Final answer:
C5 convertase of the classical/lectin pathway is C4b2a3b, which is formed when C3b joins C3 convertase (C4b2a). C5 convertase then activates the complement protein C5, leading to the inflammatory response and formation of the MAC to combat invading pathogens.The correct option is D.
Step-by-step explanation:
The C5 convertase of the classical/lectin pathway is C4b2a3b. During the activation of the complement system, C3 convertase (C4b2a for the classical/lectin pathway) splits the C3 molecule into two fragments.
The larger fragment, C3b, combines with C3 convertase to form C5 convertase, which then participates in the subsequent activation of the complement protein C5.
This event continues the cascade that ultimately contributes to the formation of the membrane-attack complex (MAC) and plays a role in the body's inflammatory response and defense against pathogens.
Classical/Lectin Pathway Activation
In the classical pathway, C1 binds to an antigen-antibody complex on an invading pathogen, leading to the splitting of complement components C2 and C4 into two pieces each
The fragments of C4 and C2, namely C4b and C2a, combine to form C3 convertase (C4b2a). When a C3b fragment from a split C3 molecule attaches to C3 convertase (C4b2a), it forms the C5 convertase (C4b2a3b).The correct option is D.