Changes

#** C4b and C2b complex to form the enzyme C2b¯4b.

#** C4b and C2b complex to form the enzyme C2b¯4b.

# C2b¯4b digests of C3 into C3a and C3b.  

# C2b¯4b digests of 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 cause the binding of many hundreds of C molecules. The C3b molecule that is produced by the action of this enzyme can also bind to it, forming the complex enzyme C , which is the second enzyme capable of activating C5 and initiating the MAC. Like the alternative pathway, the major effects of classical pathway activation are to produce iC3b and hence it promotes phagocytosis and initiates inflammation.

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

. All the Ca fragments (C2a, C3a, C4a, C5a) are chemotactic for neutrophils and are potent inducers of acute inflammation (they are termed the anaphylotoxins).  

#* The C3b molecule that is produced by the action of this enzyme can also bind to it.

*# '''The binding of soluble lectins to pathogens'''.

#*** This activates C5 and initiates the MAC.  

* Like the alternative pathway, the major effects of classical pathway activation are to produce iC3b.

*** Promotes phagocytosis and initiates inflammation.

* All the Ca fragments (C2a, C3a, C4a, C5a) are chemotactic for neutrophils and induce of acute inflammation.  

 

====The binding of soluble lectins to pathogens====

*#* E.g. collectins.

*#* E.g. collectins.

*#* Lectins are proteins that bind carbohydrates, in this case carbohydrates that have a terminal mannose residue – they are called mannose-binding lectins and are secreted by the liver into plasma. This action of lectin binding to carbohydrate activates plasma-associated proteases called mannose-binding lectin associated proteases (MASPs), these act on C4 and C2 in the same way as C1 esterase.

*#* Lectins are proteins that bind carbohydrates, in this case carbohydrates that have a terminal mannose residue – they are called mannose-binding lectins and are secreted by the liver into plasma. This action of lectin binding to carbohydrate activates plasma-associated proteases called mannose-binding lectin associated proteases (MASPs), these act on C4 and C2 in the same way as C1 esterase.