Microbiology 532Immunology Examination
Microbiology 532
Immunology Examination KEY
October 16, 1998
All questions have equal point value.
SCENARIO I
You are the dental public health official in the new country of Edentia and it is your responsibility to improve the state of dental health in your country. You decide to immunize the entire population with a new caries vaccine that has recently been developed against an antigen of Strep. causealotofcaries, the etiologic agent of caries in your country. Three days after immunization, you find that the etiologic agent has been eliminated only in women who are Rh negative and have given birth to Rh positive children. You now have to figure out the reason for this mystery.
Multiple Choice (choose the best answer)
D 1.You develop an agglutination assay using a purified antigen from Strep. causealotofcaries. The assay detects no antibodies to that antigen. What do you suspect?
a.The antigen may be similar to the A blood group antigen.
b.The antigen may be similar to the B blood group antigen.
c.The antigen may be similar to the O blood group antigen.
d.The antibodies are probably of the IgG class.
e.None of the above.
A 2.You develop a precipitation assay using purified antigen to detect antibodies to Strep. causealotofcaries and it tells you that the protected subjects are producing antibodies. What do you suspect?
a.The antibody providing protection is of the IgG class.
b.The antibody providing protection is of the IgA class.
c.The antibody providing protection is of the IgE class.
d.The antibody providing protection is of the IgM class.
e.None of the above.
C 3.Based on the results in questions 1 and 2, you develop an ELISA assay using an extract of the entire microorganism and a second antibody that ensures that it detects only antibodies of the IgG class. How do you ensure that the assay detects only IgG antibodies?
a.Use a “second antibody” that only detects µ chains.
b.Use a “second antibody” that only detects kappa and lambda chains.
c.Use a “second antibody” that only detects gamma chains.
d.Use a “second antibody” that only detects the entire IgG molecule.
e.None of the above.
A 4.Your ELISA assay indicates that all of the subjects make antibodies to the whole cell extract. You are beginning to question whether immunity is a factor at all in protection against this microbe. You are convinced that you might need to look at immunity directed to specific epitopes of this microorganism. What made you think of this?
a.A specific epitope important in the microorganism’s adherence to host cells may not be recognized by all subjects’ immune systems.
b.In addition to antigen, other substances called epitopes may be recognized in certain individuals.
c.Antigenic determinants occur in all antigens, but epitopes are present only in carbohydrate antigens.
d.Only substances that cross-react with blood group substances are epitopes.
e.None of the above.
A 5.Your epitope-specific ELISA assay indicates that there is one epitope that is not recognized in the unprotected patients. Since this epitope is only recognized by the Rh negative women who have given birth to Rh positive children, what do you suspect about the protective antibodies?
a.The protective antibodies are directed against the Rh antigen.
b.The protective antibodies are directed against an epitope which is probably part of the type A antigen.
c.The epitope is probably associated with the H substance.
d.The epitope is probably associated with the B antigen.
e.None of the above.
D 6.Why do you think the Rh positive subjects don’t make a protective antibody against the vaccine?
a.There is a response but we can’t detect it.
b.Rh positive individuals are too hyper to mount a good immune response.
c.The IgM and IgG antibodies that are produced neutralize each other.
d.Because the important component is a “self” epitope, they are unable to recognize it immunologically.
e.None of the above.
B 7.In the protected subjects, there is no evidence of colonization of this microbe. How do you think that protective antibody is working?
a.The antibody activates innate host defense mechanisms.
b.The antibody probably blocks the epitope that is involved in the binding of the microorganism to the host.
c.The antibody neutralizes complement components that interfere with bacterial adherence.
d.All of the above
e.None of the above.
A 8.How would you reformulate the vaccine in order to protect the Rh positive subjects?
a.I would try to identify other epitopes important in microbial virulence that are recognized immunologically by all subjects regardless of blood type.
b.I would heat the vaccine to 56°C for 30 minutes to destroy tissue-fixing ability.
c.I would digest the vaccine with protease to remove all cross-reactive proteins.
d.I would just give up and accept the fact that they won’t be protected (you can’t pick this because you are dedicated to the protection of all).
e.none of the above.
D 9.Ten years following the first series of immunizations, your patients still appear to be resistant to caries. How do you explain this?
a.Someone has been secretly re-immunizing these folks every year (don’t pick this answer).
b.All of their teeth fell out and it is not possible to get any more caries (don’t pick this answer).
c.The initial series of immunizations induced immune paralysis.
d.Immunologic memory is maintaining protection.
e.None of the above.
D 10.Twenty years later you discover that the previously immunized subjects were also protected against several other completely unrelated microorganisms. How do you explain this?
a.The adjuvant induced a heightened innate protective response.
b.The immunizations resulted in autoreactive antibodies causing a protective type V hypersensitivity.
c.The immunizations resulted in passive immunity to these other microorganisms.
d.The unrelated microorganisms apparently share common epitopes and the antibodies are cross-reactive.
e.None of the above.
