Interleukin 16 (IL-16), also named lymphocyte chemoattractant factor (LCF), is a 14-17 kDa single chain non-glycosylated polypeptide that was originally identified as a CD8+ T cell-derived chemoattractant for CD4+ cells. The expression of IL-16 precursor mRNA has been detected in various tissues including spleen, thymus, lymph nodes, peripheral leukocytes, bone marrow and cerebellum. In addition to its chemotactic properties, IL-16 has also been shown to suppress HIV-1 replication?in vitro.