CD8A and viral infectious disease: In acute viral infections, CD8 T cells primed in the absence of CD4 T cells (“unhelped” CD8 T cells) lose the ability to produce effector cytokines such as IFN-γ, TNF-α, IL-2, as well as the cytolytic protein granzyme B, and are unable to control primary infection or infections by reencountered pathogens [12–14].