CD8A and cancer: Transitory cells are migratory; circulating antigen-specific CD8+ T cells in cancer and chronic infection are found in this state, which is marked by CX3CR1 expression.19, 20, 21, 22, 23, 24 Upon migration to non-lymphoid tissues, transitory cells further differentiate into a terminally differentiated population with increased expression of inhibitory molecules.19, 20, 21 These terminally differentiated CD8+ T cells are resident in non-lymphoid tissues, have poor effector function, and lack proliferative capacity.19