immunkomplementdiszreguláció

Immunkomplement, often referred to as the complement system, is a crucial part of the innate immune system. It comprises a group of proteins that circulate in the blood and body fluids in an inactive state. When activated, these proteins work in a cascade, much like blood clotting factors, leading to a variety of immune responses. The primary functions of the complement system include opsonization, where complement proteins coat pathogens, marking them for easier recognition and destruction by phagocytic cells; lysis of target cells, particularly bacteria and enveloped viruses, by forming a membrane attack complex (MAC) that creates pores in the cell membrane; and promotion of inflammation by releasing anaphylatoxins, which attract immune cells to the site of infection.

There are three main pathways for complement activation: the classical pathway, the lectin pathway, and the alternative pathway. The classical pathway is typically initiated by the binding of antibodies to antigens on the surface of a pathogen. The lectin pathway is triggered by the binding of mannose-binding lectin (MBL) or other lectins to carbohydrate structures on microbial surfaces. The alternative pathway is spontaneous and can be activated directly by certain microbial surfaces. Despite these different initiation routes, all three pathways converge on the generation of C3 convertase, an enzyme that cleaves C3, a central protein in the cascade. The subsequent cleavage of C3 leads to the formation of C5 convertase, which then drives the formation of the MAC and the release of inflammatory mediators. Regulation of the complement system is vital to prevent damage to host tissues, and a variety of regulatory proteins exist to control its activation. Deficiencies in complement components can lead to increased susceptibility to certain infections.