Complement component C3a (C3a)

Complement component C3a is a 77-amino-acid, highly basic and cationic polypeptide generated by the proteolytic cleavage of the complement protein C3 during complement activation[1][7][5]. C3a is an anaphylatoxin family member, functioning primarily as an immune effector molecule with key roles in both pro-inflammatory and anti-inflammatory signaling. It exerts its biological effects through the G-protein-coupled C3a receptor (C3aR), widely expressed on leukocytes, peripheral tissues, and the central nervous system[1][5][7]. C3a mediates smooth muscle contraction, promotes vascular permeability, triggers mast cell and basophil degranulation, and helps regulate adaptive immune responses, particularly T cell activity and regulatory T cell expansion[1][7][9]. Unlike C5a, it is less potent as a neutrophil activator and chemoattractant. Emerging evidence shows that C3a is involved in tissue regeneration, antimicrobial defense, and modulation of inflammation, sometimes displaying activity opposing C5a[1][4]. Dysregulation of C3a signaling has been implicated in inflammatory, autoimmune, neurodegenerative, and infectious diseases, making it an important therapeutic target and biomarker in clinical immunology[1][7].

Other names

C3a anaphylatoxinAnaphylatoxin C3a

Competitive inhibition of C3a binding to C3aR (preventing receptor activation); Inhibition of C3 cleavage (blocking C3a generation); Neutralization of C3a anaphylatoxin activity