QUESTION 46
A 1-year-old child has had recurrent skin infections. Laboratory testing has revealed elevated white blood cell counts. Molecular testing revealed a defect in the β subunit of CD18 on leukocytes. Of the following, which phase of the neutrophil response during inflammation was most affected?
A. Margination
B. Rolling
C. Adhesion
D. Migration through the endothelium
E. Chemotaxis
Answer for Question 46
Answer: C (adhesion).
Explanation: the child has leukocyte adhesion deficiency, the most common form of which is due to an autosomal recessive mutation involving the β sub-unit of CD18. CD18 is a component of integrins (both LFA-1 and MAC-1). LFA-1 is present on neutrophils and plays a role in adhesion. ICAM-1 on the activated endothelium binds to LFA-1 on the neutrophil causing the neutrophil to adhere to the endothelium. Margination occurs because of vasodilation. Rolling is due to the interaction of selectins and sialyl-Lewis X. Migration through the endothelium involves CD31 (PECAM-1) and agents of chemotaxis (i.e., movement of the leukocyte to the site of injury) are C5a, LTB4, and bacterial peptides.
QUESTION 47
A 13-year-old male was diagnosed just shortly after birth with tetralogy of Fallot following auscultation of a murmur. At 4 days of age, laboratory investigation of jerking motions of his lower extremities revealed a calcium concentration of 4.6 mg/dL. Of the following, fluorescence in-situ hybridization (FISH) would most likely reveal a deletion of?
A. 21q11.1
B. 21q11.2
C. 22q11.1
D. 22q11.2
E. Y chromosome
Answer for Question 47
Answer: D (22q11.2)
Explanation: cardiac defects and hypocalcemia along with T cell immunodeficiency and facial abnormalities are consistent with 22q11.2 deletion syndrome. Previous terminology included DiGeorge syndrome, when the main manifestations were the hypocalcemia and the T cell immunodeficiency, and velocardiofacial syndrome, when the main manifestations were facial dysmorphology and congenital cardiac disease. Both were due to deletions at 22q11.2, with the exact location of the deletion determining the subsequent phenotype of the patient.
QUESTION 48
A 13-year-old girl is roller skating with her friends when a dog runs out in front of her, causing her to crash, during which time, she strikes her left elbow hard on the sidewalk. She returns home and tells her mother what she did. Her mother notices that her left elbow has begun to swell. Of the following, which mediator was most responsible for this change?
A. Histamine
B. CD11a/CD18
C. Leukotriene B4
D. Toll-like receptor
E. C3b
Answer for Question 48
Answer: A (histamine)
Explanation: because of the fall and striking her left elbow, this girl has initiated an acute inflammatory response. The first manifestation is usually swelling, which is due to vasodilation of the vasculature and increased membrane permeability through separation of endothelial cells, which allows for fluid to leave the blood vessel and enter the surrounding soft tissue, hence, the swelling. Histamine is an important mediator in causing this change. CD11a/C18 plays a role in attachment of neutrophils to the endothelium; leukotriene B4 is a chemoattractant; Toll-like receptor plays a role in the body’s ability to identify microbes, and C3b is an opsonin, which allows phagocytes to ingest microbes and other foreign substances.
QUESTION 49
A 13-year-old girl has been having a cough and fever for the last four days, and over the last day developed some difficulty breathing. Her parents did not take her to the emergency room, because they knew a cold was going around. In the morning, they found her unresponsive in her bed. An ambulance was called, but she was pronounced dead. An autopsy was performed, and in the left pleural cavity was a thick white-yellow cloudy fluid substance. Microscopic examination of the lungs confirmed a lobar pneumonia. Of the following, which term best described the substance in the left pleural cavity?
