Question 1

A 15-year-old healthy girl with no major medical problems notes blotchy areas of erythema that are pruritic over the skin of her arms, legs, and trunk within an hour every time she eats seafood, followed by diarrhea. These problems abate within 3 hours, and then physical examination reveals no abnormal findings. Which of the following immunologic abnormalities is she most likely to have?

A Localized anaphylaxis

B Cell-mediated hypersensitivity

C Complement activation

D Hypergammaglobulinemia

E Immune complex deposition

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Question 2

A 55-year-old man has developed progressive renal failure for the past 5 years. Microscopic examination of a renal biopsy shows extensive glomerular and vascular deposition of pink amorphous material on H&E staining. This material demonstrates apple-green birefringence under polarized light after Congo red staining. Immunohistochemical staining of these deposits is positive for lambda light chains. Which of the following conditions is most likely to be present in this man?

A Rheumatoid arthritis

B Tuberculosis

C Systemic lupus erythematosus

D Multiple myeloma

E Alzheimer disease

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Question 3

A 22-year-old woman has experienced episodes of myalgias, chest pain, and arthralgias for the past 3 years. On examination a friction rub is audible on chest auscultation and there is dullness to percussion at posterior lung bases. No joint deformity is noted. She has continued working at her job. She has a mild normocytic anemia. A chest x-ray shows bilateral pleural effusions. Which of the following laboratory screening tests is most appropriate to begin the workup for her condition?

A CD4 lymphocyte count

B Blood culture

C Antinuclear antibody test

D Sedimentation rate

E Creatine phosphokinase

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Question 4

A male infant is born at term. No congenital anomalies are noted on examination. A year later he now has failure to thrive and has been getting one bacterial pneumonia after another with both Hemophilus influenzae and Streptococcus pneumoniae cultured from his sputum. Which of the following diseases is he most likely to have?

A DiGeorge syndrome

B Selective IgA deficiency

C Epstein-Barr virus (EBV) infection

D Acute leukemia

E X-linked agammaglobulinemia

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Question 5

A study is performed of outcomes involving patients who received renal allografts. It is noted that patients receiving allografts with matching to the donor by tissue typing for HLA-DR (Class II) antigens have a low rate of complications. Which of the following immunologic abnormalities is most likely to be diminished by tissue typing?

A Amyloidosis

B Cell lysis by CD8 lymphocytes

C Graft versus host disease

D CD4 lymphocyte activation

E Serum sickness

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Question 6

A 5-year-old boy and his 4-year-old brother have had recurrent pneumonia, meningoencephalitis, sinusitis, otitis, and diarrhea since infancy. Bacterial and viral agents have been implicated, as well as Pneumocystis, Giardia, and Cryptosporidium. Laboratory studies show serum IgG 47 mg/dL, IgA 5 mg/dL, and IgM 671 mg/dL. Normal numbers of B and T cells are present. These children are most likely to have a mutation involving a gene encoding for which of the following?

A NADPH oxidase

B Wiskott-Aldrich syndrome protein

C Cytokine receptor common gamma chain

D CD40L

E Complement C1 inhibitor

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Question 7

A 20-year-old woman has had symmetrical, proximal muscle weakness for 6 months. On exam she has 4/5 motor strength in all extremities. A deltoid biopsy shows a neutrophilic infiltrate with focal necrosis of the muscle fibers. Her antinuclear antibody test is negative, but she has histidyl-tRNA synthetase (Jo-1) antibody in her serum. Which of the following additional findings would be most likely be present in this patient?

A Heart failure

B Malabsorption

C Peripheral neuropathy

D Skin rash

E Renal failure

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Question 8

A hypersensitivity response of the immune system is noted to be stimulated by release of IL-4 and IL-5. This is accompanied by eosinophilia. This response is most likely be directed against which of the following?

A Amyloid protein

B Spirochetes

C Neoplasms

D Inhaled dusts

E Liver flukes

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Question 9

A 54-year-old woman has noted that during the past month her fingers become pale and painful upon exposure to cold. On exam she has mild dyspnea, but no wheezing. Her blood pressure is 170/110 mm Hg. Her antinuclear antibody test is positive with a titer of 1:256 and a nucleolar pattern. Her serum urea nitrogen is 15 mg/dL with creatinine of 1.1 mg/dL. Which of the following autoimmune diseases is she most likely to have?

