lecture 7 Immunology
Hypersensitivity
Dr. Dalia Galal
Hypersensitive Reactions
1. Type I Hypersensitivity
2. Type II Hypersensitivity
3. Type III Hypersensitivity
4. Type IV Hypersensitivity
1. Basic concepts1. Basic concepts
Hypersensitivity reactions are harmful immune responses , occur when an
individual who has been primed by an antigen, produce tissue injury and
dysfunction.
Allergen : the antigens that give rise to immediate hypersensitivity
Atopy : the genetic predisposition to synthesize inappropriate levels of IgE
specific for external allergens
Types of hypersensitivity : I 、 II 、 III 、 IV
1) 、 Characteristics
2) 、 Components and cells
3) 、 The process and mechanism
4) 、 Common diseases of type I Hypersensitivity
2. 2. Type I hypersensitivity
1) Characteristics
Occur and resolve quickly
Mediated by serum IgE
Systemic and tissue dysfunction
Genetic predisposition
Allergen : pollen 、 dust mite 、 insects etc
selectively activate CD4+Th2 cells and B cells
Allergin ( IgE ) and its production
IgE : mainly produced by mucosal B cells in the lamina prapria
IL-4 is essential to switch B cells to IgE production
High affinity receptor of the IgE on mast cell and basophil
And Eosinophil
2) Components and cells in Type I hypersensitivity
3 The process and mechanism of Type I hypersensitivity
1) Priming stage:last more than half a year
2) Activating stage:
Crosslinkage Enzyme reaction Degranulation of mast cell , basophil
3) Effect stage:
Immediate/early phase response: Mediated by histamine
Start within seconds
Last several hours
Late-phase response : Mediated by new-synthesized lipid mediators
Take up 8-12hours to develop
Last several days
Allergen
Degranulation ,release and synthesis of biological mediators of primed target cells
LOXCOXAcetyl-transferases
Phosphoration of ITAM MAPK
Lipid mediatiors
Endoplasmic reticulum
Degranulation
Myosin
Phosphoration of
Light chain
Cell membrane
Activation of PTK
Phosphatidylcholine
Histamine
Arachidonic acid
Inactivated PKC
ActivatedPKC
Hydroxyl phosphalipid Phosphalipid
The biological mediator on effect stage
1. Histamine:
Dilate blood vessel and Increase vascular permeability
2. Leukotrienes:
Bronchial smooth muscles contract Asthmas
3. Prostaglandin (PGE ):High concentration of PGE Inhibit the secretion of histamine
low concentration of PGE promote the release of histamine
4. Platelet activating factor (PAF) :
Agglutinate and activate platelets to release histamine
5. Eosinophil chemotactic factor ( ECF-A ) :
6. Bradykinin :
Vasodilator function
4. Skin allergy:
4. Common disease of type I hypersensitivity
1. Systemic anaphylaxis: a very dangerous syndrome
1) Anaphylactic drug allergy : penicillin
2) Anaphylactic serum allergy :2. Respiratory allergic diseases :
1) Allergic asthma : acute response, chronic response
2) Allergic rhinitis
3. Gastrointestinal allergic diseases :
The lack of IgA protein hydrolase Undigested protein Allergen
3. 3. Type II Hypersensitivity
1. Characteristic features
2. Mechanism of Type II Hypersensitivity
3. Common diseases of Type II Hypersensitivity
1. Characteristic features
Primed IgG or IgM + Antigen on membrane
Injury and dysfunction of target cells
Allergen
Stimulate Antibody
A. Opsonic phagocytosis
D. ADCC of NK
C. Effect of complement
Combined opsonic activities
Cell injury ways of type II hypersensitivity
Cell
2. Mechanism of Type II hypersentivity
1. Surface antigen on target cells
Target cells: Normal tissue cell, changed or modified self tissue cells
2. Antibody, complement and modified self-cell
Antigen : Blood group antigen, Common antigen,
Self-antigen modified by physical factors or infection
Drug antigen,
Antigen-antibody complex
