Komplementisüsteemi

Komplementisüsteemi, also known as the complement system, is a crucial part of the innate immune response in humans and other vertebrates. It consists of a series of plasma proteins that work sequentially to identify and eliminate pathogens, such as bacteria, viruses, and fungi. The complement system enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promoting inflammation and attacking the pathogen’s cell membrane.

The complement system can be activated through three main pathways: the classical pathway, initiated by antibody-antigen complexes; the lectin pathway, triggered by mannose-binding lectin binding to pathogen surfaces; and the alternative pathway, which is continuously active at a low level and amplifies response upon recognizing foreign surfaces. Activation of these pathways results in a cascade of proteolytic cleavages, leading to the formation of key effector molecules.

These effector molecules include C3a and C5a, which act as inflammatory mediators recruiting immune cells, and C3b and C5b, which facilitate opsonization and formation of the membrane attack complex (MAC). The MAC creates pores on pathogen membranes, causing cell lysis. The complement system also plays a role in clearing immune complexes and apoptotic cells, preventing autoimmune responses.

Regulation of the complement system is tightly controlled to prevent damage to host tissues. Dysregulation or deficiencies can lead to increased susceptibility to infections or autoimmune disorders. Understanding the complement system is vital in developing treatments for immune-related conditions and designing novel antimicrobial therapies.