The Complement System Practice System Flashcards
A 25-year-old accountant suffers a paper cut that leads to a Staphylococcus aureus infection (S. aureus is a Gram-positive bacterium). What complement component acts as an opsonin for S. aureus phagocytosis by neutrophils infiltrating the site where the paper cut occurred?
A) C1q
B) C3b
C) C4a
D) C5b
E) Factor B
B
Which complex makes up the C5 convertase of the lectin and classical pathways of complement activation?
A) C3bBb
B) C3bBbC3b
C) C4bC2a
D) C4bC2aC3b (or C4bC2bC3b; they are the same and one thing)
E) C6C7C8C9
D
A 19-year-old female first-year college student presents with acute onset of severe headache, fever, nausea, and vomiting. A CSF analysis is performed and is significant for the following: leukocytes with predominance of PMNs and the presence of Gram- negative diplococci. A presumptive diagnosis of meningitis due to Neisseria meningitidis, a Gram-negative bacterium is made, and the patient is started on antibiotics. What factor is responsible for stabilizing C3 convertase in one of the innate complement cascades that is protective against this microorganism?
A) C12s2
B) CD59
C) Factor D
D) Factor H
E) Factor I
F) MASP1
G) MASP2
H) Properdin
H
A 2-year-old boy presents to the emergency department with fever, headache, stiff neck, and vomiting. The child has not received any immunizations since birth. On examination, the child presents with altered mental status; HR is 84/min, RR 18/min, BP 110/80 mmHg, with positive Kernig’s and Brudzinski’s signs. A CSF analysis performed is significant for increased opening pressure, turbid CSF, leukocytosis with predominance of PMNs, decreased glucose level, increased protein level, and Gram- negative coccobacilli. A presumptive diagnosis of bacterial meningitis is made and the
child treated with antibiotics. What factor is responsible for stabilizing C3bBb in the complement cascade that protects against this microorganism?
A) C4-binding protein
B) Decay-accelerating factor
C) Factor H
D) Factor I
E) Properdin
E
A 19-year-old female first-year college student presents with acute onset of severe headache, fever, nausea, and vomiting. A CSF analysis is performed and is significant for the following: leukocytes with predominance of PMNs and the presence of Gram- negative diplococci. A presumptive diagnosis of meningitis due to Neisseria meningitidis, a Gram-negative bacterium is made, and the patient is started on antibiotics. It is later revealed that the patient has properdin deficiency. What complement complex is most likely to be affected in this deficiency?
A) C3bBb
B) C4bC2a
C) C4bC2aC3b
D) IgG- C1r2s2 complex
E) MAC
A
When acting alone, how does factor H prevent complement activation and host tissue destruction?
A) Cleaves C3b to yield iC3b
B) Dissociates C1q and C1r2s2
C) Dissociates C3b and Bb
D) Prevents poly-C9 assembly
C
A 3-year-old girl suffers recurrent infections as a result of a deficiency in properdin. What type of infection is most likely to be recurring?
A) Bacteria
B) Fungi
C) Protozoan
D) Viral
E) Worm
A
An 8-year-old boy presents to the emergency department with fever, headache, stiff neck, and vomiting. The patient has a history of recurring bacterial infections and has had streptococcal and meningococcal meningitides in the past. Physical examination: HR is 84/min, RR 18/min, BP 110/80 mmHg, with positive Kernig’s and Brudzinski’s signs. Laboratory investigations: CSF analysis is significant for increased opening pressure, turbid CSF, leukocytosis with predominance of PMNs, decreased glucose level, increased protein level, and Gram-positive streptococci; genetic studies also reveal the boy has C3 deficiency, a rare autosomal-recessive inherited disorder. What complement functions are affected by this rare deficiency? (choose all that apply)
A) Bacterial lysis
B) B lymphocyte activation
C) Clearance of immune complexes
D) Inflammation
E) Opsonization
A, B, C, D, & E
A 25-year-old man presents with fever, chills, shortness of breath, and cough productive of yellow sputum for the last two days. Patient history is significant for recurrent bacterial infections, many of which pneumonias. On physical examination, BP is 110/70 mmHg, HR is 122/min, RR is 18/min, and crackles are heard in the left lower lobe. A chest x-ray is shown below:
The following relevant laboratory investigations are reported: WBC 22,000/mm3, with 70% PMNs and 10% bands. A Gram stain of sputum shows Gram-positive diplococci and culture from the same sample on blood agar yields Streptococcus pneumoniae, a bacterium. Further investigations reveal the patient has CR2 deficiency. Given this diagnosis, which of the following laboratory results would be consistent with this case?
