With the help of cytokines such as IFN-γ, IL-2, and IL-10 secreted by CD4+ T helper cells, CD8+ effector cells migrate from lymphoid tissues to the site of infection, inducing lysis in infected cells via Fas–FasL interactions or exocytosis of granule-associated proteases containing perforin and granzymes [67,68]. Here, CD4 is linked to infection.