfer (ACT) included WT OT-I cells comixed at a 1:1 ratio with WT OT-I cells, WT OT-I cells pretreated with PTX, Cxcr3^−/− OT-I cells, or WT OT-I cells pretreated with α-CXCR3 blocking Ab. Fluorescent-labeled CD8⁺ effector T cells were injected i.v. into mice with established B16-OVA tumors (tumor volume ~400–500 mm³) and homing was evaluated after 1 h. (b) Data represent ratio of adoptively transferred T cells relative to WT determined by flow cytometry in tumors and spleens following competitive homing assays. (c) The number of WT (red) or Cxcr3^−/− cells which successfully extravasated into underlying interstitium was quantified in histological tumor sections counterstained with CD31-specific Ab (green) to demark vessels. A representative photomicrograph of homed WT OT-I cells is shown with an example of an extravasated cell indicated by a white arrow and a vessel-associated cell noted by a white arrowhead. Scale bar, 100 μm. (d) Ratio of adoptively transferred T cells recovered in B16-OVA tumor-bearing mice pretreated with systemic thermal therapy (STT; 39.5 ± 0.5 °C for 6 h). PTX, pertussis toxin; α-CXCR3, CXCR3 blocking Ab. (b–d) All data (mean ± s.e.m.) are from ≥ 3 independent experiments (n ≥ 2 mice per group). * P < 0.001; ns, not significant; unpaired two-tailed Student’s t-test.