Hypersensitivity Flashcards
Which type of hypersensitivity reaction is responsible for most allergic reactions?
Type I Hypersensitivity
Give five examples of clinical manifestations of type I hypersensitivity
Allergic rhinoconjunctivitis Asthma Eczema/urticaria Food allergy Anaphylaxis
What mediates type I hypersensitivity?
IgE antibodies
Also: mast cells, basophils, eosinophils, T-helper2 cells
Which type of hypersensitivity reaction is responsible for most tissue-specific cytotoxic reactions?
Type II Hypersensitivity
Give four examples of type II hypersensitivity reactions
Haemolytic reaction following blood transfusion (ABO, Rhesus incompatibility)
Haemolytic disease of the newborn
Hyperacute graft rejection
Organ-specific autoimmune disease
Give four autoimmune diseases that are caused by type II hypersensitivity reaction
Graves disease
Myasthenia gravis
Goodpasture’s syndrome
Pemphigus (skin blisters)
What mediates type II hypersensitivity reactions?
IgG or IgM antibodies
Which type of hypersensitivity reaction involves the abnormal deposition of formed antibody-antigen complexes in tissues?
Type III Hypersensitivity
Give six examples of diseases caused by type III hypersensitivity
Systemic Lupus Erythematosus
Serum sickness
Extrinsic allergic alveolitis (e.g. farmer’s lung)
Chronic infection (e.g. leprosy, malaria)
Post-strep glomerulonephritis
Tumours
What are the main mediators of type III hypersensitivity?
Antibodies
- immune complexes involving soluble antigens
Which type of hypersensitivity reaction takes at least 48 hours to manifest itself?
Type IV Hypersensitivity
- aka delayed hypersensitivity
Give five examples of diseases caused by type IV hypersensitivity
Mycobacteria infection (tuberculosis) Type 1 Diabetes Mellitus Multiple sclerosis Rheumatoid arthritis Contact dermatitis
What mediates type IV hypersensitivity?
T-helper cells Th1 and Th17
Also the cytokines secreted by Th cells
What type of antigens trigger type IV hypersensitivity reactions?
Haptens (low molecular weight agent)
+ Carrier (host protein that attaches to the hapten to provide sufficient antigenic bulk)
What are the three phases of a type I hypersensitivity reaction?
- sensitisation
2a. early phase response
2b. late phase response