Acute phase proteins

Question 1

What are acute phase proteins?

Answer 1

proteins that are made in the liver

Increase their concentration by more than 25% during inflammation

Question 2

Where can we find acute phase proteins?

Answer 2

Blood plasma

Question 3

Where do they come from?

Answer 3

The liver

IL-1, IL-6 & TNF-α stimulate the hepatocytes to produce the acute phase reactants

Question 4

How do acute phase proteins reflect inflammation?

Answer 4

Acute phase proteins are a result’ of inflammation

During inflammation, their levels will increase, especially C reactive protein – they aid the body’s immune response.

Inflammation will cause levels of acute phase proteins to increase, & levels of albumin to decrease.

Question 5

What are the different types of acute phase protein? What do each do? i.e. main functions

Answer 5

C-reactive protein:
1. Dilation of arterioles - increases blood flow & speed of arrival of immune cells.
2. Stimulates mast cells to release histamine - which opens up the endothelium to allow other immune cells access to the infection.
3. Cause chemotaxis of phagocytes.
4. Opsonisation of microbes – marks cells for destruction (like a flag) & increases the affinity of phagocytes for binding to pathogen.
5. Stimulates cytokine production- by binding to Fc receptors on monocytes and neutrophils.
6. Activates complement system - allows membrane attack complexes to be formed.

C3:
- A component of the complement cascade.
- Gets activated by the classic and alternative pathways.
- Activates the membrane attack complex C5b & C6/7/8/9
- Can directly act in the process of inflammation by:
- Dilating arterioles
- Stimulating mast cells to release histamine
- Cause chemotaxis of phagocytes
- Opsonisation of microbes

Serum amyloid A:
- Appears to have chemotactic effects - involved in chemotaxis
- Involved in resolution of the inflammatory response.

Haptoglobin:
- Binds free haem that has come about due to intravascular haemolysis (breakdown of RBCs).

Fibrinogen:
- Produces fibrin clots w/ the help of thrombin.
- Can activatebridgesbetween platelets through binding to GP2B/3Areceptors found on platelets.