C3, Human, ELISA kit

C3, a central component in the complement system, plays a crucial role in both innate and adaptive immune responses. It acts as a frontline defense against pathogens, triggering inflammatory and protective reactions. Found in circulation, tissues, and body fluids, C3 is part of a complex protein and receptor family. Activation occurs via three pathways: the classical pathway, triggered by immune complexes; the lectin pathway, initiated by surface-bound lectins; and the alternative pathway (AP), activated by unprotected surfaces. These pathways converge to produce C3 convertase, which cleaves C3 into C3b, a major fragment. This process escalates into the formation of the membrane attack complex (MAC).

C3 synthesis varies across tissues, responding to diverse stimuli. Its cleavage results in anaphylotoxin C3a and C3b, the latter kickstarting the terminal complement pathway. Weighing around 185kDa, C3 stands as the most abundant complement protein, primarily produced by the liver and also by macrophages, neutrophils, and endothelial and epithelial cells.

C3’s high concentration and swift response to threats like pathogens make it a potent immune component. Deficiencies in C3 can lead to recurrent infections and autoimmune diseases. Although rare, C3 deficiency cases involve recurrent infections and impaired immune cell development. C3 polymorphism is linked to age-related macular degeneration (AMD) and atypical hemolytic uremic syndrome (aHUS). Furthermore, C3 assists in removing immune complexes, enhancing macrophage phagocytic capabilities. Dysfunctions in this system can lead to autoimmune diseases and tissue complement deposition, underscoring C3’s pivotal role in immune regulation.