Quiz Answers
- Toxoplasma gondii is an intracellular parasite that lives inside phagocytic and nonphagocytic cells by generating its own intracellular vesicle. This may allow it to avoid recognition and killing by CD8+ lymphocytes, which require the presentation of foreign peptides transported into the endoplasmic reticulum and loaded onto MHC molecules that have
- a. a beta2 domain instead of a beta 2 microglobulin
- b. a single transmembrane domain ✔
- c. invariant chains
- d. two similar chains
- e. a peptide-binding groove
- Each of the following statements concerning class II MHC proteins is correct EXCEPT:
- a. They are involved in the presentation of antigen by macrophages.
- b. They are found on the surface of both B and T cells. ✔
- c. They have a high degree of polymorphism.
- d. They have a binding site for CD4 proteins.
- Macrophages are major source of:
- a. IL-5
- b. IFN-γ
- c. IL-1 ✔
- d. IL-7
- A patient skin-tested with purified protein derivative (PPD) to determine previous exposure to Mycobacterium tuberculosis develops induration at the skin test site 48 hours later. Histologically, the reaction site would MOST probably show:
- a. Eosinophils
- b. Neutrophils
- c. Helper T cells and macrophages ✔
- d. B cells
- Each of the following statements concerning immunologic tolerance is correct EXCEPT:
- a. Tolerance is more easily induced in T cells than in B cells.
- b. Tolerance is not antigen-specific (i.e., paralysis of the immune cells results in a failure to produce a response against many antigens). ✔
- c. Tolerance is more easily induced by simple molecules than by complex ones.
- d. Tolerance is more easily induced in neonates than in adults.
- Which one of the following substances is NOT released by activated helper T cells?
- a. Interleukin-2
- b. Interleukin-4
- c. Gamma interferon
- d. Alpha interferon ✔
- Cytotoxic T cells induced by infection with virus A will kill target cells:
- a. Infected by virus A and identical at class I MHC loci of the cytotoxic T cells ✔
- b. From the same host infected with any virus
- c. Infected with a different virus and identical at class II MHC loci of the cytotoxic cells
- d. Infected with a different virus and identical at class I MHC loci of the cytotoxic cells
- e. Infected by virus A and identical at class II MHC loci of the cytotoxic T cells
- Antigen-presenting cells that activate helper T cells must express which one of the following on their surfaces?
- a. Class I MHC antigens
- b. Class II MHC antigens ✔
- c. Gamma interferon
- d. IgE
- Your patient is a child who has no detectable T or B cells. This immunodeficiency is most probably the result of a defect in
- a. The membrane attack complex of complement
- b. T cell–B cell interaction
- c. Stem cells originating in the bone marrow ✔
- d. The thymus
- Which category of hypersensitivity BEST describes hemolytic disease of the newborn caused by Rh incompatibility?
- a. Immune complex
- b. Atopic or anaphylactic
- c. Delayed
- d. Cytotoxic ✔
- Wheal and flare is which type of hypersensitivity reaction?
- a. Type V
- b. Type IV
- c. Type I ✔
- d. Type II
- Mediated through allergen specific IgE A patient with severe asthma gets no relief from antihistamines. The symptoms are MOST likely to be caused by:
- a. Interleukin-2
- b. Bradykinin
- c. Serotonin
- d. Slow-reacting substance A (leukotrienes) ✔
- A patient with a central nervous system disorder is maintained on the drug methyldopa. Hemolytic anemia develops, which resolves shortly after the drug is withdrawn. This is MOST probably an example of:
- a. Atopic hypersensitivity
- b. Immune-complex hypersensitivity
- c. Cell-mediated hypersensitivity
- d. Cytotoxic hypersensitivity ✔
- Type I hypersensitivity includes all of the following except:
- a. Hay fever
- b. Extrinsic asthma
- c. Anaphylaxis
- d. Autoimmune hemolytic anemia ✔
- Bone marrow transplantation in immunocompromised patients presents which major problem?
- a. Potentially lethal graft-versus-host disease ✔
- b. Inability to use a live donor
- c. High risk of T-cell leukemia
- d. Delayed hypersensitivity
- A 40-year-old woman has a history of chronic inflammation of the small joints of the hands bilaterally. You suspect rheumatoid arthritis. Which one of the following statements is the MOST accurate regarding the pathogenesis of this disease?
- a. It is caused by antibody against human IgG-forming immune complexes within the joints.
- b. It is caused by superantigens inducing the release of large amounts of lymphokines from helper T cells within the joints. ✔
- c. It is caused by the release of mediators from mast cells when environmental agents cross-link adjacent IgEs within the joints.
- d. It is caused by sensitized CD4-positive T lymphocytes and macrophages invading the joints.
- Type I hypersensitivity is mediated by which of the following immunoglobulins?
