Interleukin-16, also known as lymphocyte chemoattractant factor (LCF), is a chemotactic cytokine that stimulates a migratory response in CD4+ lymphocytes, monocytes, and eosinophils through binding to the CD4 receptor . IL-16 induces human T-lymphocyte expression of interleukin 2 receptor and upregurates major histocompatibility complex molecules on resting human T lymphocyte. It is able to render CD4+ T cells unresponsive to TCR/CD3 stimuli. Moreover, IL-16 inhibits the replication of T cell and monocyte tropic HIV strains in vitro.