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Exam 8: Immunology

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Question 1

Multiple Choice

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A researcher identifies a group of malignant epithelial cells in the sigmoid colon that have decreased their surface expression of MHC class I antigen.  Which of the following immune effector cell types is most likely to kill the transformed epithelial cells?

A) Neutrophils
B) Macrophages
C) Dendritic cells
D) CD4+ T lymphocytes
E) Plasma cells
F) Natural killer cells

G) A) and B)
H) A) and C)

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Question 2

Multiple Choice

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On flow cytometric analysis of a sample of fetal thymus, a certain population of cells is identified that is positive for both CD4 and CD8 cell surface antigens.  These cells are best characterized as which of the following cells?

A) Immature cortical T lymphocytes
B) Mature cytotoxic T lymphocytes
C) Mature helper T lymphocytes
D) Antigen presenting cells
E) Natural killer (NK) cells
F) Thymic epithelial cells

G) B) and C)
H) C) and E)

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Question 3

Multiple Choice

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A 3-month-old girl is brought to the emergency department due to fever, irritability, and vomiting for the past 2 days.  On examination, she is ill-looking, lethargic, and febrile.  Blood cultures grow Mycobacterium tuberculosis.  One of her brothers died from disseminated mycobacterial infection during infancy.  Impairment of which of the following protective mechanisms is most likely contributing to this patient's infection?

A scientist is interested in the mechanisms by which leukocytes traffic to sites of inflammation and infection.  She finds that endothelial cells increase the expression of certain cell surface molecules in response to cytokines to allow for leukocyte trafficking.  She subsequently creates a knockout mouse that has a deletion in the platelet endothelial cell adhesion molecule 1 (PECAM-1) gene.  The protein product of this gene is mainly localized to specific areas on the endothelial cells.  Absent expression of this gene will most likely affect which of the following neutrophil functions?

A 45-year-old man comes to clinic for routine follow-up.  He has a history of end-stage renal disease due to autosomal dominant polycystic kidney disease, and he underwent a deceased-donor kidney transplant 4 years ago.  The patient has hypertension that initially resolved following the transplant but redeveloped 6 months ago.  Review of his recent laboratory studies reveals a progressive increase in serum creatinine levels over the last few months.  Urinalysis is within normal limits.  On ultrasonography, the transplanted kidney is reduced in size.  A biopsy of the graft is most likely to show which of the following?

A 34-year-old woman comes to the physician for a follow-up visit.  She was diagnosed with rheumatoid arthritis 3 months ago and started on methotrexate therapy.  Despite treatment, she continues to have several hours of morning stiffness daily and frequently awakens at night due to joint pain.  Physical examination shows swelling and tenderness in the joints of her hands and wrists.  Etanercept is subsequently added to her treatment regimen.  This medication is best characterized as which of the following?

A 7-year-old boy is brought to the emergency department by his mother because of difficulty breathing for 20 minutes. He was having lunch with his mother when she noticed a rash and swelling of his tongue and lips. His temperature is 37°C (98.6°F) , pulse is 169/min, respirations are 28/min, and blood pressure is 90/50 mmHg. Pulse oximetry on room air shows an oxygen saturation of 92%. Examination shows generalized hives, swelling of his tongue and lips, and labored breathing with intercostal retractions. Which of the following is most responsible for this patient's current condition?

A 6-year-old boy is being evaluated in the office due to a history of recurrent infections and failure to thrive.  He has been hospitalized for pneumococcal pneumonia twice and has had 5 episodes of otitis media.  The patient also has a history of prolonged diarrhea caused by Giardia intestinalis.  Physical examination shows a lack of tonsillar tissue, as well as minimally palpable cervical, axillary, and inguinal lymph nodes.  Further evaluation shows that the patient has defective signaling between activated CD4 T cells and B cells.  Which of the following laboratory findings are most likely to be found in this patient?

A 19-year-old man comes to the office due to eye pain and blurry vision in both eyes for the last several days.  He sustained an open globe injury to the right eye 3 months ago after being struck during an altercation and was treated with surgical repair and prophylactic antibiotics.  The left eye was unaffected.  At the patient's last follow-up appointment, visual acuity in the right eye had improved from 20/400 to 20/80.  He is otherwise healthy.  Temperature is 37.1 C (98.8 F) .  Examination is unremarkable apart from bilateral conjunctival injection and decreased visual acuity in both eyes.  Analysis of vitreous samples from both eyes demonstrates multinucleated giant cells.  Which of the following mechanisms is most likely causing this patient's current manifestations?

A 56-year-old woman with a history of heart failure is admitted to the hospital for orthotopic cardiac transplantation.  The patient developed biventricular failure due to idiopathic myocarditis.  She has had persistent New York Heart Association class IV symptoms refractory to maximal medical therapy and was placed on the transplant waiting list.  An ABO-compatible cadaveric heart is available for transplant with partial human leukocyte antigen (HL A) mismatch.  Cardiac transplantation is performed and the patient's T lymphocytes quickly recognize the foreign HLA molecules of the transplant cells.  Inhibition of which of the following substances would specifically reduce the proliferation and differentiation of these T lymphocytes?

