Hypersensitivities III Flashcards
1
Q
What is the basic mechanism?
A
Formation of antigen-antibody complexes that activate the complement system and cause tissue damage (involves igG and igM)
2
Q
What happens to the antibody complexes ?
A
they are not targeted at specific tissues, the complexes get stuck in tissues (based on anatomy)
e.g small blood vessels, synovium, glomeruli etc.
3
Q
Why may complexes form and get stuck in vessels?
A
- Ratio of antigen to antibody
- Exhaustion of the phagocytic system
- persistent antigenic stimulation
4
Q
What can occur when the complexes get stuck in vasculature?
A
Acute inflammatory response centred on the vasculature
can result in occlusion of the vessel (thrombosis and infarction)
5
Q
Where are they most likely to lodge and what can they cause?
A
- Lodge in the glomeruli- glomerulonephritis
- Small blood vessels- vasculitis
- synovium (joints)- arthritis
6
Q
What is the arthrus reaction?
A
- antigen is injected, forms local complexes with circulating antibodies
- complement system activated (C3 etc attract mast cells)
- tissue and blood vessel damage occurs
- oedema, hyperaemia, tissue/vascular necrosis can occur
7
Q
What is the timeline of type III hypersensitivity?
A
- Localised reaction soccur within 24 hours of exposure
- Clinical signs begin 1-2 weeks after
8
Q
What are some of the clinical signs?
A
- Urticaria of the skin
- Enlarged lymph nodes/ drainage of inflammatory cells
- joint swelling/ arthritis
- proteinuria
9
Q
A
