The chemokine receptor CXCR6 is required for the maintenance of liver memory CD8⁺ T cells specific for infectious pathogens

It is well established that immunization with attenuated malaria sporozoites induces CD8⁺ T cells that eliminate parasite-infected hepatocytes. Liver memory CD8⁺ T cells induced by immunization with parasites undergo a unique differentiation program and have enhanced expression of CXCR6. Following immunization with malaria parasites, CXCR6-deficient memory CD8⁺ T cells recovered from the liver display altered cell-surface expression markers as compared to their wild-type counterparts, but they exhibit normal cytokine secretion and expression of cytotoxic mediators on a per-cell basis. Most importantly, CXCR6-deficient CD8⁺ T cells migrate to the liver normally after immunization with Plasmodium sporozoites or vaccinia virus, but a few weeks later their numbers severely decrease in this organ, losing their capacity to inhibit malaria parasite development in the liver. These studies are the first to show that CXCR6 is critical for the development and maintenance of protective memory CD8⁺ T cells in the liver.