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Can you distinguish between the different types of hypersensitivity reaction and their basic pathophysiologies?

Reviewed by Daniel Mercer

Hypersensitivity MCQ

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Question 1
Which type of hypersensitivity reaction is auto-immunity?
A
Type I
B
Type II
C
Type III
D
Type IV
E
This is not a hypersensitivity reaction
Question 2
Which type of hypersensitivity reaction causes rapid anaphylaxis in response to an allergen?
A
Type I
B
Type II
C
Type III
D
Type IV
E
This is not a hypersensitivity reaction
Question 2 Explanation: 
Note that a type I hypersensitivity reaction doesn't have to cause anaphylaxis; it can cause a local reaction instead. It is the immediate nature of the response which marks it out as type I.
Question 3
Which type of hypersensitivity reaction is known as a delayed hypersensitivity reaction?
A
Type I
B
Type II
C
Type III
D
Type IV
E
There is no such thing as a delayed hypersensitivity reaction
Question 3 Explanation: 
Although types II, III and IV are all slower responses, it is type IV that is known as a delayed hypersensitivity reaction. It is also known as cell-mediated.
Question 4
What substance is used as a negative control in the skin prick test?
A
Saline
B
Histamine
C
Glucose solution
D
Pure water
E
Nothing
Question 4 Explanation: 
Saline is the right answer. It is used (rather than nothing for a negative control) to prevent a phenomenon known as dermographism - see https://www.dermnetnz.org/topics/dermographism/. Pure water probably isn't used in case changes to the osmolarity of the tissue induces an inflammatory response or cell damage. Histamine is the positive control.
Question 5
True or false: an autoimmune response is triggered by the innate immune system?
A
True
B
False
Question 5 Explanation: 
Autoimmune responses are triggered by antibodies which are part of the adaptive immune system.
Question 6
Pruritus, rhinorrhoea and sneezing caused by animal dander is most likely an example of which hypersensitivity reaction?
A
Type I
B
Type II
C
Type III
D
Type IV
E
This isn't a hypersensitivity reaction
Question 6 Explanation: 
These are symptoms of hypersensitivity caused by an allergen, in this case, animal dander. These types of allergic reactions are type I reactions. Type I reactions tend to occur very soon after exposure to the allergen.
Question 7
Itching, redness and blistering around ear lobes after wearing new earrings is caused by which cells?
A
B cells
B
T cells
C
Eosinophils
D
Mast cells
E
Basophils
Question 7 Explanation: 
Contact dermatitis is an example of a type IV/cell-mediated hypersensitivity reaction
Question 8
Lupus is caused by (select two)...
A
IgA
B
IgD
C
IgE
D
IgG
E
IgM
Question 8 Explanation: 
Antibody dependent, type II immune responses are associated with autoimmunity. Handy hint: type II reactions can involve TWO different types of antibody
Question 9
T cell-mediated destruction of the intestine in coeliac disease is an example of which type of hypersensitivity reaction?
A
Type I
B
Type II
C
Type III
D
Type IV
E
This is not a hypersensitivity reaction
Question 9 Explanation: 
T cells should have been the clue that this was a type IV hypersensitivity reaction; the others are mediated by antibodies. Coeliac disease is an auto-immune condition but the destruction is mediated by T cells. According to one model (described here: https://www.the-rheumatologist.org/article/role-t-cells-celiac-disease/) B cells detect the enzyme transglutaminase (TG2) when it is bound to gluten. The B cell then presents the gluten to the T cell, activating the T cell and producing an inflammatory response that, in turn, activates epithelial cytotoxic T cells.
Question 10
Anaphylactic shock quickly following a bee sting is mediated through the actions of which cell type?
A
B cells
B
T cells
C
Mast cells
D
Eosinophils
E
Dendritic cells
Question 10 Explanation: 
Anaphylaxis is an immediate response to an allergen and as the allergen, in this case venom from a bee sting, enters the blood, the response is systemic. Immediate/type I hypersensitivity reactions are mediated by mast cells. Eosinophils can play a part in allergy, but normally the later stage of the response.
Question 11
Dry mucous membranes and changes in taste three weeks after an unidentified viral illness could be which kind of hypersensitivity reaction?
A
Type I
B
Type II
C
Type III
D
Type IV
E
This is not a hypersensitivity reaction
Question 11 Explanation: 
There are plenty of possible reasons for this (not just hypersensitivity) but conditions such as lupus and Sjogren's often target cells involved in saliva production and other secretory glands. Loss of saliva will also affect taste. Autoimmune conditions often follow infections. The theory is that infections create antibodies and the process of clonal selection (to improve recognition between antibody and antigen) can inadvertently produce antibodies that attack host cells. Autoimmune conditions are type II hypersensitivity reactions.
Question 12
A patient is poisoned by a snake and treated with serum immunoglobulin. This causes an antibody-mediated systemic inflammation and itchy rash two days later. What type of hypersensitivity reaction is this?
A
Type I
B
Type II
C
Type III
D
Type IV
E
This is not a hypersensitivity reaction
Question 12 Explanation: 
The antibodies and the timing are the key parts to this question. Because the response isn't immediately after exposure to the immunoglobulin it isn't a type I reaction, and while proteins could trigger an auto-immune reaction (type II) it's faster than you'd probably expect. Type IV reactions are T cell-mediated, not antibody-mediated which leaves us with a type III reaction. A serum is the term given to a protein-rich liquid. In case you're interested, in a type III reaction, antigens are detected by the body and form immune complexes with antibodies. When there are insufficient antibodies to trigger an immune response the antigen-antibody complexes travel through the blood and get deposited in blood vessel walls and other tissues where they will more-slowly trigger inflammatory responses.
Question 13
The raised, red spot at the site of a tuberculin skin test is a result of which type of hypersensitivity reaction?
A
Type I
B
Type II
C
Type III
D
Type IV
E
This is not a hypersensitivity reaction
Question 13 Explanation: 
The tuberculin skin test is a delayed/cell-mediated hypersensitivity reaction that is caused by T cells. You may also hear this test referred to as the Mantoux test. Older patients may have had the less-reliable Heaf test in the past, which featured multiple punctures made in a small circle. For further details, see: https://labtestsonline.org.uk/tests/tb-skin-test
Question 14
Vasodilation following a type I hypersensitivity reaction is principally caused by which molecule?
A
Histamine
B
Leukotriene
C
Bradykinin
D
IL-4
E
Tryptase
Question 14 Explanation: 
All of the above (except IL-4) are released from mast cells; histamine is the one mainly responsible for vasodilation. IL-4 is responsible for class-switching, triggering B cells to produce IgE antibodies.
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