ABSTRACT
Complement (C) recognizes potential targets and marks them for clearance and/or lysis and initiates powerful inflammatory reactions. This chapter summarizes the C response to biological targets and clarifies some of the important complement-related issues faced by nanotechnologists as they design next-generation therapeutics. The C cascade is normally held in check on host surfaces by the regulators of C activation (RCA) that inhibit convertase activity and membrane attack complex assembly. C activation is mediated by three major pathways. The classical pathway is triggered by antibody: antigen complexes, and the lectin pathway responds to specific carbohydrate moieties. Prior to the emergence of nanomedicine, numerous clinical procedures were in place that interfaced manufactured materials with biological tissues and/or fluids. Some of the outcomes have relevance to nanomedicine design: Biomaterials generally lack the C regulatory capacity of cells and tissues and in many cases biomaterials have been shown to activate C.