A Discoid lupus erythematosus (DLE)

B Systemic sclerosis

C Polymyositis-dermatomyositis

D Sjogren's syndrome (SS)

E Rheumatoid arthritis (RA)

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Question 10

Twelve hours after going on a hike through dense foliage, a 40-year-old man notices a slightly raised and tender irregular reddish rash on one forearm that was not covered by clothing. This rash gradually increases in intensity for 2 days and then fades away after two weeks. Which of the following forms of immunologic hypersensitivity is most likely demonstrated in this patient?

A Type I hypersensitivity

B Type II hypersensitivity

C Type III hypersensitivity

D Type IV hypersensitivity

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Question 11

A 30-year-old woman has experienced myalgias for the past 3 months. On physical examination she has 5/5 motor strength in all extremities. She has dullness to percussion at lung bases. A chest x-ray shows bilateral pleural effusions. Laboratory studies show a positive antinuclear antibody test at a titer of 1:1024. Her serum urea nitrogen is 30 mg/dL. A renal biopsy is performed and microscopic examination shows a granular pattern of immunofluorescence staining with antibody to complement component C1q. This pattern is most typically produced as a consequence of which of the following immunologic mechanisms?

A IgE coating mast cells

B Antiglomerular basement membrane antibody

C Antigen-antibody complexes

D Macrophage release of lymphokines

E Release of prostaglandins

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Question 12

The second pregnancy for a 23-year-old woman appears uncomplicated until ultrasound performed at 19 weeks shows hydrops fetalis. The fetal organ development is consistent for 19 weeks, and no congenital anomalies are noted. Her first pregnancy was uncomplicated and resulted in the birth of a normal girl at term. The current pregnancy ends with birth of a baby boy at 32 weeks gestation. On examination the baby has marked icterus. Laboratory studies show a hemoglobin of 7.5 g/dL, and neonatal exchange transfusion is performed. Which of the following immunologic mechanisms best explains this infant's findings?

A Anti-receptor antibody

B Loss of self tolerance

C Immune complex formation

D Delayed type hypersensitivity

E Complement mediated cell destruction

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Question 13

A previously healthy 12-year-old girl develops a sore throat over the past 2 days. On physical examination she has marked pharyngeal erythema with overlying yellowish exudate. A throat culture grows group A beta-hemolytic Streptococcus. Her pharyngitis resolves, but 3 weeks later she develops chest pain along with fever and malaise. The girl describes aching of her knees, hips, shoulders, and elbows. Multiple subcutaneous skin nodules are noted on physical examination, and she exhibits slight shaking movements of her head and neck. Her antistreptolysin-O and anti-DNAse B titers are elevated. Her creatine kinase MB fraction is elevated. Her findings are most likely the result of which of the following immunologic mechanisms?

A Bypass of low-zone tolerance through cross-reactivity

B Deposition of antigen-antibody complexes in multiple tissue

C Formation of an antibody to immune complexes

D Exposure of a previously sequestered antigen

E Interaction between genetic predisposition and environmental insults

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Question 14

A 60-year-old woman has developed crippling arthritis over the past 20 years. On physical examination the arthritis primarily involves her hands and feet, with marked joint deformities characterized by ulnar deviation and swan-neck deformities of her fingers. She has an irregular heart rate. Laboratory studies show that her rheumatoid factor titer is markedly elevated, but her antinuclear antibody test is negative. A rectal biopsy shows submucosal deposition of pink amorphous material that stains positively with Congo red. Which of the following precursor proteins most likely gave rise to these deposits?

A Serum amyloid-associated protein

B Lambda immunoglobulin light chains

C Transthyretin

D Amyloid precursor protein

E Beta-2-microglobulin

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Question 15

A 35-year-old man has experienced a malar skin rash, polyarthritis with swelling and warmth of his hands, and sensitization to cold for the past 6 months. On physical examination he has generalized lymphadenopathy and pale conjunctivae. Laboratory findings include a hemoglobin of 9.5 g/dL, total WBC count of 2100/microliter, total serum protein 8.8 g/dL, albumin 3.6 g/dL, creatinine 1.1 mg/dL, and creatine kinase of 468 U/L. His antinuclear antibody test is positive at 1:256. Which of the following additional serologic tests is most likely to determine his underlying disease process?

A Anti-centromere

B Anti-RNP

C Rheumatoid factor

D Serum C1q complement level

E HIV test

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Question 16

A 48-year-old man has had a chronic cough with fever for 2 months. On physical examination his temperature is 37.9°C. A chest radiograph reveals a diffuse bilateral reticulonodular pattern. A transbronchial biopsy is performed and microscopic examination shows focal areas of inflammation containing epithelioid macrophages, Langhans giant cells, and lymphocytes. These findings are most typical for which of the following immunologic responses?

