Interleukin 16 (IL-16) is a proinflammatory cytokine of 691 amino acids (molecular weight 67kDa) which was originally discovered as lymphocyte chemoattractant factor in 1982. This interleukin has been shown to recruit and activate cells expressing the CD4 molecule, including monocytes, eosinophils, and dendritic cells. In addition to the activation of CD4 + T cells, IL-16 can promote the secretion of inflammatory cytokines such as tumor necrosis factor (TNFα), interleukin-1β (IL-1β), and interleukin-6 (IL-6). The measurement of IL-16 plasma levels may be useful in a personalized medicine approach for lung disease. In addition, serum IL-16 levels have been shown to be increased in nasopharyngeal carcinoma patients.