Classical Cascade

In a simplified way, the classical cascade occurs as follows:
ag.ab reaction -Cl-4-2-3-5-6-7-8-9. This can be described in detail as follows:

1. Ag*Ab --> Clqrs complex (in the presence of free Ca⁺⁺)

2. Cls activates C4b*C2a complex to attach to the rbc membrane in the presence of free Mg⁺⁺.

3. C4b*C2a (C3 convertase) causes C3b (100's of molecules) to attach to the rbc.

4. C5b --> C6 --> C7 --> C8 --> C9~~ (hemolysis)

~ Detected in indirect antiglobulin tests (IATs) if polyspecific AHG is used

~~ Detected in sal. 37°C tests

Classical Cascade