Hypersensitivity 1 Flashcards
Hypersensitivity disorders are _
Diseases caused by the immune system
The 3 main ways that the immune system can cause tissue damage are by _
Rxn against microbes
Rxn against environment
Rxn against self
When immune rxns are mounted against microbes, there are 3 ways the rxn can damage the host. They are _
excessive / unusually persistent response
antibodies deposit in tissues
antibodies cross react
An example of an unusually excessive / persistent disease is _
Granuloma formation in tissues
An example of a case where antibodies deposit in tissues is _
post-streptococcal glomerulonephritis
An example of a case where antibodies cross react with normal tissues is _
Rheumatic fever
About what percentage of the population react to environmental substances?
20%
Auto-immune disease arises because _
The nomal self tolerance mechanisms fail
What percentage of the population suffers from autoimmune disease? What is the age group?
5%
20 - 40 yrs old
The mechanisms of autoimmunity are different from the mechanisms of host defense against pathogens. T or F
False. The same mechanisms
Type 1 hypersensitivity is also known as _. It is mediated by what type of antibody?
Immediate
IgE
What is the mechanism of type 1 hypersensitivity?
Mast cells and their mediators. Think allergic
What are the antibody mediators of type 2 hypersensitivity?
IgM and IgG against self tissues
What is the mechanism of type 2 hypersensitivity?
Opsonization / phagocytosis, complement, recruitment of leukocytes
What are the antibodies that mediate type 3 hypersensitivity?
IgM and IgG
What is the mechanism of type 3 hypersensitivity?
Immune complexes deposit in tissues. Complement and Fc recruitment of leukocytes
What are the immune mediators of type 4 hypersensitivity?
CD4 - cytokine mediated inflammation
CD8 - Cell mediated autolysis
What is the mechanism if type 4 hypersensitivity?
Leukocyte activation and recruitment, cytokine inflammation, cell killing
What 2 types of hypersensitivity are mediated by antibodies?
Types 2 and 3
What type of hypersensitivity doesn’t depend on leukocyte recruitment?
Type 1
Types 2 and 3 hypersensitivity are both antibody mediated. What is the difference?
In type 2, the antibody is directed against the tissue. In type 3, the antibody accumulated in the area of the tissue
When examined by immuno-fluorescence, what would you expect to see when comparing antibody deposition between type 2 and 3 reactions?
Deposition is smooth in type 2 rxns
Deposition is coarse in type 3 rxns
An example of a type 2 rxn where antibodies directed against RBCs destroy the cells is _.
Autolytic hemolytic anemia
Antibodies against CD20 would be expected to _
Destroy B cells
What is the Coomb’s test?
It is a test to detect the presence of anti-RBC antibodies
Would you expect a type 2 rxn to yield systemic or non-systemic disease?
Non-systemic, tissue targeted / specific
What are the 3 mechanisms by which a type 2 rxn can cause tissue injury?
Opsonization
Damage to tissue proteins
Antibody deposition in tissues
3 examples where antibodies bind to cells to mediate autoimmune rxns (phagocytosis) are _. What type of hypersensitivity is this?
Autoimmune hemolytic anemia
Autoimmune thrombocytopenic purpura
Hemolysis following blood transfusion
Type 2
3 examples where antibodies bind to tissues to mediate autoimmune reactions are _. What type of reaction is this?
Good pastures syndrome
Glomerulonephritis
Acute rheumatic fever
Type 2
What are myesthenia gravis and graves disease? What type of hypersensitivity is this?
Myesthenia - The antibodies block receptor function
Graves - Antibody stimulates the thyroid
Type 2 hypersensitivities
What is the manifestation of autoimmune thrombocytopenic purpura?
Bleeding
What is Goodpasture’s syndrome?
Abs target NC1 in basement membrane of glomerulus and lungs. Leads to nephritis, lung hemmorhage
What is pemphigus vulgaris?
Antibodies against intercellular desmoglein in epidermis. Leads to skin vesicles (blisters)
Glomerulo-nephritis is not the same as post-streptococcal glomerulonephritis. In post-streptococcal, _
Group A strep antibodies and their antigen deposit in glomeruli, leading to inflammation
Type 3 rxn are more likely to be [systemic/non-systemic]
Systemic, the complex can deposit anywhere
The mechanism of damage in type 3 rxns is _
Immune complexes activate Fc-mediated inflammation and complement to damage blood vessels and surrounding tissues
Areas susceptible to type 3 rxn are areas where plasma ultra-filtration occur. These are _ (3)
Kidney
Joints
Vasculature
Are larger or smaller complexes more likely to form deposits in vessel walls?
Smaller. Larger complexes attract complement, cleared by phagocytosis
What is Arthus reaction?
This is where a previously immunized animal is adminstered a local bolus of antigen (subQ). This results in a localized inflammation mediated by antibody, causing local cutaneous vasculitis and necrosis
What is serum sickness?
It is observed when people are innoculated with horse antibody. Occurs 7-10 days later (igG response time). Fever, chills, rash, arthritis, glomerulonephritis
Systemic Lupus Erythematosus (SLE) is the prototype immune complex disease. Antibodies are targeted towards _
DNA
Nucleoproteins
Others
What are the 2 major means by which Type 4 rxns cause tissue damage?
Triggering inflammation
Direct tissue killing
CD4 cells can recruit macrophages and neutrophils. What are the subtypes responsible and what is the major cytokine?
Macrophages - Th1 - IFN-gamma
Neutrophils - Th17 - IL-17
The classical T-cell mediated inflammation is _
Delayed type hypersensitivity
What is the timeline for delayed type hypersensitivity? What are 2 examples provided?
24-48 hrs
PPD test, contact dermatitis
In DTH, what is occuring at 4 hrs? 12 hrs? When is peak induration occuring?
4 hrs - Neutrophils around post-cap. venules
12 hrs - T cells and monocytes around venules
Peak induration - 24-48 hrs
Delayed type hypersensitivity requires prior exposure to antigen. True or false
True
A example of chronic type DTH is _. What is a characteristic finding?
Tuberculosis
Granulomas (nodules of inflammatory cells), Fused macrophages to form multinucleate giant cells
Difficulty breathing following prolonged TB infection is due to _
Fibrotic tissue from inflammation, not the microbe itself
The major CD4 subtype involved in granuloma formation and its cytokine is _
TH1, IFN-gamma
What do RA, MS, Type 1 diabetes and IBS have in common?
All type 4 hypersensitivity reactions.
Poison Ivy dermatitis is an example of _. The allergen here is Urushiol
Type 4
Treatment of poison ivy can be done with _
Corticosteroids (topical or systemic, depending on severity)
What is the patch test?
Allergy panel test
