Product Description

Rat C3b is derived from native purified rat C3 (CompTech#M113) uponcleavage and release of C3a with the alternative pathway C3 convertase. C3 is central to the activation of all three pathways ofcomplementactivation (Law, S.K.A. and Reid, K.B.M. (1995)). Initiationof each pathwaygenerates proteolytic enzyme complexes (C3convertases) which are bound to thetarget surface. These enzymescleave a peptide bond in C3 releasing theanaphylatoxin C3a andactivating C3b. For a brief time (~60 µs) this nascentC3b is capableof reacting with and covalently coupling to hydroxyl groups onthetarget surface. Carbohydrates are the favored target, but proteinhydroxylsand amino groups also react. This process of tagging thetarget surface withC3b is called opsonization. The reactive site innascent C3b is a thioester(Tack B.J., et al. (1980); Pangburn M.K. andMüllerEberhard H.J. (1980)) andC3b is linked to the target through acovalent ester bond (an amide bond isformed if C3b is attached toamino groups). Most of the C3 activated duringcomplement activationnever attaches to the surface because its thioesterreacts with waterforming fluid phase C3b which is rapidly inactivated byfactors H and Iforming iC3b. Surface-bound C3b is necessary in all three pathwaysforefficient activation of C5 and formation of C5b-9 complexes that lysethetarget cell membrane. Surface-bound C3b and its breakdown productsiC3b and C3dare recognized by numerous receptors on lymphoid andphagocytic cells which usethe C3b ligand to stimulate antigenpresentation to cells of the adaptiveimmune system. The end result isan expansion of target-specific B-cell andT-cell populations.

(For full product description see link...)