A. A serous exudate
B. A purulent exudate
C. A serous transudate
D. A fibrinous transudate
E. A purulent transudate
Answer for Question 49
Answer: B (a purulent exudate)
Explanation: one complication of pneumonia is pleuritis. In this case, the left pleural cavity was filled with pus (i.e., an empyema). Being cloudy, the fluid is filled with cells. A serous fluid is watery and should be clear. An exudate has an increased amount of protein and most often cells; whereas a transudate is mostly just fluid, with a low protein content and essentially no cells. So, fibrinous and transudate should be mutually exclusive as would purulent and transudate, as a purulent fluid is one filled with neutrophils. A serous exudate is also mutually exclusive.
QUESTION 50
A researcher wants to develop a drug that decreases the acute inflammatory response. The hypothesis is that if neutrophils can be prevented from contacting the endothelium that the acute inflammatory response can be blunted, which may help some patients. Of the following, which mediator would be the best target for the drug?
A. CD31
B. LFA-1
C. P-selectin
D. ICAM-1
E. Toll-like receptor
Answer for Question 50
Answer: C (P-selectin)
Explanation: the researcher hopes to block the rolling stage of acute inflammation. In the rolling stage, Sialyl-Lewis-X molecules on the neutrophils bind to E- or P-selectin molecules on the surface of the endothelium causing loose binding of the white blood cells to the capillary wall. LFA-1 (on neutrophils) binds to ICAM-1 on endothelial cells, leading to adhesion. CD31 (PECAM) plays a role in transmigration and Toll-like receptor plays a role in recognition of microbes.
QUESTION 51
Two individuals rescued from a house fire are brought to the emergency room. One sustained a large bruise on the left forearm when a beam collapsed and struck them and the other sustained 9% body surface area burns on their trunk. The bruise swells for a short period of time and then the swelling dissipates; however, the burn continues to weep fluid, requiring frequent dressing changes over the course of two weeks. What did the burn victim sustain that the contused individual did not?
A. Rapid release of histamine
B. Delayed release of serotonin
C. Activation of CD31
D. Bacterial superinfection
E. Endothelial necrosis
Answer for Question 51
Answer: E (endothelial necrosis)
Explanation: both individuals have evidence of increased vascular permeability, with fluid leaking from the vessel into the surrounding tissue. Increased vascular permeability can occur by two mechanisms: endothelial retraction or endothelial damage. Endothelial retraction as mediated by histamine rapidly leads to increased vascular permeability but the effect is short lived, such as occurred in the individual with the bruise. Endothelial damage occurs rapidly, but is long lived, requiring replacement of the damaged endothelium during the repair process. This can occur in burns, or due to the effects of a bacterial, or other microbial infection. While a bacterial superinfection can occur in a burn patient, it is not required to have continued loss of fluid.
QUESTION 52
A pathologist is examining sections from the heart of an individual who sustained an acute myocardial infarct and subsequently died. In the section, the pathologist notes coagulative necrosis and a brisk neutrophilic response, with large aggregates of neutrophils scattered throughout the tissue. No macrophages are identified and all neutrophils appear intact. Of the following, what was the time frame between the occurrence of the infarct and the individual’s death?
A. 5 seconds
B. 15 minutes
C. 3 hours
D. 1 day
E. 1 week
Answer for Question 52
Answer: D (1 day)
Explanation: although an acute inflammatory infiltrate begins immediately after the time of injury, the gross and microscopic changes take some time to develop. As vasodilation and fluid exudation is rapid, red discoloration and swelling can be seen within minutes; however, development of the neutrophilic response described would take a little time. Following the acute inflammatory response, macrophages would move in to clean up the mess. After 5 seconds and 15 minutes, no neutrophils would be expected. While neutrophils may be present at 3 hours, a significant infiltrate on microscopic examination would not be identified; at 1 week, the neutrophilic response should have ended (usually by a few days), the macrophage response should be complete or nearly completed (with macrophages beginning to enter the picture around 2-3 days).
