Hypersensitivity diseases Flashcards
Type I sensitivity also known as:
anaphylaxis
Type I associated with which antibody?
IgE
What are the IgE complex-induced mediators in anaphylactic shock?
- histamine
- leukotrienes
- TNF-alpha
- IL-1
- IL-6
- serotonin
- bradykinin
- platelet activating factor (PAF)
What do IgE complex-induced mediators do?
- contract smooth muscle
- increase vascular permeability
- ## induce hypotension
Common inducers of IgE and anaphylactic shock:
- venom
- foods
- drugs
- antibiotics like penicillin
Urticaria is associated with which type of hypersensitivity?
Type I
What is urticaria?
- cutaneous form of type I
- IgE mediated
- wheal and flare lesion and pruritis
asthma is associated with which type of hypersensitivity?
Type I
Cells involved in asthma inflammation:
- mast cells
- Th2 CD4+ cells
- basophils
- eosinophils
Asthma - important mediators
- leukotrienes
- PAF
- eosinophil chemotactic factor (ECF)
- histamine
Asthma - important triggers
- resp infections
- environmental pollutants
- aspirin
- NSAIDs
extrinsic vs intrinsic asthma
extrinsic - associated with allergens and pollutants
intrinsic - can be non-immunologic (cold, exercise)
rhinitis associated with which type of hypersensitivity?
Type I
rhinitis associated with which antibody type?
IgE
cytokine mediators associated with rhinitis:
- histamine
- leukotrienes
- prostaglandin D2
- ECF
Explain the therapeutic induction of a hyposensitive state in an allergic individual
- repeated injection of the agent in subliminal doses
- Increased IgG blocks IgE binding and reduces reaction-associated mediator release
Type II hypersensitivity is also known as:
Cellular antigen-antibody cytotoxicity
briefly explain type II hypersensitivity:
antibodies are directed against epitopes that occur on the cellular surface membranes of organs and tissues
Explain how damage occurs in type II hypersensitivity:
1) lytic action of complement
2) opsonization by phagocytic cells
3) killing by ADCC
4) killing of target cell by Tc cells or NK cells or both via perforins and serine proteases (granzymes)
transfusion reactions are associated with which type of hypersensitivity?
Type II
What is the most common type of transfusion reaction?
ABO reaction
What is the most severe type of transfusion reaction?
Rh reaction
What test can be used to test for the presence of anti-Rh IgG antibody in mother’s circulation or in fetal cells?
Coombs test
Those with an O blood phenotype have antibodies against:
Can accept:
against: A and B blood
can accept: O only
Those with an A blood phenotype have antibodies against:
Can accept:
against: B blood
can accept: AA or AO
Those with B blood phenotype have antibodies against:
Can accept:
against: A blood
Can accept: BB or BO
Those with AB blood phenotype have antibodies against:
Can accept:
against: neither
Can accept: Anything
What does the + or - stand for in A- or A+ blood?
+ means presence of Rh protein
Erythroblastic fetalis is associated with which type of hypersensitivity?
Type II
autoimmune reactions are associated with which type of hypersensitivity?
Type II
Goodpasture’s syndrome is an example of:
autoimmune reaction (type II)
What is the mechanism of Goodpasture’s syndrome?
- reactivity against self glycoprotein present on glomerular basement membrane
- IgG binds antigenic glycoprotein, activates complement
- C5a attracts neutrophils which release lysosomal enzymes and kill glomeruli
What does most of the damage in Type III hypersensitivity reactions?
Neutrophils attracted by C5a release lysosomal enzymes that destroy tissue
Type III hypersensitivity reactions are also known as:
antigen-antibody complex reactions
What do antigen-antibody complexes secrete?
C5a, anaphylatoxins, clotting factors
Briefly explain type III hypersensitivity reactions:
antibody binds antigen in complexes and evades phagocytosis. Deposits in tissues or on blood vessel surfaces and secretes chemotactic mediators leading to neutrophil destruction of tissues.
Serum sickness is associated with which type of hypersensitivity reaction?
Type III
Polyarteritis nodosa (PAN) is associated with which type of hypersensitivity reaction?
Type III
Describe polyarteritis nodosa:
- constant insult to arterial walls by circulating ag-ab complexes
- thrombosis common
Systemic lupus erythematosus (SLE) is associated with which type of hypersensitivity reaction?
Type III
If lupus involves loss of self tolerance, why isn’t it considered an autoimmune disease classified as type II?
The expected initiator of lupus is an antibody response against bacterial or viral DNA. The mechanism for loss of self-tolerance is unknown.
What distinguishes Masugi (Goodpasture’s) glomerulonephritis from lupus glomerulonephritis?
In fluorescent test, Masugi ag-ab complexes are uniformly dispersed, indicating a reaction to a host antigen with genetic origin. In lupus, ag-ab complexes are clumped, indicating they collected in certain locations from circulation.
Rheumatoid arthritis is associated with which type of hypersensitivity reaction?
Type III
Briefly describe the mechanism of rheumatoid arthritis:
Normal Ab interaction with a currently unidentified Ag causes a conformational change in the Ag revealing a new “foreign” epitope. New IgM antibody appears as a result and reacts against pre-existing IgG, forming IgM-IgG complexes in synovial fluid. This activates complement, and then neutrophils. The neutrophils destroy cartilage with lysosomal enzymes.
Type IV hypersensitivity reactions are also known as:
Delayed-type
Which type of hypersensitivity reaction does not involve antibody?
type IV
What cells are involved in type IV hypersensitivity reactions?
- sensitized T cells
- macrophages
- NK cells
Briefly describe the mechanism of a type IV hypersensitivity reaction:
An inflammatory response induced by activated macrophages, Tc cells, and NK cells to intracellular microorganisms and/or molecular chemical irritants
Examples of type IV reactions:
- tuberculin skin test
- granulomatous reactions
- contact dermatitis
What is an epithelioid cell granuloma?
a fusion of monocytes as a result of increased IL-4 and IFN-gamma upon the persistence of microbial antigens in tissues (granulomatous reaction/type IV)
What are some drugs that treat asthma?
- Zileuton
- Montelukast
- Omalizumab/Xolair
What do Zileuton and Montelukast do?
- asthma treatment
- block luekotriene synthesis
What does Omalizumab/Xolair do?
- inhibits IgE arming of mast cells
- reduces serum IgE by 95%
In subcutaneous immunotherapy, how does increased IgG help?
1) intercepts allergen before it reaches mast cell
2) increases clearance of allergen by macrophages
3) blocks allergen epitopes from binding IgE
4) triggers inhibitory B cell receptors
5) triggers inhibitor mast cell receptors
Some examples of type II reactions:
- hemolytic disease of newborn
- autoimmune blood dyscrasias
- hyperacute graft rejection
- myasthenia gravis