Anaphylatoxin

Anaphylatoxin

Structure of an anaphylatoxin

Anaphylatoxins are small peptides that are part of the complement system, which is a component of the immune system. They play a crucial role in the body's immune response by mediating inflammation and recruiting immune cells to sites of infection or injury.

Structure and Function

Anaphylatoxins are generated during the activation of the complement system. The most well-known anaphylatoxins are C3a, C4a, and C5a. These peptides are produced by the cleavage of complement proteins C3, C4, and C5, respectively.

C3a

C3a is a 77-amino acid peptide that is released from the cleavage of the complement protein C3. It functions primarily as a chemoattractant, drawing neutrophils and other immune cells to the site of infection. C3a also increases the permeability of blood vessels, facilitating the movement of immune cells and proteins into tissues.

C4a

C4a is less potent than C3a and C5a but still contributes to the inflammatory response. It is generated from the cleavage of C4 and plays a role in enhancing vascular permeability and attracting immune cells.

C5a

C5a is one of the most potent anaphylatoxins and is a powerful chemoattractant for neutrophils, monocytes, and macrophages. It also stimulates the release of histamine from mast cells and basophils, leading to increased vascular permeability and smooth muscle contraction.

Role in Disease

Anaphylatoxins are involved in various diseases due to their role in inflammation. Excessive or uncontrolled production of anaphylatoxins can lead to tissue damage and contribute to conditions such as anaphylaxis, asthma, and autoimmune diseases.

Anaphylaxis

In anaphylaxis, anaphylatoxins contribute to the rapid onset of symptoms by promoting widespread vasodilation and increased vascular permeability, leading to hypotension and shock.

Asthma

In asthma, anaphylatoxins can exacerbate airway inflammation and hyperresponsiveness, contributing to bronchoconstriction and respiratory distress.

Autoimmune Diseases

In autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis, anaphylatoxins can perpetuate chronic inflammation and tissue damage.

Related Pages

• Complement system
• Immune system
• Inflammation
• Anaphylaxis
• Asthma