TNF and AIDS: Elevated levels of NO synthase has been reported in the brain of HAD patients, while a 40-fold increase in expression of NO synthase in neurons of drug addict HIV patients.[66, 67] TNF-α is produced by macrophages and microglia and it mainly affects oligodendrocytes.[68] An elevated level of TNF-α mRNA has been reported in HIV patients with neurological complications.[69] TNF-α causes damage to BBB and facilitates entry of peripheral blood cells.[70] Pro-inflammatory cytokines like TNF-α, IL-1, and IFN-α are found to be present in elevated level in AIDS patients.[71, 72]