Hypersensitivity

Question 1

With reference to immunology, what is hypersensitivity?

Answer 1

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

Question 2

There are 4 hypersensitivity types. Describe each one.

Answer 2

1. IgE mediated mast cell degranulation
2. Cytotoxic antibodies against cell surface antigens
3. Immune complex mediated hypersensitivity
4. Delayed type hypersensitivity mediated by T cells

1 to 3 mediated by antibody. 4 mediated by T cells.

Question 3

What is the name of the high affinity IgE receptor on the surface of mast cells?

Answer 3

FcepsilonR1

Question 4

What is meant by anaphylaxis?

Answer 4

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

Question 5

What can reverse the bronchoconstriction and vasodilation to rescue the patient?

Answer 5

Immediate administration of epinephrine

Question 6

What are the mediators that mast cells produce that contribute to the inflammatory process?

Answer 6

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

Question 7

Give a description of phases of Type 1 hypersensitivity response.

Answer 7

Immediate response- IgE mediated

Late phase reaction- CD4 helper T cell, monocyte, and eosinophil mediated

Question 8

If a patient was unable to synthesize mediators from arachidonic acid during type 1 hypersensitivity reaction, what characteristic effect would be absent?

Answer 8

Neutrophil chemotaxis

Question 9

Aspirin inhibits the cyclooxygenase pathway by irreversibly inhibiting the rate limiting enzymes COX1 and COX2. Which mediator is most affected?

Answer 9

Prostaglandins

Question 10

Genetic polymorphism in which cytokine is associated with an increased hypersensitivity response?

Answer 10

IL-2 and IL-33

Question 11

How can atopic allergy be diagnosed?

Answer 11

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.

Question 12

What does RAST stand for?

Answer 12

Radioallergosorbent

Question 13

What are therapeutic options for allergy?

Answer 13

• removal or avoidance of allergic triggers
• H1 blockers
• mast cell stabilizers
• anti inflammatory corticosteroids and leukotriene inhibitors
• immunotherapy

Question 14

Which other monoclonal antibody is specific for IgE?

Answer 14

Omalizumab

Question 15

What is albuterol?

Answer 15

Beta-adrenergic receptor

Question 16

What does the allergy skin prick test rely on?

Answer 16

Mast cells that have been sensitized to the allergen in the past

Question 17

What type of antibodies are present in Type A blood group?

Answer 17

A antigens are present therefore Anti-B antibodies are present

Question 18

What type of antibodies are present in Type B blood group?

Answer 18

B antigens are present therefore Anti-A antibodies are present

Question 19

What type of antibodies are present in Type AB blood group?

Answer 19

There are A and B antigens present therefore no antibody is produced against either

Question 20

What type of antibodies are present in Type O blood group?

Answer 20

There are no antigens present therefore Anti-A and Anti-B antibodies are produced

Question 21

What is hemolytic disease of the fetus and newborn (Rhesus D incompatibility)

Answer 21

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.

Question 22

What occurs during the hypersensitivity reaction of Graves’ disease?

Answer 22

Autoantibodies against the TSH receptor lead to overproduction of thyroid hormone

Question 23

Why will a Rhesus D negative mother have antibodies against Rhesus D only after her first pregnancy?

Answer 23

Exposure to Rhesus D during labor is required for IgG anti-rhesus antibodies to develop

Question 24

The ‘giant cells’ that can be present in a granuloma are derived from?

Answer 24

Macrophages

Question 25

A key aspect of type 4 hypersensitivity is the activation of?

Answer 25

Cytotoxic T cells by cytokines

Question 26

A structure composed of a large amount of activated macrophages surrounded by fibroblasts is?

Answer 26

Granuloma