Immuno: Hypersensitivity Flashcards
Hypersensitivity:
-Immune and inflammatory responses that are an over reaction of the immune system
-caused by allergens
Allergic reactions =
Subtype of hypersensitivity
Only 20% of population reacts to allergens, what causes those two percent to be allergic:
-genetic predisposition
-hygiene hypothesis
Genetic predisposition to allergens:
IL-4 receptor modification causes a lot of class switching leading to an abnormal level of IgE being produced
Hygiene hypothesis for 20% of population reacting to allergens:
Less burden of helminths/worms -> high levels of IgE body
Type 1 hypersensitivity is also called:
Immediate hypersensitivity
Type 2 hypersensitivity is also called:
Antibody-dependent hypersensitivity
Type 3 hypersensitivity is also called:
Antibody antigen complex hypersensitivity
Type 4 hypersensitivity is also called:
Cell-mediated or delayed hypersensitivity
Type 1-3 hypersensitivity is ____ mediated
Ab
Type 4 hypersensitivity is _____ mediated
T-cell
Type I hypersensitivity is an allergic reaction provoked by..
Reexposure to a specific antigen, where exposure may be ingestion, inhalation injection or direct contact
Type I hypersensitivity causes an inflammatory responses leading to an immediate reaction within…
Seconds to minutes
Type I hypersensitivity reactions can be either _______ or __________ with symptoms ranging from mild ____________ to sudden death from __________________
Local, systemic, irritation, anaphylactic shock
First exposure to allergen in type I hypersensitivity:
IgE is made by activated B cells (via IL-4) in response to allergen
What is the key cytokine for production or “switching” to IgE?
IL-4
After the first exposure in type I hypersensitivity there is a priming stage. What occurs?
Binding of IgE to Fc elipson receptor 1 on the surface of mast cells and basophils
Second exposure to allergen in type I hypersensitivity:
Antigen cross-links IgE on the surface of mast cells, causing the release of the granule’s contents
In type I hypersensitivity, after the second exposure, degranulation occurs which causes the release of ____________ and other inflammatory mediators such as __________ and ____
Histamine, proteases and TNF
Early symptoms of a type I hypersensitivity reaction:
-degranulation releasing histamine
-synthesis/release of leukotrienes and prostaglandins
-edema, redness, itching
Type II hypersensitivity is also known as _____________ hypersensitivity
Cytotoxic
What antibodies are produced by the immune system to bind antigens on the patients own cell surfaces in type II hypersensitivity?
IgG and IgM
Reaction time for type II hypersensitivity
Minutes to hours
Diseases related to type II hypersensitivity all have a common theme:
Antibodies are directed against tissues or cells of our own body
Examples of diseases in type II hypersensitivity:
-rheumatic fever
-autoimmune hemolytic anemia
-exposure to wrong blood type
-myasthenia gravis
Type II hypersensitivity is where soluble immune complexes, such as _____ and ______ form in the ______ and are deposited in various _________
IgG and IgM, blood, tissues
Type III hypersensitivity can trigger an immune response leading to the classical pathway of _________________ which takes ____________ to develop
Complement activation, hours to days
Example of generalized type III hypersensitivity:
Serum sickness where immune complexes in plasma lead to systemic disease
(Examples are rabies or tetanus anti-toxin)
Example of a localized reaction in type III hypersensitivity:
Arthus reaction which is often reported with skin injections
Hypersensitivity pneumonitis:
-A type III hypersensitivity reaction often called farmers lung. - a hypersensitivity reaction to an environmental antigen
Type IV hypersensitivity is ______________ and has no _____________ involved
Cell mediated, no antibodies
In type IV hypersensitivity, what initiates the response to the antigen since there are no antibodies involved?
Memory T cells
Tuberculosis test (PDD test) involves type IV hypersensitivity. What are the steps?
-tuberculin protein is injected into skin
-previously exposed person has memory T cells
-CD4 T cells recognize protein on APC MHCII
-TH1 response
-IFN gamma activates macrophages
-IL-12 from macrophages stimulates TH1 cells
-results in redness that begins 24-72 hours later
Contact dermatitis is what type of hypersensitivity?
Type IV
Response time of type IV hypersensitivity in contact dermatitis
12-48 hours (much longer than type I)
Phylrctenulosis is what type of hypersensitivity?
Type IV
Toxic mediators in type I hypersensitivity utilize _________ and ___________ that leads to:
Histamine, heparin
-vascular permeability -> edema (wheal)
-vasodilation in cutaneous blood -> reddening skin
-smooth muscle contraction (bronchospasam)
Toxic mediators are released from ___________
Granules
Types of lipid mediators in type I hypersensitivity:
-prostaglandins and leukotrienes
-platelet-activating factor
Prostaglandins in lipid mediation leads to:
Enhanced vasodilation and attraction of neutrophils
Leukotrienes in lipid mediation leads to:
-Induced smooth muscle contraction and mucus secretion
-increased vascular permeability
Lipid mediators are synthesized after ___________
Activation
Cytokines in type I hypersensitivity are involved in the ____________ reaction
Late-phase reaction
What are significant sources of cytokines?
Mast cells
-TNF
-IL-4, IL-13
-IL-3, IL-5, GM-CSF (granulocyte macrophage costimulatory factor)
TNF cytokine in type I hypersensitivity promotes ____________
Inflammation
IL-4 and IL-13 in hypersensitivity type I stimulate/amplify the _____ response
TH2
IL-3, IL-5, and GM-CSF promote…
Eosinophils maturation, differentiation, and survival
Cytokines in type I hypersensitivity are synthesized after ____________
Activation
Desensitization is a…
Gradual administration of increasing amounts of allergen causing the response to change from IgE to IgG (IgG blocks mediator response)
Another name for desensitization
Modified TH2 responses
Hemolytic disease of the newborn
If an Rh - mom is pregnant w an Rh + fetus, the fetal-maternal bleed releases the Rh+ into moms blood causing mom to produce anti-Rh IgG, which can cross placenta
Phlyctenular keratoconjctivitis (PKC) :
Modular inflammation of the cornea or conj due to type IV hypersensitivity reaction to antigens of bacterial origin
PKC is secondary to ________ due to staphylococcus aureus
Blepharitis
Cells isolated in PKC:
-CD4
-CD8
-langerhans cells
Wheal-and-flare inflammatory reaction is an example of…
An immediate type I allergic reaction
The antigens that provoke hypersensitivity reactions are referred to as _______
Allergens
Subsequent pregnancy with Rh+ fetus puts baby at risk with which antibody?
IgG
Can a first time exposure elicit a true allergic reaction?
NO
Purified protein derivatives of mycobacterium tuberculosis would elicit which type of hypersensitivity reaction in BCG vaccinated population?
Type IV hypersensitivity
