The Complement System. Flashcards
What are complement proteins?
Specialised proteins that can be activated by the innate or acquired immune system.
What are the 3 main tasks that are carried out by the complement system?
Cell lysis.
Chemotaxis.
Opsonisation.
Do complement proteins require antibodies in order to work?
No.
Will complement proteins interact with antibodies?
Yes.
Are there cells involved in the complement system?
No, there are no cells involved in the complement system.
Are complement proteins part of the innate or adaptive immune system?
The innate immune system, but they have interactions with the acquired immune system.
How many different complement proteins are there?
Around 20.
What 2 cells can synthesise complement proteins?
Macrophages.
Hepatocytes.
What will complement proteins exist as in the blood?
They exist as zymogens until they are activated.
How are inactive complement proteins activated?
Via proteolytic cleavage.
What names are used to designate different complement proteins?
A letter and a number.
E.g. C1, C2, C3.
Can complement proteins kill cells, bacteria, viruses and parasites?
Yes.
Will complement proteins interact with antibodies to kill pathogens?
They can kill pathogens with or without antibodies.
What is one way that complement proteins will kill pathogens?
They can coat the pathogen and this marks it for phagocytosis.
This process is called opsonisation.
Are complement proteins able to perform opsonisation?
Yes.
Are complement proteins able to induce inflammation?
Yes.
What are 2 ways that complement proteins can induce inflammation?
By attracting immune cells via chemotaxis.
By increasing vascular permeability and smooth muscle contraction.
What is a common immune protein that complement proteins will interact with?
They promote the degranulation of mast cells.
What are the 5 major functions of complement proteins?
The clearing of immune complexes.
Promotion of the degranulation of mast cells.
Induction of inflammation.
Opsonisation.
Killing of pathogens.
What are immune complexes?
Complexes formed when an antibody binds to an antigen
How does a complement protein perform opsonisation?
The protein binds to a bacterium and this marks the cell for phagocytosis.
What region of an antibody will complement proteins bind to?
The FC region.
Can complement proteins bind to an antibody that is already bound to a pathogen?
Yes, as they bind to the FC region. It is the variable region that pathogens bind to.
What happens when a complement protein binds to an antibody that is already bound to a pathogen?
It leads to lysis of the cell or a phagocyte will come and consume the cell.
