Hypersensitivity Flashcards
With reference to immunology, what is hypersensitivity?
It’s a term used to describe immune systems that are inappropriate, because:
- they’re of too great a magnitude
- they’re responding to something we don’t need the system to respond to
- they’re happening at a location in the body where we shouldn’t be getting that kind of immune response
OR
exaggerated/inappropriate immune response leading to pathology
There are 4 hypersensitivity types. Describe each one.
- IgE mediated mast cell degranulation
- Cytotoxic antibodies against cell surface antigens
- Immune complex mediated hypersensitivity
- Delayed type hypersensitivity mediated by T cells
1 to 3 mediated by antibody. 4 mediated by T cells.
What is the name of the high affinity IgE receptor on the surface of mast cells?
FcepsilonR1
What is meant by anaphylaxis?
The term is used to describe a severe systemic hypersensitivity to an allergen in an injection, sting or by epithelial exposure. It involves rapid vasodilation leading to a substantial drop in blood pressure. There is constriction of airways, edema and anaphylactic shock that is often fatal
What can reverse the bronchoconstriction and vasodilation to rescue the patient?
Immediate administration of epinephrine
What are the mediators that mast cells produce that contribute to the inflammatory process?
Group 1: stored in granules
- histamine
- heparin
- eosinophil chemotactic factor
Group 2: newly synthesized from ararchidonic acid
- prostagalndin:D2, E2, F2alpha
- leukotriene B4
- leukotriene: C4, D4, E4
Give a description of phases of Type 1 hypersensitivity response.
Immediate response- IgE mediated
Late phase reaction- CD4 helper T cell, monocyte, and eosinophil mediated
If a patient was unable to synthesize mediators from arachidonic acid during type 1 hypersensitivity reaction, what characteristic effect would be absent?
Neutrophil chemotaxis
Aspirin inhibits the cyclooxygenase pathway by irreversibly inhibiting the rate limiting enzymes COX1 and COX2. Which mediator is most affected?
Prostaglandins
Genetic polymorphism in which cytokine is associated with an increased hypersensitivity response?
IL-2 and IL-33
How can atopic allergy be diagnosed?
Using the skin prick test: small amount of suspected allergen are injected under the skin.
There’s a release of inflammatory mediators from any mast cells that are pre sensitized with IgE antibody against suspected allergen. Leads to vasodilation and edema causing characteristic wheal and flare response.
What does RAST stand for?
Radioallergosorbent
What are therapeutic options for allergy?
- removal or avoidance of allergic triggers
- H1 blockers
- mast cell stabilizers
- anti inflammatory corticosteroids and leukotriene inhibitors
- immunotherapy
Which other monoclonal antibody is specific for IgE?
Omalizumab
What is albuterol?
Beta-adrenergic receptor
What does the allergy skin prick test rely on?
Mast cells that have been sensitized to the allergen in the past
What type of antibodies are present in Type A blood group?
A antigens are present therefore Anti-B antibodies are present
What type of antibodies are present in Type B blood group?
B antigens are present therefore Anti-A antibodies are present
What type of antibodies are present in Type AB blood group?
There are A and B antigens present therefore no antibody is produced against either
What type of antibodies are present in Type O blood group?
There are no antigens present therefore Anti-A and Anti-B antibodies are produced
What is hemolytic disease of the fetus and newborn (Rhesus D incompatibility)
A mother is rhesus D negative, her partner is Rhesus D positive therefore the baby is Rhesus D positive. Not a problem during first pregnancy. During labor fetal red cells leak into mother, mother makes an antibody response. A problem arises in second pregnancy as the maternal D antibodies can cross the placenta. They will attack fetal red cells. Rare condition due to Rhesus D prophylaxis.
What occurs during the hypersensitivity reaction of Graves’ disease?
Autoantibodies against the TSH receptor lead to overproduction of thyroid hormone
Why will a Rhesus D negative mother have antibodies against Rhesus D only after her first pregnancy?
Exposure to Rhesus D during labor is required for IgG anti-rhesus antibodies to develop
The ‘giant cells’ that can be present in a granuloma are derived from?
Macrophages
A key aspect of type 4 hypersensitivity is the activation of?
Cytotoxic T cells by cytokines
A structure composed of a large amount of activated macrophages surrounded by fibroblasts is?
Granuloma
