The complement system is a crucial part of the innate immune response, consisting of a series of proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens and damaged cells. It plays a role in inflammation and cell lysis, and can be activated through three pathways: classical, lectin, and alternative.

Complement System

complement system

The innate immune response is the body's first line of defense against pathogens, characterized by its rapid, non-specific action. It involves physical barriers, immune cells, and proteins that recognize and eliminate invaders without prior exposure or adaptation.

innate immune response

series of proteins

ability of antibodies

phagocytic cells

clear pathogens

damaged cells

role in inflammation

Cell lysis is the process of breaking down the cell membrane to release the cell's contents, often used in laboratory settings to extract proteins, nucleic acids, or other cellular components. This process can be achieved through mechanical, chemical, or enzymatic methods, each tailored to the specific type of cell and the desired outcome of the lysis.

cell lysis

Activated pathways

The classical pathway is one of the three pathways that activate the complement system, an essential part of the immune response, and is triggered by antibodies bound to antigens on the surface of pathogens. This pathway leads to a cascade of proteolytic events resulting in the formation of the membrane attack complex, opsonization, and recruitment of inflammatory cells to eliminate the pathogen.

Classical Pathway

The lectin pathway is a component of the innate immune system that activates the complement system through the binding of mannose-binding lectin (MBL) to pathogen surfaces. This pathway plays a crucial role in the body's first line of defense against infections by enhancing phagocytosis and promoting inflammation.

Lectin Pathway

The alternative pathway is a component of the innate immune system that activates the complement system without the need for antibodies, providing a rapid defense mechanism against pathogens. It is triggered by the spontaneous hydrolysis of complement component C3 and is regulated by various factors to prevent damage to host cells.

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