Activate complement Lyse target cells Opsonic phogacytosis Destroy target cells
Kill the target cellsMacrophage+ 、 Natural killer cells NK 、 + T cells
Stimulating or blocking effect Promote /surpress the target cell funcion
Antigen or hapten on cell
Antibody (IgG, IgM)
Activate complement
Lyse target cell
Opsonic phagocytosis NK , phagocyte Stimulate / block
Destroy target cell ADCC
Target cell injury Change the function ofTarget cell
Mechanism of Type II hypersensitivity
3. Common disease of type II hypersensitivity 1)Transfusion reaction
2) Hemolytic disease of newborn
3) Autoimmune hemolytic anemia and type II drug reaction i. Foreign antigen or hapten Penicillin RBC hemolytic anemia
Quinin Platlet thrombocytopenic purpura
Pyramidone Granulocyte agranulocytosis
ii. Self-antigen
Drug conversion from a hapten to a full antigen
induce self antibody autoimmune hemolytic anemia
4. Type III4. Type III hypersensitivityhypersensitivity
1. Characteristics
2. Mechanism of type III hypersensitivity
3. Common disease of type III hypersensitivity
1 、 characteristics
Free Ag + Primed Ab Larger immune complex
Deposit in tissue or blood vessel wall
Inflammation
2 、 Mechanism of type III hypersensitivity
Formation of the intermediate immune complex
Deposition of the intermediate immune complex
Tissue injury by the immune complex
Soluble antigen Body Antibody
Immune complex
Small molecular soluble Immune complex
intermediate molecular soluble Immune complex
Large molecular insoluble Immune complex
Deposit on the basement of capillaries
Combine and activate complement system
C3a,C5a,C3b
Infiltration of neutrophils
Phagocytose complex
Release the enzymes in lysosome
Tissue injury
Eliminate by phogacytosis
Platelets
Bleeding Edema
Local or systemic immune complex diseases
3. common disease of type III hypersensitivity 1. Local immune complex disease Arthus reaction : Experimental local reaction,
Necrotic vasculitis vasculitis, Ulcer
Human local reaction: insulin-dependent diabetes mellitus (IDDM)
2. Acute systemic immune complex disease serum sickness
antigen (Pinicillin 、 Sulfanilamide ) + Anti-serum Ab+Ag systemic tissue
injury ,fever, arthritis, skin rash
3. Chronic immune complex disease systemic lupus erthymatosus SLE
Rheumatoid arthritis : RF+IgG Deposit on synovial membrane
5. Type IV hypersensitivity 5. Type IV hypersensitivity
1 、 Characteristics of type IV hypersensitivity
2、 Mechanism of type IV hypersensitivity
3 、 Common diseases of type IV
hypersensitivity
1. Characteristics
Interaction of primed T cells and associated antigen
Infiltration of Mononuclear Cells, Inflammatory response
2. Mechanism of type IV hypersensitivity
Formation of effector and memory T cells
Inflammation and cytotoxicity caused by effector T cells
1) Inflammation and tissue injury mediated by CD4+Th1
Release chemokines and cytokines
Immune injury mainly caused by infiltration of mononuclear cells and lymphocytes
2) Cytotoxicity of CD8+CTL
Antigen T cell(CD4+,CD8+)
Secondary contact
Induce
Primed T cell
CD4+ T cell
CD8+ T cell
ReleaseCytokines
IL-2TNF-INF-
TFMCFMIFMAFSRF
Directly kill target cells
Infiltration of monocyte and M
Proliferation of T cell
Exudation and edema
Inflammation characterized by infiltration of M , monocyte, And tissue injury
Mechanism of type IV hypersensitivity
3. Common disease of type IV hypersensitivity
1) Infectious delayed type hypersensitivity
OT( Old Tuberculin ) test
2) Contact dermatitis :
Paint, drug red rash, papula, water blister, dermatitis
3) Acute rejection of allogenic transplantation and
immune response in local tumor mass
Same disease (SLE), multiple immune injury ,hypersensitivity involved
Same drug (penicillin), several types of hypersensitivity