Changes

#C1 esterase first digests C4 to C4a and C4b and the C2 to C2a and C2b  

#C1 esterase first digests C4 to C4a and C4b and the C2 to C2a and C2b  

#*C4b binds to the antigen

#*C4b binds to the antigen

#C4b then binds C2b

#C4b then binds C2a

#*C4b and C2b complex to form the enzyme C2b¯4b (C3 convertase)

#*C4b and C2a complex to form the enzyme C2a¯4b (C3 convertase)

#C2b¯4b digests C3 into C3a and C3b.

#C2a¯4b digests C3 into C3a and C3b.

#*The production of C3b can now be amplified by the same mechanism as the alternative pathway

#*The production of C3b can now be amplified by the same mechanism as the alternative pathway

#*The binding of one C1q molecule produces one C1 esterase molecule that then causes the binding of many hundreds of C4b¯2b molecules

#*The binding of one C1q molecule produces one C1 esterase molecule that then causes the binding of many hundreds of C4b¯2b molecules

#*Forms C4b2¯b3b (C5 convertase)

#*Forms C4b2¯b3b (C5 convertase)

#*This activates C5 and initiates the [[#Membrane Attack Complex|membrane attack complex]] (MAC)

#*This activates C5 and initiates the [[#Membrane Attack Complex|membrane attack complex]] (MAC)

*All the Ca fragments (C2a, C3a, C4a, C5a)

*Ca fragments C3a, C4a and C5a, and Cb fragment C2b

**Are chemotactic for [[Neutrophils|neutrophils]]  

**Are chemotactic for [[Neutrophils|neutrophils]]  

**Induce acute inflammation

**Induce acute inflammation