Macrophages derived from blood monocytes play a crucial role in host defense against infection by processing and presentation of antigens to the lymphocytes, killing pathogenic microorganisms, removing cell debris, as well as secreting pro-inflammatory mediators such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and nitric oxide (NO) [10,11]. The gene discussed is TNF; the disease is infection.