SCENARIO II
You have been asked to consult in a clinical diagnostic laboratory. The lab is trying to determine why its new antibody assay system is not accurately detecting protective antibodies in the sera of persons recently exposed to Bonga-Bonga fever virus. This is very frustrating to the laboratory since they had no problems until the FDA mandated that they discontinue using an agglutination assay. The new assay is a very sensitive ELISA. It has been telling them that everyone is making antibodies, regardless of exposure (or lack of exposure) to the Bonga-Bonga fever virus. The ELISA uses a “second antibody” made by immunizing rabbits with purified human IgG. It is imperative that we identify the truly unprotected individuals because we don’t have enough antiviral compounds to effectively treat all of the Bonga-Bonga fever-exposed subjects.
True/False (Please use “a” for true and “b” for false on your answer sheet)
F 11.Since agglutination assays favor the detection of IgG antibodies, the protective antibodies are probably of the IgG class.
F 12.The ELISA detects the activation of the complement system and is dependent on preliminary precipitation or agglutination.
F 13.The “second antibody” in the ELISA is probably contributing to the problem since it reacts with all immunoglobulin heavy chains.
F 14.The “second antibody” is specific for IgM.
F 15.A precipitation assay might work better than the ELISA as a substitute for the agglutination assay because precipitation requires cross-linking of particulate antigen and is efficient with IgM antibodies.
Non-SCENARIO Questions
T 16.The destructive activity of the complement system is limited to the location of its activation due to the short half-lives of the components and the presence of competitive inhibitors.
T 17.Antigen receptors on B cells have the same specificity as the antibody product that those cells will make once they have matured and differentiated to plasma cells.
F 18.The major histocompatability complex-encoded proteins on the surface of antigen-presenting cells ensure proper presentation of antigenic peptides to the B-cell.
T 19.In order for cells to communicate with one another, one cell must have a receptor for the signal/soluble factor that the other cell is sending.
T 20.Innate host defense factors generally protect the host prior to the induction of the adaptive defenses.
SCENARIO III
You have been treating a periodontitis patient with high doses of a specific antibiotic for a period of several weeks. The gingival inflammation is considerably better and the suppuration has been eliminated, but now the patient complains of joint and skin pain. Because you suspect that the antibiotic is the villain, you suspend the antibiotic therapy. However, even weeks after, the patient continues to complain of joint and skin pain. You have a complete immunology laboratory at your disposal and you begin the evaluate the patient.
Multiple Choice (choose the best answer)
A 21.You perform a skin biopsy and discover that active complement components are present in antibody-antigen complexes. The cellular infiltrate is predominantly…
a.neutrophil.
b.plasma cell.
c.T-cell.
d.NK cell.
e.None of the above.
E 22.You do a renal function test and discover that the kidneys are not functioning to their full capacity. You believe that this is due to
a.blockage of the kidneys with eosinophils
b.the patient not drinking enough water.
c.urinary tract infection.
d.a and c
e.None of the above.
E 23.After several weeks, the patient reports that his symptoms have disappeared. Out of curiosity you obtain a blood sample and find…
a.no anti-antibiotic antibodies in the serum.
b.no anti-antibiotic antibodies in the serum.
c.immune complexes in the serum.
d.a new test question.
e.None of the above.
A 24.The antibiotic caused this problem in your patient because…
a.it functioned as a hapten and became immunogeneic.
b.it stimulated macrophages.
c.it shared a common epitope with a serum protein.
d.it had adjuvant properties.
e.None of the above.
A 25.You administer the same drug with the same regimen to the patient several years later. What do you expect will happen?
a.Same thing, maybe faster due to the booster response.
b.Nothing, ‘cause lightning don’t strike twice in the same place.
c.Nothing, ‘cause the drug wasn’t the problem the first time.
d.I can’t make predictions, ‘cause there’s not enough information given.
e.None of the above.
Non-SCENARIO Questions
A 26.You have developed a compound that blocks the ability of a virus to adhere to the mucosal lining of the respiratory tract. It is effective in protecting you against a large number of viruses, but not all. What do you suspect?
a.It may induce antibodies to non-specific virus receptors.
b.It probably blocks the receptors of specific viruses, but some viruses use different receptors.
c.I don’t suspect anything.
d.A and B
e.None of the above.
E 27.You wish to prepare antibodies to an antigen which appears to be a very poor immunogen. You have repeatedly attempted to immunize a rabbit with this antigen and have had no success in raising any antibody. What do you try next to get this antibody?
a.I would try feeding the rabbit so he doesn’t die this time (don’t pick this).
b.I would try to activate the rabbit’s complement system.
c.I would try to find an atopic rabbit with abnormal immunity.
d.I would try to immunize the innate immune system.
e.None of the above.
