The CD4 marker on T helper cells and macrophages is used by HIV to gain access to these cells. Effector T cells release chemical regulators called cytokines. Cytokines are proteins produced by immune cells affect the behavior of other cells. Interferon that is released by virus-infected cells diffuses to uninfected cells. Uninfected cells are stimulated to make antiviral proteins that prevent viral replication.
Humans make three major forms of interferon.
Gamma interferon also stimulates macrophages to carry out phagocytosis. These are s mall cytokines that control the migration and activation of other cells, especially phagocytic cells and lymphocytes. They play a central role in inflammatory responses. The receptor for these chemokines is found on the surface of macrophages. Other chemokine receptors used by HIV have since been identified on other cells.