title:
<h2 align=center>The Lymphoid System & Hypersensitivity Reactions</h2>
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Practice your knowledge of the concepts raised in the lectures and readings dealing with the immune response and hypersensitivity reactions.<br>
In the multiple choice answers click on whichever answer you feel is the most appropriate. When finished submit your quiz for marking and your result will be returned to you within a few minutes.<br>


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<hr size=2>
header:
<h3 align=center>Immune System</h3>

footer:

<address>Please e-mail feedback to <a href="mailto:bertha.garcia@lhsc.on.ca">The Meds I Pathology Course Coordinator</a>
</address>

delivery:
simultaneous


question:
A 40-year-old-male developed fever, chills, dyspnea and facial flushing immediately after a blood transfusion. On examination he was tachycardic and hypotensive. <br>
Which of the following mechanisms might have mediated this reaction? 
ans: 
Activation of the complement system by antigen-antibody complex.
fbk:
Incorrect. This mechanism is involved in the Type III hypersensitivity reaction, in which there is deposition of immune complex in the blood vessels and along the glomerular basement membranes. These complexes then activate the complement system with subsequent tissue destruction. Best examples are SLE and Glomerulonephritis.
ans:
Antibody-dependent cytotoxicity by NK cells.
fbk:
Incorrect. This involves antibody-coated target cells, which are then destroyed by NK cells. Occurs in Type II hypersensitivity reaction. Examples are parasitic infections.
ans:
Antigen-mediated degranulation of mast cells.
fbk:
Incorrect. This is the mechanism of tissue injury in Type I hypersensitivity, mediated by Th2 T-lymphocytes. Exposure to antigen causes B cells to produce IgE which then binds to mast cells causing degranulation. Examples are asthma, food allergies and penicillin allergy.
ans:
T cell mediated cytotoxicity.
fbk:
Incorrect. This is Type IV hypersensitivity. Example is transplant rejection.
ans:
Complement-mediated generation of C5-9 membrane attack complex.
fbk:
Correct. This patient had a transfusion reaction resulting from IgM or IgG-mediated complement activation. This results in generation of the membrane attack complex which then lyses the recipient RBCs. It is an example of complement-mediated Type II hypersensitivity reaction.
correct_answer:
5
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question:
An 11-year-old boy was brought to the ER with a history of generalized edema and oliguria. He also complained of passing coke-colored urine for the past few days. <br>
Lab investigations showed low serum complement levels with high anti-streptolysin (ASO) titers. A renal biopsy was then performed and immunoflouresence studies showed IgG and C3 deposited along the glomerular basement membranes.<br>
What is the most likely pathogenesis of his disease?
ans:
Antibody mediated basement membrane injury.
fbk:
Incorrect. By this mechanism, circulating antibodies bind to fixed antigens in connective tissue and lead to complement activation. Seen in Goodpasture syndrome and pemphigoid. 
ans:
Immune complex mediated complement activation.
fbk:
Correct. This patient has Post-infectious (streptococcal) glomerulonephritis. The mechanism in this type of injury is related to the formation of IgG, IgM or IgA against a circulating antigen. These antibody-antigen complexes formed in the circulation then deposit in different tissues like renal glomerulus, skin venules, lungs and synovium. There they activate the complement system leading to release of tissue-damaging mediators. This is an example of Type III hypersensitivity reaction.
ans:
T-cell mediated cytotoxicity.
fbk:
Incorrect. This is the mechanism involved mostly in virus-infected cells or tumor neoantigens. It is a Type IV hypersensitivity reaction. Not the case in this patient.
ans:
Antibody mediated tissue function alterations.
fbk:
Incorrect. This is a Type II hypersensitivity reaction. Antibodies are directed against cell receptors which lead to impairment of function and not tissue destruction. Example includes Grave's disease.
ans:
Complement mediated reaction.
fbk:
Incorrect. This occurs as a consequence of Type II hypersensitivity reaction. examples are hemolytic anemias and transfusion reaction.
correct_answer:
2

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question:
The above patient most likely had a past history of which of the following disease?
ans:
Streptococcal skin infection.
fbk:
Correct. History of streptococcal skin infection like Impetigo or streptococcal pharyngitis can be elicited in post-infectious glomerulonephritis. Note high ASO titres.
ans:
Viral infection.
fbk:
Incorrect. There is no suggestive history in this patient.
ans:
Tuberculous infection.
fbk:
Incorrect. It does not lead to glomerulonephritis, which is the disease in this patient.
ans:
Allergies.
fbk:
Incorrect. They are not related to renal disease as such.
ans:
Immunosuppression.
fbk:
Incorrect. This patient does not have any history of being on immunosuppressive therapy or symptoms related to immunosuppression.
correct_answer:
1

