L15: Hypersensitivity Flashcards
Agent and symptoms of Type I hypersensitivity:
IgE
itching, rash, anaphylactic shock
Agent and symptoms of Type II hypersensitivity:
IgM, IgG
massive hemolysis, anemia, kidney failure
Agent and symptoms of Type III hypersensitivity:
IgG
serum sickness, kidney failure
Agent and symptoms of Type IV hypersensitivity:
TDTH, TH1, TC, macrophages
contact dermatitis
Activation of adenyl cyclase produces:
cAMP
Activation of phospholipase C produces:
DAG and PIP2
The release of Ca2+ from the ER has several effects:
a. synthesis of prostaglandins and leukotrienes
b. assembly of microtubules and microfilaments at the cortex
c. fusion of granule (vesicle) with the plasma membrane.
How do you trigger degranulation?
Cross-linking two high affinity receptors bound to the Fc of the IgE with an allergen activates the tyrosine kinases associated on the cytoplasmic sid
What’s released in degranulation?
- Histamine
- prostaglandins
- luekotrienes
- cytokines
Histamine
- increases smooth muscle contraction of intestine and bronchioles
- increases permeability of venules
- increases mucus secretion by goblet cells
prostaglandins
- synthesized after granule release from arachandoic acid
- bronchoconstrictor
leukotrienes
- synthesized after granule release from arachandoic acid
- does everything histamine does only more strongly and longer
cytokines
- promote inflammatory responses by eosinophils and neutrophils
- TNF-α may also induce shock.
Type I clinical conditions include:
- anaphylactic shock
- Allergic rhinitis
- food allergies
- asthma
How does epinephrine work?
reduces vascular permeability, relaxes smooth muscles, increase cardiac output, and raises cAMP levels, blocks further degranulation.
Type II clinical conditions include:
- Blood transfusion mismatches
- Rh incompatibility
- drug-induced hemolytic anemia
Type III clinical conditions include:
- caused by build up of antigen-antibody complexes
- arthritis
- kidney damage
- clotting
- serum sickness
- autoimmune diseases
Type IV clinical conditions include:
- granulomas (like in TB and leprosy)
- contact dermatitis
- graft rejection
Novotny description of Type I:
classical allergy
Novotny description of Type II:
Antibodies target cells for ADCC
Novotny description of Type III:
Excess antibody-antigen complexes
Novotny description of Type IV:
Immune cells target rogue cells
Subsequent response time (once sensitized)-Type I
immediate
Subsequent response time (once sensitized)-Type II
immediate
Subsequent response time (once sensitized)-Type III
immediate
Subsequent response time (once sensitized)-Type IV
1-3 days
mechanism-Type I
IgE activates mast cells and basophils
mechanism-Type II
IgM and IgG attach to cells, attracting non-specific cytotoxic cells
mechanism-Type III
IgG-antibody complexes overwhelm phagocytosis, triggering excess inflammation
mechanism-Type IV
TDTH cells (a type of TH1) signal with cytokines to attack self cells with intracellular pathogen
Cells involved-Type I
Mast cells, basophils, and then responding eosinophils
Cells involved-Type II
NK cells, macrophages, and neutrophils
Cells involved-Type III
neutrophils
Cells involved-Type IV
macrophages and TC cells (not neutrophils)
Pathology results from-Type I
Substances released by degranulation –smooth muscle
contraction
Pathology results from-Type II
Attack on the marked cells by the cytotoxic cells and complement. Red blood cells especially sensitive
Pathology results from-Type III
Clumps of complexes activating complement, releasing anaphylatoxins; damage by neutrophils
Pathology results from-Type IV
Excess damage to healthy tissues by macrophages and TC cells
Diseases- Type I
Hay fever, hives, eczema, food allergies, asthma,
shock
Diseases- Type II
Transfusion reactions, erythroblastosis fetalis, hemolytic anemia
Diseases- Type III
Local – response to insect bites (Arthus), lung irritants. Systemic: serum sickness, kidney damage
Diseases- Type IV
Contact dermatitis, formation of granulomas, graft rejection
Related factoids- Type I
Less likely to occur in people exposed to
farm animals
Related factoids- Type II
Hemolysis leads to kidney damage
Related factoids- Type III
autoimmune disorders(SLE) leading to excess of complexes may trigger this
Related factoids- Type IV
Basis of skin test for tuberculosis
