Hypersensitivity reactions Flashcards
What is a hypersensitivity reaction?
Antigen-specific immune responses that are either inappropriate or excessive and result in harm to the host
Name 2 intrinsic agents
Infectious microbes (mimicry) and self antigens (auto-immunity)
What are the 4 types of sensitivity reaction?
Allergy, antibody mediated, immune complex mediated, cell mediated(delayed)
Which Immunoglobulin is a type 1 reaction?
IgE
Which immunoglobulin is a type 2 reaction?
IgG (sometimes IgM)
What is the sensitisation phase?
First encounter with an antigen, activation of APCs and memory effector cells. After this the individual is “sensitised”
What does a type 2 sensitivity reaction target?
Cell bound antigens
What is haemolytic disease of the newborn?
When the mother is Rhesus -ve and the fetus is rhesus +ve, the mother develops antibodies that wil cross the placenta and damage fetal red blood cells. (only of a further child, not the first)
What medication is given in myasthenia gravis?
Pyridostigmine (AChE inhibitor)
What is plasmapheresis therapy?
Plasma is separated from blood and harmful antibodies removed, for short term relief and allows healing of damaged tissue
What does a type 3 reaction target?
Soluble antigens
How is tissue damage caused in a type 3 reaction?
Deposition of immune complexes
Which type of immune complex is most difficult to remove?
Intermediate
Small= removed by macrophages
Large= removed by opsinisation
What diseases are caused by type 3 hypersensitivity reactions?
Rheumatoid arthritis, glomerulonephritis, systemic lupus erythematous
What diseases are caused by type 4 hypersensitivity reactions?
Contact hypersensitivity, granulomatous sensitivity, Hashimotos disease
Give some examples of allergens?
Tree and grass pollen, house dust mite, fungal spores, insect venom, medicines, foods
What is the abnormal adaptive immune response in type 1 reactions?
TH-2 response with IgE, normally a TH-1 response with IgG. Mast cells are activated
What is the hygiene hypothesis?
Children exposed to animals and microbes in the early postnatal period appear to be protected against certain allergic diseases
What is the old friend hypothesis?
Western lifestyle induces alteration of the symbiotic relationships with parasite and bacteria leading to alterations of the microbiome
What can be measured for anaphylactic shock?
Tryptase
What are the signs and symptoms of systemic mast cell activation?
Hypotension, cardiovascular collapse, angioedema, breathing problems
What does there have to be for it t be anahylaxis?
Acute onset, rapidly progressing, skin and another system. If known to have anaphylactic reaction skin doesn’t have to be involved
