Molecular mechanisms of CD8⁺ T cell trafficking and localization

Cytotoxic CD8⁺ T cells are potent mediators of host protection against disease due to their ability to directly kill cells infected with intracellular pathogens and produce inflammatory cytokines at the site of infection. To fully achieve this objective, naïve CD8⁺ T cells must be able to survey the entire body for the presence of foreign or "non-self" antigen that is delivered to draining lymph nodes following infection or tissue injury. Once activated, CD8⁺ T cells undergo many rounds of cell division, acquire effector functions, and are no longer restricted to the circulation and lymphoid compartments like their naïve counterparts, but rather are drawn to inflamed tissues to combat infection. As CD8⁺ T cells transition from naïve to effector to memory populations, this is accompanied by dynamic changes in the expression of adhesion molecules and chemokine receptors that ultimately dictate their localization in vivo. Thus, an understanding of the molecular mechanisms regulating CD8⁺ T cell trafficking and localization is critical for vaccine design, control of infectious diseases, treatment of autoimmune disorders, and cancer immunotherapy.