Mouse interleukin-16(IL-16) is a single chain non-glycosylated polypeptide. IL-16 is widely expressed in human tissues including spleen, thymus, lymph nodes, peripheral leukocytes, bone marrow and cerebellum. IL-16 plays an important role instimulating a migratory response in CD4+ lymphocytes, monocytes, and eosinophils,inducing T-lymphocyte expression of interleukin 2 receptor.It was originally identified as a CD8+ T cell-derived chemoattractant for CD4+ cells. In addition to its chemotactic properties, IL-16 has also been shown to suppress HIV-1 replication in vitro and appears to be involved in transcriptional regulation of SKP2 and is probably part of a transcriptional repression complex on the core promoter of the SKP2 gene. It may act as a scaffold for GABPB1 (the DNA-binding subunit the GABP transcription factor complex) and HDAC3 thus maintaining transcriptional repression and blocking cell cycle progression in resting T-cells.