IL-8, also known as neutrophil chemotactic factor, has two primary functions. It induces chemotaxis in target cells, primarily neutrophils but also other granulocytes, causing them to migrate toward the site of infection. IL-8 also stimulates phagocytosis once they have arrived. IL-8 is also known to be a potent promoter of angiogenesis. In target cells, IL-8 induces a series of physiological responses required for migration and phagocytosis, such as increases in intracellular Ca2+, exocytosis (e.g. histamine release), and the respiratory burst.IL-8 can be secreted by any cells with toll-like receptors that are involved in the innate immune response. Usually, it is the macrophages that see an antigen first, and thus are the first cells to release IL-8 to recruit other cells. Both monomer and homodimer forms of IL-8 have been reported to be potent inducers of the chemokine receptors CXCR1 and CXCR2. The homodimer is more potent, but methylation of Leu25 can block the activity of homodimers.