QUESTION 53
A pathologist is examining a section of gallbladder that was resected from a patient having abdominal pain. Of the following, which would indicate the patient had chronic cholecystitis instead of acute cholecystitis?
A. Neutrophilic infiltrate
B. Edema of the wall of the gallbladder
C. Dilated blood vessels
D. New blood vessel formation
Answer for Question 53
Answer: D (new blood vessel formation).
Explanation: the first three answers (neutrophilic infiltration, edema of the tissue, and dilated blood vessels) are found in acute inflammation. New blood vessel formation along with fibrosis, infiltrates of mononuclear cells (e.g., macrophages and lymphocytes), and tissue destruction are features of chronic inflammation.
QUESTION 54
A 52-year-old male is found dead in his house during a welfare check by police. At autopsy, he is found to have an organizing thrombus in the left anterior descending coronary artery and a corresponding infarct of the anterior wall of the left ventricle. Microscopic examination of the infarct reveals some neutrophils, but also a prominent number of macrophages, which have engulfed necrotic debris and degenerating neutrophils. Which of the following mediators activated the macrophages?
A. IL-13
B. IFN-γ
C. Eotaxin
D. TGF-β
E. C5a
Answer for Question 54
Answer: B (IFN-γ)
Explanation: the macrophages present at the infarct would be classically activated macrophages, responsible for removing the dead cells. IFN-γ is a major mediator for activating macrophages through this pathway. IL-13 activates macrophages through the alternative pathway, and macrophages activated via this pathway (M2 macrophages) promote wound repair, including fibrosis and angiogenesis. Eotaxin is chemoattractive for eosinophils and C5a stimulates release of histamine, and is also chemoattractive for neutrophils, monocytes, and basophils. TGF-β is secreted by activated macrophages and promotes fibrosis during wound repair.
QUESTION 55
A pathologist is examining a lung biopsy in a patient suspected of having tuberculosis. Numerous granulomas are identified throughout the biopsy. An acid-fast stain reveals occasional acid-fast bacilli, consistent with tuberculosis. Of the following, what did every granuloma have?
A. Giant cells
B. A fibrous rim
C. A rim of lymphocytes
D. Central necrosis
E. Epithelioid histiocytes
Answer for Question 55
Answer: E (epithelioid histiocytes)
Explanation: a granuloma is composed of epithelioid histiocytes, which are large eosinophilic macrophages [histiocyte is another term for macrophage]. While granulomas can individually possess any of the other features listed (giant cells, a fibrous rim, a rim of lymphocytes, or caseous necrosis), the only feature listed that all granulomas possess is the epithelioid histiocytes.
QUESTION 56
A 19-year-old female presents to an acute care clinic with complaints of fever, chills, and a productive cough that has been lasting for 3 days. An x-ray reveals consolidation of the lower lobe of her left lung. A diagnosis of lobar pneumonia is made. Laboratory testing reveals a white blood cell count of 18,000 cells/mL. Which of the following mediators was most responsible for her clinical presentation?
A. IL-1
B. IL-2
C. IL-3
D. IL-4
E. IL-5
Answer for Question 56
Answer: A (IL-1)
Explanation: IL-1 (also TNF and IL-6) are responsible for producing the acute phase response in patients with acute infections. The acute phase responses include fever, elevated acute phase proteins (e.g., C-reactive protein and fibrinogen), leukocytosis, and also increased heart rate and blood pressure.
QUESTION 57
A 22-year-old male slides into the plate during a league softball game and scrapes his left knee. Penetration through which of the following layers indicates that he is most likely to develop a scar?
A. Stratum corneum
B. Stratum granulosum
C. Stratum spinosum
D. Stratum basale
E. Basement membrane
Answer for Question 57
Answer: E (basement membrane).
Explanation: With the squamous epithelium of the skin having such good regenerative capabilities, injury to the epidermis will result in complete resolution, however, once the injury perforates the basement membrane, complete resolution is no longer possible and a scar will result.