Complement component C8 alpha chain (C8A)

Complement component C8 alpha chain (C8A) is one of three genetically distinct subunits (alpha, beta, and gamma) that form complement component 8, a critical part of the membrane attack complex (MAC) in the complement system[1][2]. The complement system is a group of proteins that helps mediate immune responses such as lysis of pathogens, inflammation, and clearance of immune complexes[2][3]. C8A, together with C8B and C8G, interacts with other complement proteins (C5b, C6, C7, C9) to assemble the MAC, which forms a pore in the membrane of target (usually bacterial) cells, causing cell lysis[1][3][4]. C8A is required for MAC function; mutations in the C8A gene can lead to complement component 8 deficiency, increasing susceptibility particularly to Neisseria bacterial infections[2]. The protein contains a membrane attack complex/perforin (MACPF) domain, is found in the extracellular region and membrane-associated complexes, and does not act as a receptor, enzyme, or transporter, but as an effector in immune lysis[1][3][4].

Other names

C8 alpha chainC8AComplement C8AComplement component 8 alpha chain

Drugs or inhibitors of complement generally act by preventing assembly of the membrane attack complex at the level of C5, C6, C7, C8, or C9, thereby blocking pore formation and subsequent cell lysis. CD59 (a protein) binds to C8A and C9 to inhibit MAC assembly[1].