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48 Cards in this Set

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What is a type I hypersensitivity reaction?
immediate hypersensitivity
allergy
What type of antibody does Type II hypersensitivity rxn involve?
IgG
What does Type III involve?
immune complex hypersensitivity
What is Type IV hypersensitivity?
Delayed Type Hypersensitivity (DTH) = Cell-mediated Hypersensitivity
please describe a few common Type I reactions
common seasonal allergic rhinitis, allergic asthma, atopic dermatitis, acute urticaria (hives), and in the extreme situation, anaphylactic reactions.
what is a Hypersensitivity reaction
excessive immune response that causes damage
describe the term allergy
Type I Hypersensitivity - refers to certain diseases in which immune responses to environmental antigens cause tissue inflammation and organ dysfunction
what is an allergen?
an antigen that induces allergic reaction
what is atopy?
Simply stated, atopy is allergy mediated by IgE antibody. Individuals exhibiting these immediate hypersensitivity responses are called atopic.
what is the time frame and exposure necessary involved in type I reactions
occur within minutes to hours after the second exposure to an allergen

Type I reactions are initiated when allergen binds to IgE on the surface of mast cells, causing degranulation with release of bioactive substances (e.g., histamine).
where do IgE antibodies bind?
bind to high affinity FCεRI on mast cells and basophils
what should you think if you have elevated serum IgE
elevated serum levels in atopic disease and parasitic infection
does IgE activate a complement? cross the placenta? what is its structure?
-No it does not activate a complement
-it does not cross the placenta
-it is only a monomer
what additional domain does an IgE have?
has an additional H-chain domain
type I is associated with what Ab?
IgE
Type II uses what Ab?
IgG
What is another name for Type II HS rxns?
Cytotoxic
What do type III reactions use?
immune complexes
what are immune complexes (basically)
the consequence of Ab mediated immune rxns
what type of high affinity receptors do mast cells and basophils have? what do they like to bind to?
FCεRI

binds IgE
Hayfever, asthma, anaphylaxis, and atopic dermatitis are all examples of what type of hypersensitivity (HS) rxn?
Type I
What is atopy again?
A genetically determined state of hypersensitivity to common environmental allergens, mediated by IgE antibodies
what is atopy mediated by?
IgE
So if you can't see when there is tons of pollen, or if you sneeze like crazy in spring time, what kind of individual are you?
an atopic
what is Allergic Rhinitis (Hay fever)
The most common clinical expression of atopic hypersensitivity
Is atopy genetic?
yes!
if both parents are atopic, what percentage of children will be atopic?
50%
list the sequence of events for a type I rxn
allergen presented to immune system

TH2 is produced (more in atopic ppl)

Start making more IgE ab

binds to FCepsillon1 receptor on mast cell

activation occurs

granules released from mast cell (histamine and enzymes)

get hypersensitivity rxn in minutes
if atopic, what type of TH response will you have more than a non atopic person?
TH2

TH2 leads to the release of IL-4

IL4 facilitates B-cell proliferation and IgE antibody expression

thus this makes sense
What 2 cells have FCepsillon1 receptors?
basophils and mast cells
what is the most common clinical expression of atopic hypersensitivity
Allergic rhinitis
are mast cells found in the blood or tissue resident? basophil?
mast cell: tissue
basophil: blood
what preformed mediators are released by mast cell?
Histamine
Enzymes (chymase, tryptase, esterase)
what is anaphylaxis?
is an acute, generalized allergic reaction with simultaneous involvement of several organ systems --- usually cardiovascular, respiratory, cutaneous, and gastrointestinal

In other words, it is a systemic, severe form of type I hypersensitivity.
what is an Anaphylactoid reaction ?
is one in which the symptoms and signs of anaphylaxis occur in the absence of an allergen-antibody mechanism. In this case, the endogenous mediators of anaphylaxis are released in vivo through a non-immunologic mechanism
What are some of the causes of anaphylactoid reactions?
drugs, insect venom, or food
A 4-year old atopic girl (hypersensitive to various types of grass) is outdoors playing when the nextdoor neighbor starts mowing the grass.

She inhales the grass allergens and . . .
. Allergen binds to IgE on mast cells causing degranulation and release of inflammatory mediators
what do you do to treat anaphylaxis? 2
Aqueous epinephrine given I.M. or S.C. and repeated if needed.

Antihistamines for urticaria, angioedema, and GI reactions
what can be found in nasal secretions in a lab finding?
eosinophils
what is desensitization/hyposensitization
inject small amounts of allergen into patient in increasing doses over time

over time they will have a decreased response to the allergen! yay! whooppieee!
For type II HS, what are the key effector cells? 4
macrophages, neutrophils, eosinophils and NK cells
autoimmune responses are what kind of HS rxns?
Type II
Incompatible blood transfusion reactions is what type of HS rxn?
type II
Hemolytic disease of the newborn due to Rh-factor reactions is what type of HS rxn?
type II
Autoimmune hemolytic anemia, where the patient becomes sensitized to their own erythrocytes
is what type of HS rxn?
type II
Goodpasture's syndrome is what? and what type of HS rxn is it?
antibody react against glomerular basement membrane

type II
Pemphigus is what? what type of HS rxn?
antibody react to desmosome proteins in skin (get blisters)

type II
Myasthenia gravis is what type of HS rxn?
type II