Complement Flashcards
Complement
a. is a group of active proteolytic enzymes found in serum.
b. is secreted by macrophages and hepatocytes in response to antigen binding.
c. participates in both innate and adaptive immune responses.
d. prevents lysis of virus-infected cells.
e. All of the above statements about complement are true.
c. participates in both innate and adaptive immune responses
Complement is involved in all of the following except
a. attraction of neutrophils to an infection site.
b. increased presence of serum proteins in the infected tissues.
c. lysis of bacteria in the absence of specific antibodies.
d. opsonization of microorganisms for phagocytosis.
e. sensitization of T cells to antigen
e. sensitization of T cells to antigen
Complement is
a. activated by binding to specific complement receptors.
b. antigen-specific.
c. a potent promoter of virus entry into host cells.
d. a series of intracellular proteins which work with antibody to eliminate endogenous antigen.
e. present in the circulation in an inactive form.
e. present in the circulation in an inactive form.
The alternative pathway of complement activation
a. causes tissue damage in the absence of C1INH.
b. occurs after the classic pathway is activated.
c. occurs only if the classical pathway is ineffective in pathogen clearance.
d. requires C3.
e. requires C4.
d. requires C3.
If a person is born without C2 and C4,
a. C5 can still be cleaved by the classical pathway.
b. C3b will not be able to bind to bacteria.
c. C9 will polymerize inappropriately and lyse host cells.
d. the classical pathway will be changed into the alternative pathway.
e. the amount of C3b produced during bacterial infections will be reduced.
e. the amount of C3b produced during bacterial infections will be reduced.
Which of the following are least sensitive to complement-mediated lysis?
a. Enveloped viruses
b. Erythrocytes
c. Gram negative bacteria
d. Gram positive bacteria
e. Leukocytes
d. Gram positive bacteria
In the membrane attack phase of the classical complement pathway, the role of C5b is to
a. activate the C5 convertase activity.
b. attract neutrophils to lyse the pathogen.
c. initiate formation of the MAC.
d. polymerize into a membrane-spanning channel.
e. All of these are activities of C5b.
c. initiate formation of the MAC.
Complement receptors (CR)
a. activate complement on the surface of pathogens.
b. bind only activated complement proteins.
c. inhibit complement activation on the surface of host cells.
d. on erythrocytes remove immune complexes from the circulation.
e. on macrophages signal host cells to make opsonins.
d. on erythrocytes remove immune complexes from the circulation.
As complement is activated by complexes of antibody-coated bacteria, bystander lysis of nearby host cells is prevented by
a. a long-lived thioester bond on active complement proteins.
b. covalent attachment of all active complement proteins to the pathogen surface.
c. plasma proteins that inactivate the anaphylatoxins.
d. proteins on host cell membranes that inhibit MAC formation.
e. the slow catalytic rates of complement proteases.
d. proteins on host cell membranes that inhibit MAC formation.
Complement activity is restricted by all of the following EXCEPT
a. dissociation of C3 and C5 convertases.
b. Gram positive cell walls that are resistant to MAC polymerization.
c. host cell plasma proteins that inactivate C3a, C4a, and C5a activity.
d. LPS in the outer membrane of Gram negative bacteria that inactivates C3b.
e. proteolytic cleavage of complement proteins into smaller fragments.
d. LPS in the outer membrane of Gram negative bacteria that inactivates C3b.
A deficiency in complement proteins or in their regulators can result in
a. blood in the urine from erythrocyte lysis.
b. decreased levels of certain complement proteins in the circulation.
c. immune complex disease.
d. increased numbers of infections.
e. All of the above can result from complement deficiencies.
e. All of the above can result from complement deficiencies.
