Tumor necrosis factor alpha (TNF-A) is an inflammatory cytokine secreted by macrophages, monocytes, neutrophils, T cells, and NK-cells following stimulation by bacterial lipopolysaccharide (LPS). TNF-A signal activation occurs through two receptors, TNFR1 and TNFR2. TNFR1 is expressed on most cell types, unlike TNFR2, which is expressed mainly on immune cells. TNF-A functions to stimulate phagocytosis in macrophages, chemoattract neutrophils, increase insulin resistance, and induce fever.