A) High serum concentration of C3
B) High serum concentrations of IgM, IgG, and IgA
C) High serum concentration of mannose-binding lectin D) Low serum concentration of C3
E) Low serum concentrations of IgM, IgG, and IgA
F) Low serum concentration of mannose-binding lectin
E
A 25-year-old man presents with fever, chills, shortness of breath, and cough productive of yellow sputum for the last two days. Patient history is significant for recurrent bacterial infections, many of which pneumonias. On physical examination, BP is 110/70 mmHg, HR is 122/min, RR is 18/min, and crackles are heard in the left lower lobe. A chest x-ray is shown below:
The following relevant laboratory investigations are reported: WBC 22,000/mm3, with 70% PMNs and 10% bands. A Gram stain of sputum shows Gram-positive diplococci and culture from the same sample on blood agar yields Streptococcus pneumoniae, a bacterium. Further investigations reveal low concentrations of IgM, IgG, and IgA as a result of a genetic deficiency. Given the data presented above, which of the following deficiencies is most likely the cause of this man’s recurrent infections?
A) C1q
B) C2
C) CR2
D) Mannose-binding lectin (MBL)
E) Properdin
C
A 35-year-old woman presents with pain and swelling in her wrists, fingers and ankles. Significant findings on physical examination: a red rash is seen on her cheeks and forehead (which the physician discovers after inquiry, worsens after a few hours of sun exposure). The articulations of her hands, wrists, and ankles are swollen and tender. Other physical examination findings are unremarkable. Laboratory investigations further reveal the presence of autoantibodies against nuclear antigen, as demonstrated by a positive serum antinuclear antibody (ANA) test, thereby confirming systemic lupus erythematosus. A component of this disease involves the deposition of immune complexes in different tissues. What complement component is involved in immune complex formation?
A) C2
B) C3
C) Factor B
D) Mannan-binding lectin serine proteases (MASPs)
E) Properdin
B
A 13-year-old boy presents to his physician accompanied by his mother with swelling of the limbs and face, and severe abdominal pain, nausea and vomiting, of 2- days days duration. Patient history is significant for a recent root canal procedure, similar episodes in the past as well as asthma-like attacks, all with increasing severity. Relevant laboratory results: low concentration of serum C1 inhibitor (C1 INH), and depleted concentration of serum C4. The boy is treated with a C1 INH concentrate to relieve the attack. C1 INH is an inhibitor shared by the classical complement pathway and the pathway responsible for this boy’s condition. What is this pathway?
A) Alternative complement pathway
B) Extrinsic pathway
C) Intrinsic pathway
D) Lectin complement pathway
E) Kinin-kallikrein system (Contact activation pathway)
E
An 8-year-old boy presents with his mother to his physician with ulcers in the buccal mucosa and skin around the mouth. Patient history is significant for recurrent bacterial and fungal infections, primarily to skin and mucosa, as well as delayed separation of the umbilical cord. Laboratory investigations reveal that the boy has a CR3 deficiency preventing PMN infiltration to sites of infection. What is the most likely diagnosis?
A) C3 deficiency
B) CD59 deficiency
C) Factor H deficiency
D) Immune-complex disease
E) Leukocyte adhesion deficiency
E
Following complement activation, mast cells release histamine and other inflammatory mediators. What complement fragment triggers mast cell release of these inflammatory mediators?
A) C1q
B) C2a (or C2b, depending on the nomenclature used) C) C3a
D) Factor B
E) Mannose-binding lectin
C
Which of the following is a feature shared by complement proteins?
A) Are heat stable
B) Are opsonins
C) Are primarily synthesized by phagocytic cells
D) Are the same size
E) Are zymogens
E
