CX3CR1 and viral infectious disease: Memory T cells are subdivided by various cell-surface markers, including CD27, CD127, CD43, CXCR3 and CX3CR1 (5–8). A study using CX3CR1-reporter mice reveals that CX3CR1hi CD8+ TEM cells were largely excluded from peripheral tissues after viral infection, providing novel insight concerning CD8+ TEM cells (9).