Hypersensitivity II (IMMUNOLOGY) Flashcards
What is the pathophysiology behind a type II hypersensitivity reaction?
Antibody binds to cell-surface antigen resulting in activation of complement and opsonisation leading to cell lysis and antibody-mediated phagocytosis
What are the 4 effects of complement activation?
Chemotaxis
Solubilisation of immune complexes
Direct killing via membrane attack complex
Opsonisation
In a type II hypersensitivity reaction B cells produce …
antibody directed against cell membrane protein
What does binding of antibody to cell surface antigen result in?
complement activation
NK and Eosinophil activation and ADCC
Act as opsonin for phagocytes
What are examples of type II hypersensitivity in blood cells and to what do the antibodies bind?
Transfusion reactions
Autoimmune haemolytic anaemia (bind to red cells)
Idiopathic thrombocytopaenic purport (antibodies bind to platelets)
What is an example of a type II hypersensitivity in the kidneys and what do the antibodies bind to?
Good pasture’s syndrome
bind to glomerular basement membrane
What are examples of type II hypersensitivity in the nervous system and what do the antibodies bind to ?
Myasthenia graves (bid to acetyl choline receptor) Gillan-Barre-Syndrome (bind to peripheral nerve glycoprotein)
What is an example of type II hypersensitivity in the endocrine system and what do the antibodies bind to?
Grave’s disease (antibodies bind to TSH receptors)
What is an example of type II hypersensitivity in the skin and what do the antibodies bind to?
Pemphigus vulgaris (antibodies bind to epithelial cell cement)
What happens as a result of an incorrect blood transfusion?
Complement-mediated lysis of transfused red blood cells will begin after as little as 1 ml of blood is transfused
What are the clinical features of transfusion reactions?
Pyrexia Rigors Tachycardia Tachypnoea Hypotension Dizziness Headaches Chest or lumber pain Possibly fatal
What is the consequence of Grave’s disease?
Hyperthyroidism
What released TSH (thyroid stimulating hormone)?
Pituitary gland
Many type II hypersensitivity reactions are mediated by ….?
auto-antibodies
What are the two management methods of type II hypersensitivity?
Plasmapheresis
Immunosuppression
What does plasmapheresis aim to do?
Remove all pathogenic antibodies
How does plasmapheresis work?
Remove patient blood via cell separator
Replace cellular contents (plasma replaced by someone else’s)
What limits the efficacy of plasmapheresis?
rebound antibody production
Immunosuppressants switch off …?
B cell production of antibody
What is the pathophysiology behind a type III hypersensitivity reaction?
If there’s excess soluble antigen, antibody binds & forms small immune complexes that are trapped in small blood vessels, joints & glomeruli
Farmer’s lung is an example of which type of hypersensitivity reaction?
III
Which organisms cause Farmer’s lung?
Aspergillus fumigatus Micropolyspora faeni Avian serum proteins Aspergillus clavatus A
Which agent causes Bird fancier’s lung?
Avian serum proteins
Which organism causes Malt worker’s lung?
Aspergillus clavatus
Which organism causes Cheese worker’s lung?
Apergillus cravats
Penicillin casei
Which organism causes Maple bark stripper’s lung?
Cryptostroma cotricale
What occurs in acute hypersensitivity pneumonitis?
Immune complexes deposited in the walls alveoli and bronchioles causing leukocyte accumulation and inflammation within alveoli
What are the symptoms associated acute hypersensitivity pneumonitis`
Wheezing and malaise after 4-8 hours after exposure to antigen
May be associated with dry cough, pyrexia, breathlessness
O/E often normal
How can type II hypersensitivity reactions be diagnosed?
Specific IgG antibody testing that are reactive to putative antigens
How can type III hypersensitivity reactions be managed?
(Avoidance)
Corticosteroids
Immunosuppressants
What is the pathophysiology behind type IV hypersensitivity reactions?
Initial sensitisation to antigen generates primed effector TH1 cells
Second exposure - activation of primed T cells - recruitment of macrophages, neutrophils and other lymphocytes - release of proteolytic enzymes - persistent inflammation
Poison ivy and sarcoidosis are examples of which type of hypersensitivity reaction?
Type IV
Why is sarcoidosis treated with systemic corticosteroids?
Block T cell activation & macrophage activation
