The C4a2b functions as a C3 convertase that can subsequently cleave hundreds of molecules of C3 into C3a and C3b. Much of the C3b binds to adjacent proteins and carbohydrates on the antigen to participate in opsonization while C3a can stimulate inflammatory responses. Some of the C3b binds to C4b2a to form C4b2a3b, a C5 convertase that can cleave C5 into C5a and C5b.