C5 Antibody (Polyclonal)

C5, is a plasma glycoprotein which is present in normal human serum/plasma at approximately 70 μg/mL, and is key to all complement pathways. C5 is synthesized by a wide variety of cells, including liver hepatocytes, epithelial cells of the genitourinary and intestinal tract, and phagocytic mononuclear cells. The precursor protein to C5 (pro-C5) is a single chain polypeptide which undergoes proteolytic cleavage to yield the circulating form of C5. This circulating form contains 2 disulfide-bonded subunits: α – 115 kD, β – 75 kD, which gives the intact C5 protein an approximate total molecular weight of 190 kD. Activation of the classical or alternative complement pathway results in the assembly of C5 convertase enzymes (C4b,2a,3b and C3b, Bb, C3b) on the target cell surface. Both convertase enzymes cleave C5 into C5a and C5b. C5a is a complement-derived anaphylatoxin. It also expresses potent chemotactic activities for neutrophils and monocytes. C5 can be further cleaved and activated by a variety of non-complement proteolytic enzymes to express C5a-like biological activities without the release of a polypeptide fragment. C5a can also function as an immunoregulator, enhancing both antigen-specific and non-specific antibody response in vitro. C5b remains bound to the C5 convertase on the cell surface. Upon interaction with C6 and C7, a C5b, C6, C7 complex is formed that partially inserts into the cell surface. It subsequently binds C8 and several C9 molecules to form the C5b-9 complex, also known as the Membrane Attack Complex (MAC) which causes irreversible target cell damage. C5 convertase enzymes can be assembled in solution (with cobra venom factor or on particles which do not have a membranous surface and lack a C5b-9 binding site) . In these cases, the C5b-9 complex disassociates from the C5 convertase and combines with S-proteins to form a soluble SC5b-9 complex. This complex has no known membranolytic function.

The anti-human C5 polyclonal antisera was tested against normal human plasma by double immunodiffusion, one-dimensional immunoelectrophoresis, quantitative radial immunodiffusion, and quantitative rocket immunoelectrophoresis. The antiserum was determined to be monospecific for C5 at varying concentrations.