Immuno Set 4 (Complement) Flashcards
The C3 and C5 convertases are central to the generation of the inflammatory and opsonic products of complement activation. The C5 convertase cleaves C5 into C5a and C5b fragments. Generation of soluble C5 fragment can lead to many reactions except which of the following?
A. contraction of smooth muscle B. vasodilation C. attraction of leukocytes D. phagocytosis E. All of the above
D. phagocytosis
The alternative pathway of complement activation is characterized by the functions listed below, except: which of the following?
A. use of C3 component B. activation of complement components beyond C3 in the cascade C. participation of properdin D. generation of anaphylatoxin E. use of C1 component
E. use of C1 component
Decay-accelerating factor (DAF) regulates the complement system to prevent complement- mediated lysis of cells and involves in which of the following?
A. dissociation of C4b2a or the C3bBb enzyme complex
B. blocking the binding of C3 convertase to the surface of bacterial cells
C. inhibiting the membrane attack complex from binding to bacterial membranes
D. acting as a cofactor for the cleavage of C3b
E. causing dissociation of C5 convertase
A. dissociation of C4b2a or the C3bBb enzyme complex
Which component(s) of complement could be missing and still leave the remainder of the complement system capable of activation by the alternative pathway?
A. C1, C2, and C3 B. C3 only C. C2, C3, and C4 D. C1, C2, and C4 E. C1, C3, and C4
D. C1, C2, and C4
The most common clinical consequence(s) of C3 deficiency is (are):
A. increased incidence of tumors
B. increased susceptibility to viral infections
C. increased susceptibility to fungal infections
D. increased susceptibility to bacterial infections
E. all of the above
D. increased susceptibility to bacterial infections
A patient presents with recurrent joint pain and renal insufficiency, which is associated with immune complex deposition in these organs. It is determined that the patient does not clear IgG-containing immune complexes from the circulation at a normal rate. A defect in which of the following complement receptors would most contribute to this latter finding?
A. CR1 B. CR2 C. CR3 D. CR4 E. CR5
A. CR1
Mary is a 2-year-old child with a history of recurrent upper respiratory tract infections. She has normal serum Ig levels for her age, and her complete blood count (CBC) and tests for neutrophil functions are normal. The total complement activity of her serum is normal in terms of supporting the lysis of antibody-coated erythrocytes. However, her serum complement is not activated by bacterial lipopolysaccharide (LPS). Which of the following primary deficiencies of the complement system would be most consistent with these findings?
A. C2 deficiency B. Factor D deficiency C. MBL deficiency D. C1-INH deficiency E. DAF deficiency
B. Factor D deficiency
A pediatric patient presents with recurrent staphylococcal infections (pneumonias, sinusitis, and otitis media). Because many of her immune parameters are normal, you hypothesize that she has a defect in her complement system. For which of the following complement components or receptors would a deficiency produce this pattern of recurrent infections?
A. C2 B. C6 C. C8 D. CR1 E. CD59
A. C2
A patient with the immune complex autoimmune disease systemic lupus erythematosus (SLE) is experiencing significant symptoms, including a worsening of her skin rash and evidence of impaired renal function. Which of the following would be most consistent with a worsening clinical course?
A. A decline in C9 levels B. A decline in C3 and C4 levels C. An increase in Factor P levels D. An increase in C1-INH levels E. A decline in C7 levels
B. A decline in C3 and C4 levels
Which of the following is NOT a property of the classical pathway C3 convertase?
A. Compose of proteolytic fragments of C4 and C2
B. Has protease activity specific for C3 to form C3b
C. Inhibited by decay acceleration factor (DAF)
D. Stabilized by C4 binding protein (C4BP)
E. Same substrate specificity as the alternative pathway C3 convertase
D. Stabilized by C4 binding protein (C4BP)
Which of the following statement about C3 is NOT correct?
A. C3 contains an internal thioester bond that participates in covalent linkage to cell surface
B. C3 is the most abundant complement protein in the serum
C. A proteolytic fragment of C3 is a part of both C3 and C5 convertases
D. Activated C3 is a serine protease that cleaves C4
E. C3 in the plasma is spontaneously cleaved into C3b
D. Activated C3 is a serine protease that cleaves C4
- Which of the following events initiates activation of the alternative pathway of complement activation?
A. C1q binding to a microbial surface
B. Mannose-binding lectin binding to a microbial surface
C. Complement receptor 1 (CR1) binding to C3b
D. Factor I cleavage of C3
E. Spontaneous cleavage of C3 to C3b
E. Spontaneous cleavage of C3 to C3b