A Type I hypersensitivity

B Type II hypersensitivity

C Graft versus host disease

D Polyclonal B-cell activation

E Type IV hypersensitivity

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Question 17

A 9-year-old boy has a sore throat. A throat culture grows group A hemolytic streptococcus. He receives antibiotic therapy. However, 17 days later he develops dark-coloured urine. Laboratory studies show 3+ blood on urinalysis. A renal biopsy is performed. On immunofluorescence staining the biopsy shows granular deposition of IgG and complement around glomerular capillary loops. Which of the following immune hypersensitivity mechanisms is most likely responsible for this pattern of findings?

A Type I

B Type II

C Type III

D Type IV

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Question 18

A 40-year-old woman has had increasing difficulty swallowing for over the past year. She also notes that it is more difficult to use the keyboard of her computer because she finds it hard to move her fingers, though the joints are not painful. She has lost the facial wrinkles that she was beginning to develop in middle age. A skin biopsy is performed and shows extensive dermal fibrosis but almost no inflammatory cell infiltrates. These findings are most typical for which of the following conditions?

A Mixed connective tissue disease

B Discoid lupus erythematosus

C Limited systemic sclerosis

D Dermatomyositis

E Secondary amyloidosis

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Question 19

A 28-year-old woman is given intravenous penicillin to treat infective endocarditis. Within minutes of starting this therapy, she begins to have severe difficulty breathing with respiratory stridor and tachypnea. She suddenly develops an erythematous skin rash over most of her body. Her symptoms are most likely to be produced by release of which of the following chemical mediators?

A Interleukin 1

B Bradykinin

C Complement C5a

D Histamine

E Thromboxane

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Question 20

A 42-year-old man has lost 7 kg over the past two years. During that time he has had pain and swelling around the small joints of his hands and feet. He has had a series of upper respiratory tract infections, with organisms including Staphylococcus aureus, Streptococcus pneumoniae, and Pseudomonas aeruginosa cultured. He has a chronic diarrhea. A stool specimen is found to have Giardia lamblia cysts. Laboratory studies show a hemoglobin of 8.8 g/dL with a reticulocyte count of 3.2%. His serum urea nitrogen is 17 mg/dL with creatinine 1.0 mg/dL. His antinuclear antibody test is negative. Quantitative serum immunoglobulins show IgA 70 mg/dL, IgG 303 mg/dL, and IgM 64 mg/dL. By flow cytometry there are normal numbers of T cells and slightly reduced numbers of B cells. Which of the following conditions is most likely to be present in this man?

A HIV infection

B Polymyositis

C Bruton agammaglobulinemia

D Common variable immunodeficiency

E Diabetes mellitus

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Question 21

A 31-year-old woman has noted chest pain for the past week. On physical examination she has decreased breath sounds with dullness to percussion at lung bases. A chest radiograph shows modest bilateral pleural effusions. On chest CT scan, the pleural effusions, as well as a pericardial effusion, are seen. A thoracentesis on the left yields clear fluid with a low protein and cell count. She is found to have an anti-double stranded DNA titer of 1:512. If she is later found to have a serum urea nitrogen that is 55 mg/dL, it will most likely be the result of which of the following pathologic processes?

A Atherosclerosis

B Immune complex deposition

C Amyloid deposition

D Vascular chronic inflammation

E Anti-glomerular basement membrane antibody

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Question 22

A 28-year-old woman undergoes allogeneic bone marrow transplantation for acute leukemia. There is a 5/6 HLA match. Three weeks later, she has marrow engraftment and her hemoglobin and WBC count are returning to normal. However, she has the appearance of a fine, scaling skin rash over her trunk and upper extremities. These findings are most consistent with which of the following complications?

A Reduced numbers of megakaryocytes

B Keratinocyte apoptosis

C Dry gangrenous necrosis

D Contact dermatitis

E Abrasions from a fight in the ICU

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Question 23

A 22-year-old woman is bothered by an erythematous rash involving her cheeks and nose every time she spends more than a few minutes outdoors on a sunny day. On physical examination between these episodes, there are no abnormal findings. A biopsy of the skin involved with the rash shows deposition of IgG along the basement membrane by immunofluorescence microscopy, but uninvolved skin does not demonstrate this IgG deposition. Her antinuclear antibody test is negative. She has no other complaints. Her renal function tests are normal. Which of the following is the most likely diagnosis?

