Interleukin 16

Interleukin 16 is a cytokine released by a variety of cells including lymphocytes and epithelial cells expressing the cell surface molecule CD4.

Function
It recruits and activates other cells expressing CD4, including lymphocytes, monocytes, and eosinophils.

ME/CFS
Landi et al (2015) found IL-16 to be significantly downregulated in long term CFS patients. It is a pro-inflammatory cytokine and the reduction shown may indicate immunodeficiency. In mice studies low IL-16 is correlated with impaired development of B cells. Most studies into human disease seem to show increases in IL-16 not a decrease (asthma, rheumatoid arthritis, Lupus, MS). The other condition which shows a decrease is HIV and IL-16 may repress HIV-1 replication (Indinavir used in HIV patients increases circulating IL-16). IL-16 has a developmental role in the human immune system. It is also related to neuronal development and may account for brainfog symptoms.