- a. IgG
- b. IgM
- c. IgA
- d. IgE ✔
- The principal difference between cytotoxic (type II) and immune complex (type III) hypersensitivity is:
- a. The class (isotype) of antibody
- b. Whether the antibody reacts with the antigen on the cell or reacts with antigen before it interacts with the cell ✔
- c. The participation of complement
- d. The participation of T cells
- A child stung by a bee experiences respiratory distress within minutes and lapses into unconsciousness. This reaction is probably mediated by:
- a. IgG antibody
- b. IgM antibody
- c. Sensitized T cells
- d. Complement
- e. IgE antibody ✔
- A 4-year-old boy presents to his pediatrician with intense perianal itching. His mother explains that the child has also been extremely irritable during the day and has not been sleeping well at night. Eggs with a flattened side were identified by the laboratory technician from a piece of scotch tape brought in by the parent. Infection with which of the following organisms is most likely?
- a. Ascaris lumbricoides
- b. Entamoeba histolytica
- c. Echinococcus granulosus
- d. Enterobius vermicularis ✔
- e. Trichuris trichiura
- Each of the following statements concerning sleeping sickness is correct EXCEPT:
- a. Sleeping sickness is caused by a trypanosome.
- b. Sleeping sickness occurs primarily in tropical Africa.
- c. Sleeping sickness can be diagnosed by finding eggs in the stool. ✔
- d. Sleeping sickness is transmitted by tsetse flies.
- An HIV-positive patient with a CD4+ count of 47 presents with diarrhea. Acidfast structures are found in the stool. From this finding, which of the following is true?
- a. Infection is short lasting and self-resolving and requires no treatment
- b. Even with the best treatment, the infection may be unrelenting ✔
- c. If treated with antibiotics, the infection should resolve in 3-6 days
- d. Infection will resolve only with a combination of antituberculous drugs, and then it may take weeks
- e. Infection could have been prevented by avoiding cat feces and undercooked or raw meat
- Each of the following statements concerning Toxoplasma gondii is correct EXCEPT:
- a. T. gondii can be transmitted across the placenta to the fetus.
- b. T. gondii can cause encephalitis in immunocompromised patients.
- c. T. gondii can be transmitted by cat feces.
- d. T. gondii can be diagnosed by finding trophozoites in the stool. ✔
- A 35-year-old captain in the army reserves has been plagued by a painful, erosive lesion near his ear lobe since his return from Operation Desert Storm several years ago. He denies exposure to the toxic byproducts of burning oil fields. Punch biopsy of the leading edge of the erosion reveals macrophages distended with oval amastigotes. How was this infection acquired?
- a. Bite of Anopheles mosquito
- b. Bite of tsetse fly
- c. Bite of reduviid bug
- d. Fecal contamination of food
- e. Contact with contaminated drinking water
- f. Bite of sandfly ✔
- Each of the following statements concerning Ascaris lumbricoides is correct EXCEPT:
- a. A. lumbricoides is one of the largest nematodes.
- b. Both dogs and cats are intermediate hosts of A. lumbricoides. ✔
- c. A. lumbricoides is transmitted by ingestion of eggs.
- d. A. lumbricoides can cause pneumonia.
- Each of the following statements concerning Trichomonas vaginalis is correct EXCEPT:
- a. T. vaginalis is transmitted sexually.
- b. T. vaginalis causes bloody diarrhea. ✔
- c. T. vaginalis can be diagnosed by visualizing the trophozoite.
- d. T. vaginalis can be treated effectively with metronidazole.
- Each of the following statements concerning hookworm infection is correct EXCEPT:
- a. Hookworm infection can be diagnosed by finding the trophozoite in the stool. ✔
- b. Hookworm infection is caused by Necator americanus.
- c. Hookworm infection is acquired by humans when filariform larvae penetrate the skin.
- d. Hookworm infection can cause anemia.
- Each of the following statements concerning kala-azar is correct EXCEPT:
- a. Kala-azar is transmitted by the bite of sandflies.
- b. Kala-azar can be diagnosed by finding amastigotes in bone marrow.
- c. Kala-azar occurs primarily in rural Latin America. ✔
- d. Kala-azar is caused by Leishmania donovani.
- Mature cyst of Entamoeba histolytica is:
- a. binucleate
- b. quadrinucleate ✔
- c. uninucleate
- d. octanucleate
- The mother of a 4-year-old child notes that her child is sleeping poorly and scratching his anal area. You suspect the child may have pinworms. Which one of the following is the BEST method to make that diagnosis?
- a. Examine the stool for the presence of trophozoites
- b. Examine transparent adhesive tape for the presence of eggs ✔
- c. Examine the stool for the presence of cysts
- d. Determine the titer of IgE antibody against the organism
- e. Examine a blood smear for the presence of microfilaria
- Infective stage of Entamoeba histolytica is:
- a. trophozoite
- b. quadrinucleate cyst ✔
- c. sporozoite
- d. filariform larvae
- Each of the following statements concerning Schistosoma haematobium is correct EXCEPT:
- a. Snails are intermediate hosts of S. haematobium.
- b. S. haematobium infection predisposes to bladder carcinoma.
- c. S. haematobium eggs have no spine. ✔
- d. S. haematobium is acquired by humans when cercariae penetrate the skin.
