Hypersensitivity Reactions Flashcards
What are hypersensitivity reactions?
They are exaggerated or inappropriate immunological response occurring in response to an antigen.
What is immediate HSR?
They occur within 24 hours of exposure to antigen or allergin
Immediate HSR is predominantly mediated by??
IgG, E, M
Immediate HSR includes?
Type 1, 2, 3
Delayed HSR includes?
Type 4 HSR.
Type 1 HSR is also known as?
Anaphylactic response.
Type 1 HSR is mediated by?
IgE antibodies
Mechanism of action of IgE antibodies.
The antibodies bind to mast cells and basophils which contain histamine granules that are released in the reaction and cause inflammation.
What are the primary principal mediators in type 1 HSR?
Histamine.
Serotonin.
Eosinophil chemotaxis factor.
Neutrophil chemotaxis factor.
Proteases (tryptase, chymase).
What is the function of histamine and Serotonin?
Increases vascular permeability, causes smooth muscle contraction.
What is the function of proteases?
Bronchial mucus secretion
Degradation of basement membrane of blood vessels.
What are the secondary principal mediators for type 1 HSR?
Platlet activation factor
Leukotrienes
Prostaglandins
Bradykinins
Cytokines
What are examples of cytokines?
IL-1 and TNF-ALPHA
IL-4 and 13
What is the function of prostaglandin?
Vasodilation, increase in pulmonary smooth muscle contraction.
What is the function of Bradykinin?
Increased vascular permeability
Pulmonary smooth muscle contraction
What is the function of platelet activation factor?
Platlet activation and degranulation.
What is the function of leukotrienes?
Increase vascular permeability.
What is the function of IL-1 AND TNF-ALPHA?
Systemic anaphylaxis.
What is the function of IL-4 and 13??
Increase IgE production.
What are the common allergens associated with type 1 HSR?
Plant pollen
Proteins - vaccines
Drugs - Penicillin, sulfonamides
Food
Insect products
What are the IgE mediated dxs?
Systemic
Asthma
Allergic conjunctivitis
Skin reactions
Hay fever
Type 2 HSR is mediated by?
Antibodies directed towards antigen present on cell surfaces
What is the mechanism of damage for type 2 HSR?
Opsonisation and complement and fc mediated phagocytosis.
Complement and fc mediated inflammation.
Antibody mediated cellular dysfunction.
What are the examples of autoimmune type 2 HSR?
Autoimmune hemolytic anemia.
Autoimmune thrombocytopenic pupura.
Pemphigus vulgaris.
Non autoimmune type 2 reactions include?
Transfusion reactions.
Erythroblastosis fetalis.
Type 3 HSR is mediated by?
Immune complex diseases.
Type 4 HSR is mediated by?
Direct cellular damage.
What is the mechanism of type 4 HSR?
What is the mechanism of type 3 HSR?
What are the manifestations of type 3 HSR?
Glomerulonephritis
Rheumatoid arthritis
SLE
What are the manifestations of type 4?
Dermatitis
Graft rejection
Leisons
