week 2 Flashcards
what is the principle cause of type 1 hypersensitivity - e.g. asthma , ecxema, hayfever
IgE mediated, it is atopic .
characteristics of type 1 hypersensitivity
response to challenge occurs immediately
tends to increase in severity with repeated challenge
predominantly mediated by IgE bound to mast cells
Process of allergy
-Sensitisation Mast cells primed with IgE -Re-exposure to antigen -Antigen binds to IgE associated with mast cells -Mast cells degranulate releasing: Toxins (i.e. histamine) Tryptase Pro-inflammatory cytokines Chemokines Prostaglandins Leukotrienes Pro-imflammatory process stimulates and amplifies future responses
tissue effects from early phase of type hypersensitivity
occurs within mins of exposure to antigen
occurs largely as a result of histamine and prostaglandins - smooth muscle contraction and - increased vascular permeability
tissue effects from late phase of type 1 hypersensitivity
occurs over hours to days after exposure to antigen
principally mediated through recruitment of T cells and other immune cells to site
results in
- sustained smooth muscle contraction/hypertrophy
- tissue remodelling
what is anaphylaxis
severe systemic type 1 hypersensitivity . can be rapidly fatal.
- widespread mast cell degranulation caused by systemic exposure to antigen.
- vascular permeability is principle immediate danger : soft tissue swelling threatens airway ; loss of circulatory volume causing shock
type 2 hypersensitivity caused by …
binding of antibodies directed against human cells - IgG usual cause .
it is a common cause of autoimmune diseases
type 2 hypersensitivity reaction
- sensitisation
- opsonisation of cells
- cytotoxicity ; complement activation , inflammation, tissue destruction
- (in some cases)- direct biological activation with antigen - i.e receptor activation impaired enzyme action)
type 3 hypersensitivity is mediated by?
immune complexes bound to soluble antigen - its a cause of autoimmune disease and drug allergy
how do the complexes bound to soluble antigens form in type 3 hypersens?
aggregate in small blood vessels ; - direct occlusion
- complement activation
- perivascular inflammation
what is type 4 hypersensitivity is mediated
by the action of lymphocytes infiltrating area
what is type 4 hypersensitivity also known as
delayed type hypersensitivity
- presents several days after exposure
what is an autoimmune disease
harmful inflammatory response directed against ‘self’ tissue by the adaptive immune response
- organ specific / systemic
type 1 diabetes
selective autoimmune destruction of the pancreatic beta cells (often a mix of type ii and iv)
- causes profound insulin deficiency and death if not treated with insulin replacement
- inflammation of the islets of Langerhans precedes symptoms by many years
What is myasthenia gravis
syndrome of fatigable muscle weakness .
caused by IgG against acetylcholine receptor
antibody blocks receptor and prevents signal transduction