A 28.You have obtained a bottle of rabbit antibody from a colleague and find that the affinity of the antibody is too low to work in your assay. Having just learned about affinity maturation, you believe that like good wine, rabbits gets better with time. You put the original immunized rabbit into your wine cellar and retest his antibody affinity several weeks later. What do you expect regarding the affinity of his antibody now?
a.It has gotten better.
b.It has gotten worse.
c.It has turned blue.
d.It has not changed.
e.None of the above.
C 29.You suffer from atopic hypersensitivity and are told to use a mast cell stabilizer for your allergies. Why?
a.Mast cells are a major source of complement components.
b.Histamine is a product of the MHC.
c.If you can prevent degranulation of Mast cells you don't have to worry about the release of substances that cause anaphylaxis.
d.Histamine is a substance released by red blood cells casing many of the symptoms associated with allergies.
e.None of the above.
D 30.The long lag phase in the primary immune response is caused by…
a.earth, wind and fire.
b.hook, line and sinker.
c.Breakfast, lunch and dinner.
d.clonal selection, expansion and maturation.
e.None of the above
SCENARIO IV
The patient who just sat down in your chair tells you that she has no family history of atopy, but she thinks that she might be allergic to milk because she gets sick to her stomach whenever she drinks it. She has elevated levels of IgE in her serum. You notice that there is an inflamed image of a watch on her wrist and when asked, she tells you that always happens when she wears cheap jewelry.
True/False (Please use “a” for true and “b” for false on your answer sheet)
T 31.It is unlikely that this patient has a predisposition to be atopic based on your knowledge of the family history.
T 32.It is likely that this patient has a predisposition to be atopic based on your knowledge of the serum IgE levels.
F 33.The inflammation associated with the watch is probably caused by granulomatous hypersensitivity and mediated by sensitized Mast cells.
T 34.Based on the information provided, there is no way to tell if the reaction that she has to milk is due to atopy.
T 35.It is likely that the reaction to the watch was a result of a hapten-carrier phenomenon.
Non-SCENARIO Questions
F 36.ABO blood group differences between mother and fetus do not cause problems because the naturally-occurring hemagglutinins are of the IgM class, which pass through the placental barrier.
T 37.The Arthus reaction occurs when specific antibody is present at high levels and a small amount of antigen precipitates at the site of local injection
F 38.The specificity of the natural killer cell for tumor cells and virally-infected cells is determined following antigen exposure.
F 39.Antibody-dependent cellular cytotoxicity is mediated by NK cells and is a result of complement receptors on their surface.
T 40.Programmed cell death is thought to be triggered by cytotoxic T-cells and results in the death of target cells.
SCENARIO V
It is your responsibility to manage a patient who has just received total body irradiation and chemotherapy to eliminate his leukemia. The treatment has destroyed all of his white cells and all precursor cells in his bone marrow. He has no immunity at all. This treatment was then followed by a bone marrow transplant from an unrelated, matched donor to reconstitute his bone marrow and immunity. The transplant appears to be successful (with the exception of the monocyte counts), but you notice that your patient is incapable of mounting immune responses to viruses and bacteria. You are asked to figure out what is going on.
Multiple Choice (choose the best answer)
A 41.You suspect that the failure in immune reactivity may be due to lack of antigen presenting cells because…
a.monocytes are key antigen presenting cells.
b.neutrophils are key antigen presenting cells.
c.immunity to viruses and bacteria does not require T cell participation.
d.All of the above.
e.None of the above.
C 42.You decide to perform a FACS analysis on his blood cells to identify the cell populations that are actually present in his circulation. The fluorescent labeled antibodies that you use in the analysis are…
a.prepared against cell surface FM antigens allowing you to identify different white cell subpopulations.
b.prepared against cell surface complement antigens allowing you to identify different white cell subpopulation.
c.prepared against cell surface CD antigens allowing you to identify different white cell subpopulation.
d.All of the above.
e.None of the above.
D 43.The FACS analysis indicates that all of the expected T cell populations are present, but B cells are absent. To confirm this, you measure the level of which proteins in his serum?
a.Albumin
b.Cytokines
c.Transferrin
d.Immunoglobulin
e.None of the above.
E 44.Your suspicions regarding B cells are confirmed and you decide to provide passive immunity (from a horse) to protect this person from tetanus toxin. (The patient just stepped on a rusty nail). What do you expect will happen?
a.You will protect the patient from tetanus, but will induce the Arthus reaction.
b.You will protect the patient from tetanus, but will induce Hashimoto’s thyroiditis.
c.You will not protect the patient from tetanus, but will induce serum sickness .