Allergy, hypersensitivity and the lung Flashcards
how many types of hypersensitivity reactions?
4
5 main differet types of antibodies? function of each?
IgM: pentamic structure, produced early in immune response
IgG: monomeric structure, most common in circulating blood and tissue and more abundant secondary response
IgE: monomeric, Likely to have developed in response to parasitic threats. Implicated in allergy, particularly alongside eosinophils
IgA: dimeric, Expressed in mucosal areas such as the GI, respiratory and urinary tracts. It is also secreted in saliva, tears and breast milk.
IgD: Monomers, induction of antibodies in B cells, activates basophils and mast cells
MAGED
Type I hypersensitivity reaction: time taken? mediated by? leads to? example
Immediate reaction mediated by IgE antibodies which bind to mast cells and basophills causing ‘sensitivity’ to that antigen. When this antigen is encountered again, it will cause cross-linking of the bound IgE and degranulation of mast cells and basophils to release histamines.
E.g. leads to allergy, anaphylaxis, atopic disease.
Type II hypersensitivity reaction: time taken? mediated by? what occurs? give an example?
gG or IgM antibody bind to antigen on host membrane in cytotoxic reaction; occurs in hours to days; examples include haemolytic disease of the newborn, autoimmune haemolytic anaemia, Goodpasture’s syndrome/Anti Glomerular Basement Membrane Disease (aGBM)
e.g. Anti Glomerular Basement Membrane Disease (aGBM)- autoimmune disease causing antibodies against type IV collagen in alveoli and glomeruli; presents with haemoptysis, renal dysfunction; treated with steroids, plasmapheresis, cyclophosphamide.
Type III hypersensitivity reaction: time taken? mediated by? what occurs? give an example?
antigen-antibody immune complex-mediated reaction; occurs over hours, days, or weeks; examples include serum sickness, Rhematoid Athritis, SLE, post-streptococcal glomerulonephritis;
e.g. hypersensitivity pneumonitis- Acute, sub acute and chronic forms (fibrotic, non fibrotic), Normally IgG response
Type IV: time taken? mediated by? what occurs? give an example?
delayed hypersensitivity (24-72 hours); antigen is exposed to APC and activates T cell. These complexes trigger the classical complement pathway, leading to the recruitment of inflammatory cells
involved in contact dermatitis and tuberculin skin test; causes local tissue inflammation and damage.
e.g. sarcoidosis- patches of swollen tissue, called granulomas, form in organs
how does someone become hypersensitive?
There can be several factors that lead an individual to develop hypersensitivity. There may be a genetic susceptibility to these reactions or a triggering event of another kind on the immune system such as an infection.
