Complement

Question 1

Complement participate in both:

Answer 1

innate and adaptive immune responses

Question 2

Complement is involved in all of the following:

Answer 2

• attraction of neutrophils to an infection site
• increase serum proteins in infected tissues
• lysis of bacteria during the absence of specific antibodies
• opsonization of microorganisms for phagocytosis

Question 3

Complement is present in:

Answer 3

circulation as inactive form

Question 4

The alternative pathway of complement activation:

Answer 4

requires C3

Question 5

If a person is born without C2 and C4 the amount of C3b produced during bacterial infections will be:

Answer 5

reduced

Question 6

Which is least sensitive to complement-mediated lysis?

Answer 6

Gram-positive bacteria

Question 7

In the membrane attack phase of the classical complement pathway, the role of C5b is to:

Answer 7

initiate formation of the MAC

Question 8

Complement receptors on erythrocytes:

Answer 8

remove immune complexes from the circulation

Question 9

As complement is activated by complexes of antibody-coated bacteria, bystander lysis of nearby host cells is prevented by:

Answer 9

proteins on host cell membranes that inhibit MAC formation

Question 10

Complement activity is restricted by:

Answer 10

• dissociation of C3 and C5 convertases
• Gram positive cell walls that are resistant to MAC polymerization
• host cell plasma proteins that inactivate C3a, C4a and C5a activity
• proteolytic cleavage of complement proteins into smaller fragments

Question 11

A deficiency in complement proteins or in their regulators can result in:

Answer 11

• blood in urine from erythrocyte lysis
• decreased levels of certain complement proteins in the circulation
• immune complex disease
• increased infections