The Complement Cascade. Flashcards
What are the 2 pathways that lead to the activation of the compliment system?
The alternative (natural) pathway.
The classical (specific) pathway.
How does the alternative pathway activate the complement system?
There is contact with a microbial surface.
Is the alternative pathway of the complement system part of the innate or adaptive immune system?
The innate immune system.
How does the classical pathway activate the complement system?
Via interactions with antibodies IgG or IgM.
Is the classical pathway of the complement system part of the innate or adaptive immune system?
It interacts with both the classical and innate immune systems.
When will IGG or IGM antibodies be produced?
During almost any immune response.
Will the classical pathway activate the complement system if it is fighting a pathogen that is new to the body?
No, as antibodies cannot be made.
Does the alternative pathway need antibodies to activate the complement system?
No.
When is the alternative pathway of the complement system active?
It is always active at low levels, but during infections it is up-regulated.
Are there any cellular responses in the alternative pathway of the complement system?
No.
The lectin pathway is part of what aspect of the complement system?
The alternative pathway.
How can the lectin pathway be activated by mannose?
When serum lectins from the host bind to mannose on a bacterial cell wall.
What are mannose binding lectins?
Serum lectins that bind to mannose.
Why can mannose binding lectins activate the alternative pathway of the complement system?
As mannose binding lectin is very similar to C1q which is the enzyme that activates the complement cascade.
What are lectins?
A part of the innate immune system and they will always bind to carbohydrates.
What activates the classical pathway of the complement system?
Antibodies which are either IgG or IgM.
What region of the antibody binds to a pathogen?
The FAB region.
What happens in the classical pathway once the antibody has bound to a pathogen and a complement protein?
The antibody activates the compliment protein.
The complement protein disables or kills the microbe.
A complement protein binds to what part of an antibody?
The FC part.
Will IGG or IGM be better at activating the classical pathway of the complement system?
IgM is much more efficient at activating the pathway.
Why is IGM much more effective at activating the classical pathway of the complement system?
As there must be 2 IgG molecules present to activate the compliment system.
How does an IGM or 2 IGG antibodies activate the classical pathway of the complement system?
They bind to the C1 complex which is the complement protein.
What happens in the classical pathway of the complement system when an IGM or 2 IGG antibodies bind to the C1 complex?
Other compliment proteins can bind to C1.
What happens when the complement proteins bind to the C1 complex?
The destruction or opsonisation of the microbe can take place.
