TNF and bacterial infectious disease: LPS is a surface antigen of the outer membrane of Gram-negative bacteria, through which macrophage cells are stimulated, thereby starting a cascade of reactions activating the release of nitric oxide (NO), prostaglandins, tumor necrosis factor α (TNF-α), pro-inflammatory cytokines interleukin 6 (IL-6) and cyclooxygenase 2 (COX-2), and other inflammatory mediators in the process of bacterial infection [13,14,15].