CX3CL1 and neoplasm: Given the decreased expression of CXCR3 in peripheral CX3CR1+ subsets (Fig. 2H) and the presence of the CX3CR1+ subset in the tumor despite FTY720 administration (Fig. 3C), we hypothesized that CX3CR1+ subsets could directly differentiate from the CX3CR1− subset in situ rather than trafficking to the tumor mediated via the CX3CR1/CX3CL1 pathway.