Human Interleukin-16 (IL-16) is also called lymphocyte chemoattractant factor (LCF) and it has three isoforms which are cleaved from pre-Interleukin-16. IL-16 is mostly secreted by lymphocytes, epithelial cells, eosinophils, and CD8+ T cells. It has many functions including induction of the IL-2Rα on T cells, suppression of human immunodeficiency virus (HIV) replication, inhibition of T-cell antigen receptor/CD3 mediated T-cell stimulation in mixed lymphocyte reactions and so on. It signals through CD4 receptor. Furthermore, recombinant human IL-16 (121 a.a.) contains 121 amino acid residues and it shares 85 % a.a. sequence identity with murine IL-16.