A 12-month-old boy is evaluated for an eczematous rash.  Medical history is significant for several severe respiratory infections that required hospitalization.  Complete blood count shows white blood cells at 9,000/mm³ and platelets at 40,000/mm³.  The platelets seem abnormally small and deformed on the peripheral blood smear.  Which of the following is the most likely diagnosis?

A 13-month-old boy is admitted to the hospital due to diarrhea and dehydration.  Over the past week, the patient has developed severe, watery diarrhea and has had poor oral intake.  Medical history includes multiple episodes of bronchiolitis and, at age 8 months, an intensive care unit admission due to pneumococcal pneumonia requiring a brief period of mechanical intubation and chest tube placement.  The parents say that he has been growing poorly over the past 6 months despite feeding well and supplemention with high-calorie formulas.  On examination, the patient appears lethargic with sunken eyes and poor skin turgor, as well as moderate tachycardia and tachypnea.  As part of the laboratory evaluation, flow cytometry of in vitro-stimulated CD4⁺ T cells reveals a near absence of CD40 ligand.  Which of the following additional findings is most likely associated with this patient's condition?

A 58-year-old woman comes to the emergency department due to abdominal discomfort and bloating.  Physical examination reveals ascites.  Abdominal ultrasonography shows a mass in the left ovary, and subsequent paracentesis reveals malignant cells.  Surgical excision of the mass is performed.  Histopathology shows high-grade serous carcinoma composed of atypical cells with pleomorphic nuclei and mitotic figures.  Large numbers of T cells are present in the tumor stroma; further evaluation shows the tumor expresses PD-1 ligands that interact with the PD-1 receptor on the infiltrating T cells.  Which of the following is most likely occurring in the tumor microenvironment as a result of this interaction?

Researchers are investigating the use of immune checkpoint inhibitors for the treatment of advanced colorectal cancer.  They find that this therapy is more effective in patients with DNA mismatch-repair deficiency compared to patients with an intact mismatch-repair mechanism.  Which of the following most likely explains the improved efficacy of the drug in the first group of patients?

A 23-year-old woman comes to the emergency department because of a diffuse, itchy rash and swollen face for 6 hours. That morning, she was diagnosed with an abscess of the lower leg. She underwent treatment with incision and drainage as well as oral antibiotics. She has no history of serious illness. She is not in acute distress. Her temperature is 37.2°C (99°F) , pulse is 78/min, and blood pressure is 128/84 mm Hg. Physical examination shows mild swelling of the eyelids and lips. There are multiple erythematous patches and wheals over her upper extremities, back, and abdomen. The lungs are clear to auscultation. Which of the following is the most likely cause of this patient's hypotension?

A 40-year-old woman, gravida 4 para 4, comes to the clinic due to anemia.  A week ago, the patient was seen in the emergency department due to fatigue, shortness of breath, and increasingly heavy, irregular menses.  Laboratory evaluation showed a hemoglobin level of 5.4 g/dL.  After a transfusion with packed red blood cells, her follow-up hemoglobin level was 7.8 g/dL prior to discharge.  Since then, the patient's energy and breathing have improved, and she has had no further menstrual bleeding.  However, yellowing of the eyes and face has developed over the last day.  Vital signs are normal.  Examination reveals scleral icterus.  There is no hepatosplenomegaly.  Laboratory results are as follows: This patient's current symptoms are most likely due to which of the following antibody-antigen reactions?

The acidification of lysosomes within antigen presenting cells is prevented in an experimental setting.  The affected cells show impaired interaction with T lymphocytes upon antigen exposure.  The observed effect most likely results from a low cell surface expression of which of the following molecules?

A 6-month-old boy is brought to the clinic by his mother and grandmother for a routine well-child visit.  The child was born full-term and has no medical problems.  He recently learned to sit with support and is starting to eat pureed foods.  Vital signs and physical examination are normal.  As part of the routine pediatric immunization schedule, the pneumococcal conjugate vaccine is ordered.  The patient's grandmother says that she recently received the pneumococcal polysaccharide vaccine.  Which of the following statements is true regarding the difference between the pneumococcal conjugate and polysaccharide vaccines?

A 3-year-old boy experiences recurrent sinusitis and an episode of severe pneumonia.  As part of his evaluation, Candida extract is injected intradermally.  Forty-eight hours later, he returns to the clinic with a firm nodule measuring 16 mm in diameter where the extract was injected.  Which of the following cell types is most likely responsible for the reaction observed in this patient?

A 34-year-old woman with end-stage kidney disease secondary to IgA nephropathy is undergoing kidney transplant from an unrelated living donor.  The patient receives induction immunosuppression with a rabbit antithymocyte globulin-based regimen immediately prior to the procedure.  The surgery is performed without complications, and maintenance immunosuppressive therapy is begun.  Ten days later, the patient experiences high fevers, generalized pruritic rash, and pain, redness, and swelling of the bilateral metacarpophalangeal joints, wrists, and knees.  The erythrocyte sedimentation rate is elevated.  Arthrocentesis of the involved joint yields synovial fluid with neutrophilic leukocytosis; there are no crystals and no bacteria on Gram stain.  Which of the following is most likely responsible for the increased synovial membrane permeability in this patient?