Properdin system

From Biology-Online Dictionary | Biology-Online Dictionary

properdin system

An immunological system that is the alternative pathway for complement, composed of several distinct proteins that react in a serial manner and activate C3 (third component of complement), seemingly without utilizing components C1, C4, and C2; in addition to properdin, the system includes properdin factors A (native C3), B (c3 proactivator), D (c3 proactivator convertase), and perhaps at least one other, E; the system can be activated, in the absence of specific antibody, by bacterial endotoxins, by a variety of polysaccharides and lipopolysaccharides, and by a component of cobra venom.