Hypersensitivities - N5315 Advanced
Pathophysiology Questions and Correct
Answers
What is a hypersensitivity?
✓ ~~~ A pathological immune response to an antigen which causes tissue and
cellular damage to the host
How many types of hypersensitivities are there?
✓ ~~~ 4 types; Types 1-4
What does autoimmunity imply?
✓ ~~~ It implies an intolerance of our immune system to our own (endogenous)
antigens
What does alloimmunity imply?
✓ ~~~ Implies the formation of antibodies to foreign antigens (exogenous
antigens)
What is an Autoimmune Disease?
✓ ~~~ The pathologic consequence of autoimmunity
What often precipitates autoimmune disease?
✓ ~~~ A pathogen which triggers the immune response
What happens to the immune response that was initiated against the pathogen?
✓ ~~~ It then turns against our own antigens
What is alloimmune disease?
✓ ~~~ The pathologic consequence of alloimmunity
What it Type I hypersensitivity?
✓ ~~~ An immediate hypersensitivity response to an environmental allergen
What are most Type I hypersensitivity reactions attributed to?
✓ ~~~ Allergies to food, medication, pollen, etc.
How long do Type I hypersensitivity reactions occur after exposure to the allergen?
✓ ~~~ Minutes to hours from time of exposure
What does the Type I hypersensitivity pathogenesis begin with?
✓ ~~~ Antibody IgE
What does IgE do upon initial exposure to the allergen?
✓ ~~~ It binds with the allergen
, What does the binding of IgE to the allergen do?
✓ ~~~ It primes the stage for a reaction to occur later
What are the clinical manifestations of Type I hypersensitivities?
✓ ~~~ (dependent on route the allergen entered the body); include urticarial,
rhinitis, conjunctivitis, and asthma
What are some examples of Type I hypersensitivities?
✓ ~~~ Environmental allergies, asthma exacerbation, food allergies, drug
allergies, animal allergies, and insect venom allergies
Angioedema which causes swelling of lips, eyes, and larynx. (Anaphylaxis is most
severe reaction. Is treated with epinephrine).
Atopic Disorders include hay fever, asthma, eczema, and urticarial. They have
strong genetic disposition.
What is Type II Hypersensitivity?
✓ ~~~ (Antibody mediated or Cytotoxic Hypersensitivity); a reaction which is
mediated by antibodies directed against fixed antigens on the plasma
membranes of the cells; it is an IgG and IgM antibody mediated reaction
What does Type II Hypersensitivity pathogenesis begin with?
✓ ~~~ Binding of IgG and IgM to an antigen on the plasma membrane
What does the binding of IgG and IgM do?
✓ ~~~ It activates complement and it forms the membrane attack complex
(MAC) which causes cell lysis
What else may IgG bind to and what does this do?
✓ ~~~ IgG and C3b may also bind to the antigen and the macrophages and
trigger cell lysis through phagocytosis
What do IgG and complement attract?
✓ ~~~ Neutrophils to the tissues
What do the neutrophils do in Type II hypersensitivities?
✓ ~~~ Neutrophils perform phagocytosis and release granules which cause
tissue damage
What do NK cells do in Type II hypersensitivities?
✓ ~~~ They recognize the target cell antigen and release a toxic substance to
destroy the target cell
What do antibodies do in Type II hypersensitivities?
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