Complement component 5a

Complement component 5a (C5a) is a protein that in humans is encoded by the C5 gene. C5a is a potent inflammatory mediator and a powerful chemotactic factor for neutrophils and other white blood cells. It is one of the proteins formed by the cleavage of complement component 5 (C5) during complement activation.

Structure

C5a is a small glycoprotein composed of 74 amino acids and has a molecular weight of approximately 11 kDa. It is derived from the α-chain of C5 and retains the last 74 amino acids of this chain.

Function

C5a is a powerful inflammatory mediator and has many biological functions. It is a potent chemotactic factor for neutrophils, monocytes, eosinophils, and basophils, attracting these cells to the site of infection or inflammation. C5a also activates leukocytes, increasing their adhesion to endothelial cells and their production of reactive oxygen species and proinflammatory cytokines. In addition, C5a increases vascular permeability and stimulates the release of histamine from mast cells and basophils, contributing to the vasodilation and edema seen in inflammation.

Role in disease

Due to its potent inflammatory properties, excessive or uncontrolled production of C5a can lead to harmful inflammation and tissue damage. This has been implicated in a variety of diseases, including sepsis, autoimmune diseases such as rheumatoid arthritis and lupus, and allergic reactions.

See also

• Complement system
• Complement component 5
• Inflammation
• Chemotaxis