A Discoid lupus erythematosus

B Systemic lupus erythematosus

C Limited systemic sclerosis

D Diffuse systemic sclerosis

E Contact dermatitis

F Atopic dermatitis

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Question 24

A 37-year-old woman develops a malar rash when she spends several hours outside at a Kensington Oval cricket match. Ordinarily, she avoids being in the sun, but a friend provided free tickets to a West Indies test match. When she sees her physician, a urinalysis is performed that shows hematuria and proteinuria. A skin biopsy shows immunofluorescence positivity along the dermal-epidermal junction with antibody to C1q. Which of the following additional complications is she most likely to suffer as a consequence of her underlying disease?

A Pulmonary hemorrhage

B Joint ankylosis

C Nodular glomerulosclerosis

D Pulmonary fibrosis

E Pericarditis

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Question 25

An 11-month-old infant has had upper and lower respiratory tract infections almost continuously since the time of birth, with organisms including Pneumocystis jiroveci and Pseudomonas aeruginosa identified. The baby also has oropharyngeal candidiasis. The baby succumbs to a cytomegalovirus pneumonitis. At autopsy, the thymus is markedly hypoplastic, and lymph nodes throughout the body are small, with absent germinal centers on microscopic examination. Which of the following mechanisms is most likely to explain these findings?

A Adenosine deaminase deficiency

B Failure of B cell maturation to plasma cells

C Human immunodeficiency virus infection

D Autoantibodies to both T and B lymphocytes

E Failure of development of 3rd and 4th pharyngeal pouches

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Question 26

Every springtime, a young healthy man is bothered by episodes of nasal congestion accompanied by sneezing and watery eyes. He has no cough. On physical examination he is afebrile. There is swelling of his nasal passageways, but no other findings. His condition improves with use of loratadine. His problems are most likely produced by release of chemical mediators from which of the following cell types?

A Neutrophil

B Mast cell

C CD4+ cell

D NK cell

E Macrophage

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Question 27

A 28-year-old woman has noted occasional dyspnea for the past 13 months. She has also noted a non-productive cough and mild fever. Her symptoms improve when she is on vacation. A chest radiograph reveals nodular infiltrates. A transbronchial lung biopsy reveals microscopic findings consistent with an extrinsic allergic alveolitis with interstitial infiltrates composed of lymphocytes along with a few neutrophils and eosinophils. Which of the following is most likely to explain her findings?

A Parrots in her house

B Heavy cigarette smoking

C Downwind from a lead smelter.

D Abusing crack cocaine

E Systemic lupus erythematosus.

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Question 28

A 30-year-old man has the sudden onset of fever, cough, and dyspnea. He has lost about 10% of his normal body weight over the past 6 months, along with a chronic, watery diarrhea. A bronchoalveolar lavage is performed, and cysts of Pneumocystis jiroveci are seen in the fluid. He is treated with clotrimoxazole and recovers. He develops pain and decreased vision on the right, and funduscopic examination reveals a cytomegalovirus retinitis; this improves with ganciclovir therapy. He develops tan-yellow plaques on his tongue with Candida albicans. Which of the following laboratory test findings is most likely to be present in this man?

A ANA titer of 1:1024

B Platelet count of 15,000/microliter

C Serum IgA of 10 mg/dL

D CD4 lymphocyte count of 100/microliter

E cANCA titer of 1:256

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Question 29

A 40-year-old woman complains of dry mouth and dry eyes that have become almost constantly irritating during the past 2 years, regardless of her fluid intake or the weather outside. However, her fingers do not turn blue or painful upon exposure to cold. She is found serologically to have autoantibodies to the nuclear antigen SS-A, along with a positive antinuclear antibody test. Which of the following is most likely to be the worst long term complication of her underlying disease?

A Pneumocystis jiroveci pneumonia

B Monoclonal B-lymphocyte proliferation

C Malabsorption with diarrhea

D Diffuse pulmonary interstitial fibrosis

E Glomerulonephritis

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Question 30

A 3-year-old boy has had numerous bacterial infections, including respiratory infections with Hemophilus influenzae, Streptococcus pneumoniae, and Staphylococcus aureus since infancy. He develops a polyarthritis that clears with immunoglobulin therapy. A lymph node biopsy is performed, and microscopically the germinal centers of his nodes are rudimentary. During the 3rd decade of his life he develops systemic lupus erythematosus. He demonstrates skin test positivity to Candida antigen. Laboratory studies show that his serum IgG is 110 mg/dL. His total WBC count is 7650/microliter with differential count of 65 segs, 4 bands, 22 lymphs, and 9 monos. Which of the following immunologic disorders best explains these findings?

