Hypersensitivity Types

Question 1

Hypersensitivity is…

Answer 1

a normal immune response that is inappropriately triggered or is excessive

Question 2

Types 1-3 are mediated by…

Answer 2

B cell

Question 3

Type 4 is mediated by…

Answer 3

T cell

Question 4

Type 1

Answer 4

Atopic and anaphylactic.
IgE, immediate hypersensitivity reaction
normally requires multiple allergen exposures
Stimulates mast cells/ basophils which cause histamine release
Symptoms:hives, allergic rhinitis, eczema, asthma, local edema, wheezing. Worst is anaphylaxis.

Question 5

Type 2

Answer 5

cytotoxic, cytolytic, tissue specific
mediated by IgM, or IgG
compliment reaction with macrophages, NK cells, neutrophils and eosinophils.
Can be isoimmunity.
Antigen binding leads to complement fixation.
Antibodies attack antigens on surface of specific cells or tissues.
Often immediate, but can occur over time.
Causes: exposure to antigen or foreign tissue, cells or graft.

Question 6

Type 3

Answer 6

Immune complex
Mediated by IgG
complement (arthus) reaction
Failure of immune and phagocytic systems to eliminate antigen-antibody complexes.
Not immediate rxn or tissue specific.
Causes: persistent infection, autoimmunity
Ex: glomerulonephritis, SLE, vasculitis

Question 7

Type 4

Answer 7

Delayed hypersensitivity
mediated by T lympocytes
No primary antibody
Damage results from delayed celluar reaction to antigen.
Mast cell degranulation, lymphocyte and macrophage invasion.
Onset is slow and long lasting.
Mechanism not totally understood.
Ex: Guillian-Barre disease, TB test, contact dermatitis, MS