Infections associated with HIV lead to the activation of the monocyte–macrophage system and initiate an early response characterized by the production of proinflammatory cytokines and chemokines such as interleukin (IL)-1, IL-6, IL-8, IL-15, tumour necrosis factor (TNF)-α, granulocyte–macrophage colony-stimulating factor (GM-CSF), and macrophage inflammatory protein (MIP)-lα, among others, and an increase in CD4+ T lymphocytes and interferon (IFN)-γ. Here, CD4 is linked to infection.