A Adenosine deaminase deficiency

B Malformation of 3rd and 4th pharyngeal pouches

C Reduction in CD4 lymphocytes

D Defect in NADPH oxidase

E Failure of B cell maturation into plasma cells

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Question 31

A bee sting is suffered by a 28-year-old man, and his wife searches frantically for the medical kit with the injectable epinephrine. Which of the following immunologic mechanisms are they trying to circumvent?

A Immune complex formation

B Interleukin release from macrophages

C Binding of anti-receptor antibody

D Release of preformed tryptase

E Complement activation

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Questions 32

A 35-year-old man has decreasing mobility of his spine, and he becomes more "hunched over" during the past 5 years. He has hip pain bilaterally. On physical examination he has loss of lumbar lordosis and diminished range of motion at the hips. A radiograph of the pelvis shows ankylosis with sacroiliitis bilaterally. No other joints appear to be affected. His antinuclear antibody test is negative. He has no other significant medical problems. Which of the following laboratory test findings is most likely to be present in this man?

A HLA B27

B ANCA positive at 1:256

C Elevated rheumatoid factor

D Markedly decreased serum complement

E Monoclonal gamma spike

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Question 33

A 44-year-old man has been plagued by mild chronic diarrhea and increased numbers of minor respiratory tract infections for most of his life. Following a motor vehicle accident with multiple lacerations to the lower leg, he has a significant blood loss requiring transfusion of blood products. During the transfusion, he is noted to have an anaphylactic transfusion reaction. Which of the following diseases is he most likely to have?

A Selective IgA deficiency

B Secondary amyloidosis

C Systemic lupus erythematosus

D Common variable immunodeficiency

E Graft versus host disease

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Question 34

A 55-year-old woman has had increasing difficulty with swallowing over the past year. On physical examination her blood pressure is 210/110 mm Hg. Laboratory testing reveals a positive antinuclear antibody test with a nucleolar pattern on immunofluorescence. Her serum complement levels are normal. Which of the following lesions is most likely to be seen in her kidneys with renal biopsy?

A Renal cell carcinoma

B Nodular glomerulosclerosis

C Acute glomerulonephritis

D Hyperplastic arteriolosclerosis

E Polycystic change

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Question 35

A positive tuberculin skin test, with a firm 15 mm diameter dark red firm area of induration on the forearm, appears 60 hours following injection of the purified protein derivative (PPD). This finding is most likely to be a consequence of which of the following types of hypersensitivity reaction?

A Type I hypersensitivity

B Type II hypersensitivity

C Type III hypersensitivity

D Type IV hypersensitivity

E Complement activation

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Question 36

A study of immunofluorescence patterns in skin biopsies is performed. One immunofluorescence pattern with antibody to IgG that shows a band of immunofluorescence at the dermal-epidermal junction. This pattern is most likely to be based upon which of the following pathologic mechanisms?

A CD4 lymphocytes infiltrating the dermis

B Degranulation of mast cells upon allergen contact

C Trapping of antigen-antibody complexes

D Macrophages releasing cytokines

E Neutrophils emigrating from capillaries

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Question 37

A 15-year-old boy underwent bone marrow transplantation for aplastic anemia, with marrow donated from a sibling, with a 5 out of 6 antigen match. He later developed a fine, scaling skin rash as well as a watery diarrhea. Which of the following laboratory test findings is most likely to accompany this patient's disease?

A Hyperamylasemia

B Hyperbilirubinemia

C Hypocomplementemia

D Neutrophilia

E Elevated creatine kinase

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Question 38

A 50-year-old man with end stage renal disease from long-standing diabetes mellitus receives a cadaveric renal transplant. A month later, he has increasing malaise. His urine output decreases. Laboratory studies show a rising serum urea nitrogen and creatinine. The allograft is biopsied and seen microscopically to be undergoing destruction by cells which are recognizing graft cells expressing class I HLA antigens. Which of the following cells is most likely to mediate this response?

