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CHaPtEr 21 The Human Complement System: Basic Concepts and Clinical Relevance 317.e1

MUL t IPLE-CH o ICE QUES t I o NS

1. All of the following are features of the complement system C. Reduced C4 and C3 correlate with renal disease, DNA
EXCEPT for: antibodies, and, overall, more severe disease.
A. It works in a few minutes and features a feedback loop. D. A rise in C4 and C3 to normal levels with immunosup-
B. It can interact (bind to) almost any foreign material or pressive therapy is associated with a patient having better
self-debris. short-term and long-term clinical outcomes.
C. It is abundant in plasma but also is secreted locally by 4. Which statement is FALSE about complement regulators/
many cells. inhibitors?
D. It has a specific memory system for prior interactions with A. Abundant in plasma.
microbes.
B. Expressed ubiquitously on cell membranes.
2. All of the following are true about a complete deficiency of C. Haploinsufficiency of factor H or factor I is well tolerated
a complement component in the activating cascade EXCEPT: and does not lead to human disease.
A. A deficiency of C5, C6, C7, C8, or C9 usually presents D. A complete deficiency of plasma protein factor H (FH)
with a neisserial infection. or plasma enzyme factor I (FI) leads to overactivation of
B. A deficiency of properdin whose gene is on the X chromo- the alternative pathway (AP) and consumption of C3
some also presents in males with a neisserial infection. (clinical presentation like that of C3 deficiency).
C. A complete deficiency of C3 commonly presents with early
age onset of recurrent viral, fungal, and/or protozoan 5. Which statement is FALSE about complement receptors:
infections. A. Complement receptors are abundant on neutrophils,
D. In the classical pathway (CP), up to C3 (C1q, C4, C2), monocytes, and B lymphocytes.
recurrent bacterial infections and, particularly, autoim- B. Complement system does not participate in adaptive
munity (systemic lupus erythematosus [SLE]) are the two immunity other than by serving as a “complement” to
most common clinical scenarios. immunoglobulin M (IgM)– and IgG-mediated events.
C. Complement receptor one (CR1, CD35) is present on red
3. Which of the following is FALSE relative to measuring C4 blood cells, where it carries out immune adherence for
and C3 antigenic levels in patients with SLE? C4b/C3b–coated materials and then takes them to the
A. A low factor B antigenic level is commonly observed and spleen and/or the liver for transfer to macrophages.
is indicative of alternative pathway (AP) activation. D. Complement receptors and Fcγ receptors work together
B. Low C4 and C3 point to activation of the CP by immune to mediate opsonization and ingestion of infectious bacteria
complexes. and viruses.