- Each of the following parasites is transmitted by mosquitoes EXCEPT:
- a. Wuchereria bancrofti
- b. Plasmodium falciparum
- c. Plasmodium vivax
- d. Leishmania donovani ✔
- At a school nurse’s request, a clinic in rural South Carolina sees a 9-year-old girl who appears listless and inattentive, although hearing and visual testing has been within normal limits. The physician finds the child thin, with the “potbelly” of malnutrition, and orders a fecal exam and CBC. The CBC reveals a microcytic, hypochromic anemia, and the fecal exam detects brown, oval nematode eggs approximately 65 microns in size, too numerous to count. What was the most likely means by which this child was infected?
- a. Ingestion of ova
- b. Mosquito transmission of sporozoites
- c. Skin penetration by larvae ✔
- d. Ingestion of larvae
- e. Ingestion of cysts in muscle
- Each of the following statements concerning hydatid cyst disease is correct EXCEPT:
- a. The disease occurs primarily in tropical Africa. ✔
- b. The disease is caused by Echinococcus granulosus.
- c. The disease is caused by a parasite whose adult form lives in dogs’ intestines.
- d. The cysts occur primarily in the liver.
- Each of the following statements concerning Diphyllobothrium latum is correct EXCEPT:
- a. D. latum has operculated eggs.
- b. D. latum is transmitted by undercooked fish.
- c. D. latum is a tapeworm that has a scolex with a circle of hooks. ✔
- d. D. latum causes a megaloblastic anemia due to vitamin B12 deficiency.
- A 24-year-old primiparous woman in her eighth month of gestation develops a positive IgM titer to Toxoplasma gondii for the first time. She should be advised by her physician that
- a. retinochoroiditis can be prevented by drug treatment of an infant with a positive IgM response ✔
- b. future infections can be avoided by proper vaccination and worming of cats
- c. a newborn with a positive anti-Toxoplasma IgG response should be treated with anti-parasitics
- d. major organ damage can be reversed by prompt treatment of the newborn this child and all future fetuses are likely to be infected
- Each of the following parasites passes through the lung during human infection EXCEPT:
- a. Wuchereria bancrofti ✔
- b. Ascaris lumbricoides
- c. Necator americanus
- d. Strongyloides stercoralis
- Each of the following parasites is transmitted by eating inadequately cooked fish or seafood EXCEPT:
- a. Clonorchis sinensis
- b. Paragonimus westermani
- c. Ancylostoma duodenale ✔
- d. Diphyllobothrium latum
- Laboratory diagnosis of a patient with a suspected liver abscess due to Entamoeba histolytica should include:
- a. Stool examination and indirect hemagglutination test ✔
- b. Indirect hemagglutination test and skin test
- c. Xenodiagnosis and string test
- d. Stool examination and blood smear
- Children at day care centers in the United States have a high rate of infection with which one of the following?
- a. Necator americanus
- b. Enterobius vermicularis ✔
- c. Entamoeba histolytica
- d. Ascaris lumbricoides
- Mosquitoes is/are the vector in the following disorder(s)
- a. Onchocerciasis
- b. Bancroftian filariasis ✔
- c. African trypanosomiasis
- d. Visceral leishmaniasis
- The main anatomic location of Schistosoma mansoni adult worms is:
- a. Lung alveoli
- b. Renal tubules
- c. Bone marrow
- d. Intestinal venules ✔
- A 13-year-old boy from India was brought to the emergency room with a prolapsed rectum. Examination of the rectum reveals small worms that resemble whips attached to the mucosa. A stool sample reveals eggs that are barrel shaped, with bipolar plugs. Which of the following is the most likely cause?
- a. Echinococcus granulosus
- b. Entamoeba histolytica
- c. Enterobius vermicularis
- d. Trichuris trichiura ✔
- e. Ascaris lumbricoides
- f. Giardia lamblia
- Which one of the following statements concerning immunoglobulin allotypes is CORRECT?
- a. Allotypes are confined to the variable regions.
- b. Allotypes are found only on heavy chains.
- c. Allotypes are due to genetic polymorphism within a species. ✔
- d. Allotypes are determined by class I MHC genes.
- The MOST important protective function of the antibody stimulated by tetanus immunization is:
- a. To opsonize the pathogen (Clostridium tetani)
- b. To prevent growth of the pathogen
- c. To neutralize the toxin of the pathogen ✔
- d. To prevent adherence of the pathogen
- Inactivation of a toxin by an antibody is termed:
- a. Opsonization
- b. Neutralization ✔
- c. Lyophilization
- d. Lysis
- e. Attenuation
- An epitope is
- a. the antigen determinant site ✔
- b. a B-cell
- c. an antibody
- d. a hapten
- Which of the following antibodies have a positive effect on babies through breast feeding?
- a. IgG
- b. IgA ✔
- c. IgM
- d. IgD
- e. IgE
- Isotypes of Antibodies refer to variations in the:
- a. light chain variable region
- b. heavy chain variable region ✔
- c. heavy chain constant region
- d. light chain constant region