<p>

question:
A 31-year-old-male presented with nasal pruritis, rhinitis, congestion and paroxysms of sneezing. He also complained of chest tightness and dyspnea. On examination he had audible wheezes and an erythematous rash over his arms. A skin test was positive for a specific IgE-antibody.<br>
 This patient has most likely which type of underlying hypersensitivity reaction?
ans:
Type I.
fbk:
Correct. The symptoms in this patient suggest an event of allergic rhinitis with systemic anaphylaxis. This is an example of Type I hypersensitivity reaction where IgE produced from the B cells binds to mast cells which release certain mediators to elicit an anaphylactic reaction. 
ans:
Type II.
fbk:
Incorrect. It is not the case in this patient.
ans:
Type III.
fbk:
Incorrect. Symptoms are different in diseases related to this type of reaction.
ans:
Type IV.
fbk:
Incorrect. Not present in this patient.
correct_answer:
1

<p>

question:
Which of the following mediators is most likely involved in the causation of the symptoms in the above case?
ans:
IL 1.
fbk:
Incorrect, produces fever and inflammation.
ans:
C5 a.
fbk:
Incorrect, it is a chemotactic factor.
ans:
Histamine.
fbk:
Correct. This patient is suffering from allergic rhinitis with systemic anaphylaxis. Histamine is a potent mediator in this type of hypersensitivity reaction.
ans:
Bradykinin.
fbk:
Incorrect. It is involved in pain and vascular permeability.
ans:
Thromboxane A2.
fbk:
Incorrect. It is a product of the arachidonic acid pathway. It induces vasoconstriction and enhances platelet aggregation.
correct_answer:
3

<p>

question:
All of the following may induce the above reaction, except;
ans:
Poison ivy.
fbk:
Correct. Induces Type IV delayed hypersensitivity.
ans:
Bee sting.
fbk:
Incorrect. Produces Type I hypersensitivity reaction as above.
ans:
Penicillin.
fbk:
Incorrect. Produces Type I hypersensitivity reaction as above.
ans:
Dust.
fbk:
Incorrect. Produces Type I hypersensitivity reaction as above.
ans:
Lobster.
fbk:
Incorrect. Produces Type I hypersensitivity reaction as above.
correct_answer:
1
<p>


question:
An HIV patient was given a tuberculin test. Although he had a strong history of exposure to Mycobacterium tuberculous infection and had developed signs and symptoms of the disease, he reacted less vigorously to the test. Deficiency of which of the following has most likely caused the lack of response?
ans:
CD4 cells.
fbk:
Correct. The tuberculin test induces a delayed Type IV hypersensitivity reaction. It primarily involves lymphocytes and mononuclear phagocytes. The foreign antigen or protein is engulfed by macrophages bearing class II HLA-D molecules. They are recognized by CD4 lymphocytes which then become activated. The human immunoeficiency Virus (HIV) attacks the CD4 lymphocytes with resultant decrease in their numbers, therefore these patients may not respond to the test as vigorously as normal individuals do.
ans:
B cells.
fbk:
Incorrect. Are not involved in this type of reaction.
ans:
Platelets.
fbk:
Incorrect. Are not involved in this type of reaction.
ans:
Complement proteins.
fbk:
Incorrect. Are not involved in this type of reaction.
ans:
Immunoglobulins.
fbk:
Incorrect. Not a major target for Human Immunodeficiency Virus. Are not invoved in this type of reaction.
correct_answer:
1

<p>

question:
Reaction to tuberculin test is an example of which of the following mechanisms?
ans:
Activation of CD4 T lymphocytes with release of lymphokines.
fbk:
Correct. It occurs in delayed Type IV hypersensitivity reaction. 
ans:
CD8 T lymphocytes and MHC I induced cell injury.
fbk:
Incorrect. It occurs in T cell mediated cytotoxicity of virus infected target cells and tumor neoantigens. Also play an important role in graft or transplant rejection. 
ans:
Direct injury to the target cells by NK cells.
fbk:
Incorrect. Results in binding of NK cells to the target cells through membrane receptors. They deliver molecular signals to cause cell lysis. 
ans:
T cell mediated mast cell activation.
fbk:
Incorrect. It occurs in type I hypersensitivity reaction. Not evident in this patient.
ans:
Antibody-coated cell destruction by NK cells.
fbk:
Incorrect. It occurs as a result of Type II hypersensitivity reaction. May occur in some autoimmune diseases and killing of large parasites.
correct_answer:
1

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