IMMUNOLOGY

Detailed explanation-1: -The molecules of C3b that bind the C3 convertase itself initiate the late events, binding C5 to make it susceptible to cleavage by C2b or Bb. The larger C5b fragment triggers the assembly of a membrane-attack complex, which can result in the lysis of certain pathogens.

Detailed explanation-2: -When the density of C3b molecules on the cell surface becomes sufficiently high, the existing C3 convertases (C4b2a and C3bBb) gain the ability to cleave C5, leading to formation of C5a and C5b (Figures 1A, B) (7, 8). Figure 1. Complement convertases mediate C3 and C5 conversion.