Figure 2.

CD8⁺ T cell memory formation. Naïve CD8⁺ T cells become activated by recognition of viral peptides presented in the context of MHC-I molecules on the surface of virally-infected APCs. Activated CD8⁺ T cells divide and differentiate into effector CD8⁺ T cells, which kill virus-infected cells and secrete cytokines to induce an anti-viral milieu. After viral clearance, mainly KLRG1^lo, ID3⁺, IL2Rα⁺, and CD62L^hi CD8⁺ T cells develop into CD8⁺ memory T cells, while the remaining ~90–95% of CD8⁺ T cells undergo apoptosis. Memory formation can be augmented by innate-like T cells (iNKT and MAIT cells). Memory CD8⁺ T cells are divided based on surface marker expression, known to impact their localization. While T_CM and T_EM can be found in blood and tissues, T_RM reside at the site of infection where they can rapidly respond towards a secondary infection. T_CM can be also found in lymph nodes and display higher proliferative capacity and IL-2 production compared to their T_EM counterparts.