Introduction:

• The complement system is a complex network of proteins that enhances the ability of the immune system to clear pathogens from an organism.
• It is activated by the presence of pathogens and their associated molecules, leading to a cascade of reactions that ultimately results in the formation of the membrane attack complex (MAC).

Principles of Complement System:

• This system is activated through a cascade of reactions that leads to the formation of the MAC.
• The cascade of reactions is triggered by the presence of pathogens and their associated molecules.
• The MAC forms a pore in the membrane of the pathogen, leading to its lysis and removal from the organism.

Types:

• The complement system is activated through a cascade of reactions, which can be divided into three pathways: classical, lectin, and alternative pathways.
• The classical pathway is triggered by antibodies binding to pathogens.
• The lectin pathway is triggered by the binding of lectins to carbohydrates on the surface of pathogens.
• The alternative pathway is triggered by the spontaneous hydrolysis of C3 and the formation of C3 convertases.

Activation of Complement:

• The classical pathway is activated by the binding of antibodies to pathogens, recruiting C1q.
• The lectin pathway is activated by the binding of lectins to carbohydrates on the surface of pathogens, recruiting MASP-2.
• The alternative pathway is activated by the spontaneous hydrolysis of C3 and the formation of C3 convertases.

Functions:

• The complement system plays a key role in the innate immune response by enhancing the ability of antibodies and phagocytic cells to clear pathogens from an organism.
• It can also play a role in the adaptive immune response by helping to activate B cells and T cells.
• It can also play a role in the regulation of inflammation by releasing inflammatory mediators, such as C3a and C5a, which attract and activate leukocytes.

Regulation of Complement:

• The complement system is regulated by a number of proteins that control the activation and inactivation of the complement cascade.
• Proteins such as factor H, factor I, and C1 inhibitor act to control the activation of the complement cascade and prevent excessive activation and damage to host cells.

Conclusion:

• The complement system is a complex network of proteins that plays a key role in the immune response.
• Understanding the this is important in the field of immunology and for the development of complement-based therapeutics for the treatment of various diseases.