A CD4 lymphocyte

B NK cell

C CD8 lymphocyte

D Macrophage

E Plasma cell

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Question 39

Persons infected with HIV are shown to have a period of clinical latency of infection lasting years. During this time their risk for infection by opportunistic pathogens is not increased. However, a reservoir of virus remains within their lymphoid tissues. Which of the following cells is most important to maintain this reservoir of HIV?

A CD8 lymphocyte

B High endothelial venule cell

C Macrophage

D Memory B cell

E NK cell

F Plasma cell

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Question 40

A 21-year-old man with serum IgA of 22 mg/dL, IgG of 175 mg/dL, and IgM of 40 mg/dL has had a high fever with cough productive of yellowish sputum for the past two days. Auscultation of his chest reveals a few crackles in both lung bases. A chest radiograph shows bilateral patchy pulmonary infiltrates. Which of the following inflammatory cell types will most likely be seen in greatly increased numbers in his sputum specimen?

A Macrophage

B Neutrophil

C Mast cell

D Lymphocyte

E Langhans giant cell

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Question 41

A 31-year-old man incurs an injury in an industrial accident, with a steel H-beam striking the right side of his face, crushing the zygomatic arch and damaging the globe of the right eye. He undergoes plastic repair of bone and soft tissues and an attempt is made to salvage the eye. A month later, he has decreased visual acuity in both eyes, with choroidal thickening seen on funduscopic examination. The right eye is enucleated and shows prominent CD4 lymphocyte and macrophage infiltration of the uvea. By which of the following immunologic mechanisms has this condition most likely developed?

A Breakdown of T-cell anergy

B Polyclonal lymphocyte activation

C Release of sequestered antigens

D Cross-reactivity with myocardial antigens

E Failure of T-cell mediated suppression

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Question 42

A neonate born at term developed tetany soon after birth. On physical examination the infant has a heart murmur. Laboratory studies show a serum calcium of 6.3 mg/dL. Echocardiography reveals a membranous intraventricular septal defect. Within the next year, this infant has bouts of Pneumocystis jiroveci pneumonia, Aspergillus fumigatus pneumonia, and parainfluenza virus and herpes simplex virus upper respiratory infections. Which of the following abnormalities most likely explains the development of this infant's findings?

A Abnormal Wiskott-Aldrich syndrome protein

B 22q- chromosome deletion

C Reduction in CD4 lymphocytes

D Defect in NADPH oxidase

E Failure of B cell maturation into plasma cells

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Question 43

A 46-year-old woman has experienced progressive, increasing muscular weakness, particularly toward the end of the day, over the past 2 months. She does not have arthralgias or myalgias. On physical examination her motor strength goes from 5/5 to 4/5 with repetitive movement of extremities. A chest CT scan reveals an anterior mediastinal mass. Laboratory studies show that her antinuclear antibody test is negative. By which of the following immunologic mechanisms is her disease most likely produced?

A Local immune complex formation

B Interleukin release from macrophages

C Binding of anti-receptor antibody

D Mast cell degranulation

E Cross-reactivity with tissue antigens

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Question 44

A 45-year-old woman has noted episodes of pain with swelling and warmth of her hands and feet for the past 3 weeks. During these episodes, lasting hours to days, it is difficult for her to walk or to prepare meals. On physical examination she has painful 1 cm subcutaneous nodules on the extensor surfaces of her elbows. Over the next 6 years, her hands become deformed so that it is difficult to perform tasks as simple as opening a door or buttoning her blouse. Which of the following laboratory test findings is she most likely to have?

A HLA B27

B ANA positive at 1:256

C Elevated rheumatoid factor

D Markedly decreased serum complement

E Hypogammaglobulinemia

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Question 45

A 7-year-old boy has had recurrent upper and lower respiratory tract bacterial infections since infancy. On examination he has eczema and areas of ecchymoses on his skin. Laboratory studies show Hgb 11 g/dL, WBC count 7600/microliter, and platelet count 44,000/microliter. His brother and a paternal uncle are similarly affected. What is the most likely diagnosis?

A Bruton agammaglobulinemia

B Complement deficiency

C DiGeorge syndrome

D Severe combined immunodeficiency

E Wiskott-Aldrich syndrome

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Question 46

A study of persons with inflammatory bowel diseases shows that their course of illnesses extends over decades. During this time there are bowel lesions marked by ulceration of the mucosa. Inflammatory cells are present that participate in a TH17 immune response. Which of the following cell types is mediating the tissue injury in these persons?

A B lymphocytes

B Dendritic cells

C NK cells

D Neutrophils

E T lymphocytes

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