Heterogeneous immune populations in virus infection model. In both acute and chronic infection, early effector (EE) cells differentiate in a parallel manner into various CD8⁺ T cell subsets. Notable distinctions in trafficking patterns are signified by residence in lymphoid organs (gray), blood (red), or peripheral tissues (green). In acute infection, several effector and memory states are found. TE cells are typically found in the red pulp of spleen or blood, whereas MP cells are primarily found in white pulp or lymphoid structures, but they are also capable of recirculation. T_CM and T_EM cells both circulate in the blood, but T_CM cells predominate in lymphoid organs, whereas T_EM cells are also found in tissues. T_PM cells are proposed to circulate throughout lymph, blood, and tissues. T_RM cells do not circulate much and reside long-term in tissues. As in acute infection, heterogeneous states and distinct localization of CD8⁺ T cells are found in chronic infection. Tex_prog and MP cells are often observed in lymphoid structures, yet their circulation tendency might not be equivalent. Tex_int and Tex_term cells are predominantly found in blood and peripheral tissue, respectively.