Type 3 Hypersensitivity Flashcards
What are immune complexes?
Formed antibody-antigen complexes
How can a type 3 hypersensitivity condition arise?
Due to an antibody reaction occurring against a self or an exogenous antigen.
What happens after the immune complex forms?
The immune complexes are deposited in tissues, where they activate the complement system and cause inflammation.
What must the antigens that form complexes be?
Polyvalent
What occurs in type 2 hypersensitivity that is different to type 3 hypersensitivity?
Antibodies bind to the target that causes inflammation and damage of the target
What occurs in type 3 hypersensitivity that is different to type 2 hypersensitivity?
The antibodies bind to antigens, and it is the antibody-antigen complexes that travel to their target organs where they cause inflammation and damage.
When do the signs and symptoms of type 3 hypersensitivity reaction occur?
4-10 hours after exposure to antigen
What are the 2 forms of a type 3 hypersensitivity reaction?
Serum sickness
Arthus reaction
What is serum sickness?
A systemic illness where immune complexes form in the circulation and are deposited in a widespread fashion throughout many tissues
What is Arthus reaction?
A more localised disorder where complexes are actually formed locally in tissues rather being deposited from the blood
What happens to the antibody-antigen complex?
Opsonisation
Taken up by phagocytes via Fc & complement receptors
What does the pathology in type 3 hypersensitivity reaction due to?
Antigen factors
Host response factors
What are the antigen factors that cause pathology with type 3 hypersensitivity?
chronic persistence of antigen
an abnormal ratio of antigen to antibody
the rate of Ag/Ab formation
What are the host response factors that cause pathology with type 3 hypersensitivity?
antibody defects
complement defects
Fc or phagocyte defects
What is a key example of type 3 hypersensitivity pathology?
Farmers Lung
