macrophages, dendritic cells, histiocytes, Kupffer cells, and mast cells. These cells present receptors contained on the surface or within the cell, named pattern recognition receptors (PRRs), which recognize molecules that are broadly shared by pathogens but distinguishable from host molecules, collectively referred to as pathogen-associated molecular patterns (PAMPs). At the onset of an infection, burn, or other injuries, these cells undergo activation (one of their PRRs recognizes a PAMP) and release inflammatory mediators, like cytokines and chemokines, which are responsible for the clinical signs of inflammation. PRR activation and its cellular consequences have been well-characterized as methods of inflammatory cell death, which include pyroptosis, necroptosis, and PANoptosis. These cell death pathways help clear infected or aberrant cells and release cellular contents and inflammatory mediators. Chemical factors produced during inflammation (histamine, bradykinin, serotonin, leukotrienes, and prostaglandins) sensitize pain receptors, cause local vasodilation of the blood vessels, and attract phagocytes, especially neutrophils. Neutrophils then trigger other parts of the immune system by releasing factors that summon additional leukocytes and lymphocytes. Cytokines produced by macrophages and other cells of the innate immune system mediate the inflammatory response. These cytokines include TNF, HMGB1, and IL-1. The inflammatory response is characterized by the following symptoms: redness of the skin, due to locally increased blood circulation; heat, either increased local temperature, such as a warm feeling around a localized infection, or a systemic fever; swelling of affected tissues, such as the upper throat during the common cold or joints affected by rheumatoid arthritis; increased production of mucus, which can cause symptoms like a runny nose or a productive cough; pain, either local pain, such as painful joints or a sore throat, or affecting the whole body, such as body aches; and possible dysfunction of involved organs/tissues. Complement system The complement system is a biochemical cascade of the immune system that helps, or “complements”, the ability of antibodies to clear pathogens or mark them for destruction by other cells. The cascade is composed of many plasma proteins, synthesized in the liver, primarily by hepatocytes. The proteins work together to: trigger the recruitment of inflammatory cells "tag" pathogens for destruction by other cells by opsonizing, or coating, the surface of the pathogen form holes in the plasma membrane of the pathogen, resulting in cytolysis of the pathogen cell, causing its death rid the body of neutralised antigen-antibody complexes. The three different complement systems are classical, alternative and lectin.