anafilatoxinek

Anafilatoxinek, also known as anaphylatoxins in English, are small peptide fragments generated during the activation of the complement system. The best-characterized members are C3a, C4a, and C5a. They arise when C3, C4, and C5 are cleaved by convertases formed through the classical, lectin, or alternative pathways. These fragments function as inflammatory mediators that help coordinate the immune response but can contribute to pathology if produced excessively.

The primary mechanism of action involves binding to specific receptors on immune and endothelial cells. C3a interacts with C3a receptors (C3aR), while C5a binds to C5a receptors (CD88) and related receptors such as C5L2. C4a has a less clearly defined receptor and is generally considered the least potent of the three. Activation by these receptors leads to chemotaxis of neutrophils and monocytes, degranulation of mast cells and basophils with release of histamine, increased vascular permeability, and recruitment of additional inflammatory cells. C5a is typically the most potent and influential anaphylatoxin, playing a central role in directing leukocyte migration and inflammatory cytokine production.

Physiological roles include defense against pathogens and regulation of inflammation. In excessive or dysregulated complement activation, anafilatoxinek contribute to conditions such as sepsis, allergic reactions, asthma, and various autoimmune diseases. Therapeutic approaches targeting these mediators or their receptors, such as C5 inhibitors (e.g., eculizumab) or C5a receptor antagonists (e.g., avacopan), are used to treat certain complement-mediated disorders. Endogenous enzymes like carboxypeptidases inactivate C3a and C5a by removing the C-terminal arginine, reducing their inflammatory activity.