Immuno Set 5 (Complement) Flashcards
An 11-year-old female with suspected SLE was referred to the Immunologic Diseases Center by a dermatologist. She was clinically diagnosed with lupus erythematosus 2 years earlier and was treated with topical tacrolimus and hydrocortisone cream. The physical examination was normal besides her evident skin lesions. Patient’s blood pressure was within the normal range (100/56 mm Hg). Laboratory investigations revealed elevated levels of CRP (42 mg/L) and increased erythrocyte sedimentation rate (ESR, 50 mm/h [normal < 20 mm/hr]). Complement levels of C3 and C5 were normal and C1 was low. No abnormalities in complement regulatory proteins were found. Which of the following reaction is most likely dysregulated in this patient?
A. Lysis of bacteria via the AP B. NK-mediated lysis of tumor cells. C. Generation of ROS and NO D. Lysis of bacteria via the CP E. C3b-mediated phagocytosis of bacteria
D. Lysis of bacteria via the CP
A 7-year-old male presents with a history of recurrent bacterial infections. Initial laboratory investigations revealed elevated levels of CRP and an increased ESR (111 mm/h). No abnormalities were detected on chest radiography, ECG, echocardiography or abdominal ultrasonography. Complement investigation revealed a complete absence of C3. Which complement-mediated function would remain intact in such a patient?
A. lysis of bacteria B. opsonization of bacteria C. generation of anaphylatoxins D. generation of neutrophil chemotactic factors E. None of the above
E. None of the above
A 3-year-old female presents with pyrexia, neck stiffness, and a purpuric rash. Generally patient was lethargic. The past medical history is remarkable meningococcal meningitis at age of 2 from which he made a full recovery after intravenous antibiotic treatment. After performing blood cultures and investigation of complement activity, the patient was diagnosed with meningitis caused by complement deficiency in the CP. Which of the following screening tests would be most useful for confirming the cause of recurrent infections in this patient?
A. quantitation of serum opsonic activity
B. quantitation of serum hemolytic activity
C. quantitation of C3 content of serum
D. quantitation of C1 content of serum
E. electrophoretic analysis of patient’s serum
B. quantitation of serum hemolytic activity
A 27-year-old female presents with airway obstruction caused by laryngeal swelling. The past medical history is remarkable for episodes of recurrent facial swelling that began sometime in childhood. The swelling, which involves the lips, begins suddenly without recognizable precipitating events and lasts for 2 to 3 days. Laboratory investigation revealed a deficiency involving the complement system. Which component of the complement system is deficient in the patient?
A. C1-inhibitor B. C3 convertase C. C5 convertase D. Mannose-binding lectin E. Membrane attack complex
A. C1-inhibitor
A 10-year-old female presents to the Emergency Department with fever and loss of consciousness. Past medical history is remarkable for bacterial meningitis at the age of 8 and pneumonia at the age of 9. The parents were first-degree cousins. Blood cultures grew Streptococcus pneumoniae. Bacterial meningitis was diagnosed and antibiotics were administered. Immunologic investigations performed when the patient had recovered revealed normal immunoglobulin levels. The alternative and lectin pathways of complement activation were normal, but no classical pathway activity was detected. Subsequent genetic analysis revealed a homozygous missense mutation in which of the following complement proteins?
A. C1 B. C2 C. C3 D. C4 E. C5
A. C1
A 59-year-old Russian-speaking male presents with a past medical history significant for diabetes and hypertension presents to the Emergency Department (ED) with two days of fever, headache, and altered mental status. Labs on admission were notable for anemia, thrombocytopenia, hyperbilirubinemia, and coagulopathy. Workup for the cause of patient’s hemolytic anemia revealed a defect in GPI-anchored proteins. Which of the following statements about lesions of the patient’s erythrocytes is not true?
A. The lesions are formed by polymerization of C9 in the membrane.
B. The lesions permit influx of water and ions into the cell.
C. The lesions are structurally similar to those caused by perforin derived from NK cells.
D. Failure to form these lesions in microbial membrane leads to serious infections by extracellular bacteria.
E. The lesions occurs due to a defect in C3 complement component
D. Failure to form these lesions in microbial membrane leads to serious infections by extracellular bacteria.
A 17-year-old male admitted to hospital with the past history of recurrent severe infections caused by extracellular bacteria. Laboratory investigations revealed a deficiency in C3 component of complement. Which of the following may still occur in this patient?
A. Hemolysis B. Angioedema C. Chemotaxis D. Opsonization E. Bacteriolysis
B. Angioedema
A 35-year-old female presents with abdominal distention and pain, along with lower extremity edema, over the past 6 months. Laboratory investigations suggest a deficiency in a soluble complement regulatory protein. Which of the following is defective in this patient?
A. C3bBb B. Decay accelerating factor C. C4bC2aC3b D. Factor I E. CD59
D. Factor I
A 20-year-old trainee at a military training center was admitted to the hospital with fever, nausea, vomiting and headache which started 30 hours before admission. The past medical history is notable for viral meningitis when he was 6 years old. Blood chemistry tests showed an increase in the C-reactive protein, but the other results were within the normal range. When spinal puncture and CSF analysis was carried out, WBC count of 3,850 /mm3 (polymorphonuclear neutrophils 80%, lymphocytes 20%) and red blood cells (RBC) count of 390 /mm3 were found. Clinically, meningococcal sepsis and meningitis due to a deficiency in complement were suspected. Which of the following screening tests would be most useful for confirming a presumptive diagnosis of a congenital absence of a complement component?
A. quantitation of serum opsonic activity
B. quantitation of serum hemolytic activity
C. quantitation of C3 content of serum
D. quantitation of C1 content of serum
E. electrophoretic analysis of patient’s serum
B. quantitation of serum hemolytic activity
A 20-year-old female presents with suddenly developed fatigue, anxiety, and heart palpitations. Laboratory findings are consistent with Systemic Lupus Erythematous (SLE), an autoimmune disease associated with formation of immune complexes (ICs) in the circulation. Genetic investigation revealed a mutation in one of the complement proteins linked to immune complex diseases. Which one of the following represents a molecular mechanism which is most likely abnormal in this patient?
A. C3a solubilizes ICs and attaches to red blood cells
B. C5a solubilizes circulating ICs
C. Factor I releases complement-bound ICs for phagocytosis via Fc receptors
D. Red blood cells capture ICs from blood via Fc receptors
E. C3b attaches ICs to red blood cells via complement receptors for further removal
by phagocytes
E. C3b attaches ICs to red blood cells via complement receptors for further removal
by phagocytes
