Osmotic lysis, complement

Figure 1.14. Complement activation via the classical pathway. The sequential activation of complement following antibody deposition onto a surface is shown. C9 forms a pore in the membrane, eventually leading to cell death by osmotic lysis. See text for details.

For complement-dependent cytotoxicity, a complex cascade of protein binding and cleavage occurs that culminates in final complement mediated effector functions of phagocytosis, recruitment and activation of leukocytes, and osmotic lysis. It has been reported that Rituximab (anti-CD20) utilizes a complement-dependent mechanism for tumor cell destruction [14], If the desired effect of a therapeutic antibody is complement-dependent activity, the isotype subgroup chosen should be one that binds to complement proteins (IgGl or IgG3). 

The membrane-attack complex (MAC) is the cytolytic end product of the complement cascade it forms a transmembrane channel, leading to osmotic lysis of the target cell (Fignre 15.1). 

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