Hypersensitivity 3 - clinical features and management

Question 1

What is mechansims of type 3 reaction

Answer 1

• excess antigen formation
• Leads to antibody activation and binding
• Leads to immune complex formation which can be deposited locally, in blood vessels, glomeruli or joints
• This causes inflamamtion - activation of complement and neutrophuls
• enzymes released from neutrophils cause damage to basement membrane
• IgG mediated

Question 2

Give an example of a local type 3 reation

Answer 2

farmers lung

• fungal inhalation -> leads to immune complex formation with lungs -> triggers inflammation and leukocyte accumulation

Question 3

What is acute hypersensitivity pneumonitis

Answer 3

• immune complexes being deposited in walls of alvioli and bronchi
• leads to leukocytes accumolation and inflammation within alveoli

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Question 4

what are the clincal features of hypersensitivty pneumonitis

Answer 4

• Wheezing
• Malaise
• Breathlessness
• Dry cough
• Pyrexia
• normal resp examination
• Systemic manifestation

Question 5

what is the managment of type 3 hypersensitivity pneumonitis

Answer 5

• Avoidance
• Corticosteriods - prednisolone
• Immunosuppressants: azathrioprine