Distribution and function of histamine
type of
tissue
effect
clinical
receptor
contraction relaxation manifestation
H1Biblioteka airway smooth muscles +
asthma
alimentary tract muscles +
Plane tree
Castor-oil plant
Dust mite
（2）Ig E antibody and IgE receptor
Th2
Ig heavy chain isotype switching
Levels of Ig E and atopic diseases
IgE and IgE receptors
2. Excitation phase
The same allergen enter the body again→bind to IgE which was bound to mast cells and/or basophils, cross link of FcRI →induction the degranuation of mast cells and basophils, release biological active mediators
Biological active mediators ：
1. preformed mediators：histamine, eosinophil chemotactic factor (ECF), kininogenase , tryptase
2. newly produced mediators: leukotrienes, prostaglandin D2, platelet activating factor, cytokines
Light photomicrograph and Electron micrograph of Mast cell activation
Abul K. abbas et al. Cellular and Molecular Immunology, 7th edition, Elsevier Saunders
I. Type I hypersensitivity（anaphylaxis）
1. The major components （1）allergen
drug, chemical inhalant allergen ：pollens、Dust mite food allergens：nuts, seafood
2. Mechanism of Type I hypersensitivity
Sensitization phase Excitation phase Effector phase
1. Sensitization phase
allergen enter the body
stimulate Ag-specific B cells
differentiated to plasma cells
production of IgE
Bind with high-affinity FcRI which expressed by mast cells
and basophils
Activated mast cell or activated basophil
Hypersensitivity
Guangjie Chen Dept. of Immunology and Microbiology
2015
The Big Bang Theory
Hypersensitivity （allergy）
Hypersensitivity is an inappropriate immune response, which is heightened reactivity to an antigen, such response lead to tissue damage, immunopathology. The various hypersensitivity states were classified into I through IV types by Gell and Coombs. Type I, II and III reactions are mediated by antibodies, whereas type IV reactions are mediated by T cells.
3. Effector phase
Immediate phase—several seconds after contact of allergen, can persist several hours, caused by histamine
Late phase—6-12h after contact of allergen, can persist several days
diarrhea, vomit
vascular endothelial cell +
edema
H2
vascular smooth muscle
+
shock
Biologic effects of mediators of immediate hypersenitivity
Abul K. abbas et al. Cellular and Molecular Immunology, 7th edition, Elsevier Saunders
IgE----Fc RI (ITAM)
Antigen indirectly cross links FcR on mast cells or basophils?
（3）Cells
Mast cell/ basophils: FcεRI eosinophils：express FcεRI after stimulation of IL-5， MCP-3 Cross link Degranulation Release of preformed mediators and newly produced mediators