Interleukin-16 stimulates a migratory response in CD4+ lymphocytes, monocytes, and eosinophils. Primes CD4+ T-cells for IL-2 and IL-15 responsiveness. Also induces T-lymphocyte expression of interleukin 2 receptor. Ligand for CD4 (By similarity). Pro-interleukin-16 is involved in cell cycle progression in T-cells. 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. 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 (By similarity). Homotetramer (Probable). Pro-interleukin-16 interacts (via PDZ 2 domain) with PPP1R12A, PPP1R12B and PPP1R12C. Pro-interleukin-16 interacts with GRIN2A. Pro-interleukin-16 interacts with GABPB1. Pro-interleukin-16 interacts (via PDZ 3 domain) with HDAC3 (By similarity).