Antibody opsonization
The core receptor + opsonin complex also creates byproducts like C3b and C4b which are important components for the efficient function of the complement system where they can mediate inflammation , such as when C3b binds to C3-convertase , or they can facilitate the formation of the Complement membrane attack complex ( MAC ) by being deposited on the cell surface of the pathogen . 
<triplet> C4b <subj> complement system <obj> part of