SC5b-9 (Serum Complement Membrane Attack Complex)

Biological or Clinical Significance:

The terminal complement complex (TCC, SC5b-9) is generated by the assembly of C5b through C9 as a consequence of activation of the complement system by either the classical, lectin, or alternative pathways.  The membrane attack complex (MAC), a form of TCC, is a stable complex that mediates the irreversible target cell membrane damage associated with complement activation.  Complexes formed in the absence of a target membrane bind to naturally occurring regulatory serum proteins, e.g., the S protein, at the C5b-7 stage of assembly forming soluble, non-lytic TCC.  For purposes of this document, we refer to all forms of stable terminal complement complex interchangeably as TCC and SC5b-9, recognizing that other complement regulatory proteins, like clusterin (apolipoprotein J), also form these stable complexes and are detectable in the SC5b-9 Plus assay.

Principle of Test Method:

The SC5b-9 assay is a enzyme immunoassay for the quantification of SC5b-9 complex.

References:

1. Niculescu F, Rus H. The role of complement activation in atherosclerosis. Immunol Res. 2004; 30:73-80.
2. Mollnes TE, Haga HJ, Brun JG, Nielsen EW, Sjöholm A, Sturfeldt G, Mårtensson U. Bergh K, Rekvig OP. Complement activation in patients with systemic lupus erythematosus without nephritis. Rheumatology 1999; 38: 933-940.

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