Monoclonal antibody 2942 reacts with a neo-epitope on human C5a/C5a des-Arg that is formed by proteolytic cleavage of C5 into C5a and C5b during complement activation. C5a is a single chain glycopeptide composed of 74-amino-acids, which is rapidly converted to the less potent derivate C5a des-Arg upon removal of the C-terminal arginine by carboxypeptidase B. C5a acts as a potent anaphylatoxin by binding to its high affinity receptor C5aR (or CD88) on the membrane of target cells inducing smooth muscle contraction, increased vascular permeability, degranulation of mast cells and basophils, and the release of lysosomal enzymes. In addition C5a stimulates the directed migration of neutrophils, eosinophils, basophils and monocytes.
C5a is involved in inflammatory reactions seen in gram-negative bacterial sepsis, trauma, ischemic heart disease, post-dialysis syndrome and a variety of autoimmune diseases. Elevation of C5a is associated with increased cardiovascular risk in patients with advanced atherosclerosis. Also, C5a is closely associated with the capillary leak syndrome in leukemic children after bone marrow transplantation. C5a is also a marker in urine for predicting the onset of acute graft rejection after kidney transplantation and has been shown to be present in extracellular deposits in patients suffering from age-related macular degeneration (AMD).