3. Hypersensitivity Flashcards
Type 1 hypersensitivity- Allergy
mediated by IgE
soluble antigen
mast-cell activation
examples: hay-fever, Eczema, Asthma, Urticaria, Anaphylaxis
IgE Receptors
1) FcεRI 2) CD23
Mast cells
Release of granules containing histamine
Mast Cell activation
IgE secreted by plasma cells binds to a high-affinity Fc receptor FcεRI on mast cells
Activated mast cells secrete signals to B cells
this stimulates IgE production
Histamine
dilates small blood vessels
bound to proteoglycans
stored in secretory vesicles
Type II Hypersensitivity
Mediated by IgG
Cell or matrix associated
destruction of rbcs or platelets
haemolytic anaemia, thrombocytopenia
Type III Hypersensitivity
Mediated by IgG
Soluble antigen
Effector mechanism: complement, phagocytes
Examples: arthus reaction, serum sickness
Type IV Hypersensitivity
mediated by TH1 cells
soluble antigen
macrophage activation
examples:
1) Delayed-type hypersensitivity
2) Contact hypersensitivity
3) celiac disease
Delayed-type Hypersensitivity
antigen = proteins
consequence = Local skin swelling
Contact Hypersensitivity
antigen = haptens
consequence = Local epidermal reaction
eg:Poison ivy contact dermatitis
Celiac disease
antigen = gliadin
consequence = villous atrophy in small bowel, malabsorption
