Question 1

For each of the following descriptions in questions ,select the Fc receptor (A-G)that best matches it.
Low-affinity Ig receptor on natural killer cells that mediates antibody-dependent cell-mediated cytotoxicity

A)FcgRI (CD64)
B)FcgRIIB (CD32)
C)FcgRIIIA (CD16)
D)FceRI
E)FceRII (CD23)
F)FcaR (CD89)
G)FcRn

FcgRIIIA (CD16)

Accepted Answer

FcF1F1F1S1F1F1F10RIIIA (CD16)is a low-affinity IgG receptor that targets natural killer (NK)cells to bind and destroy IgG-opsonized target cells and signals the NK cell to release cytotoxic granules.

Question 2

For each of the following descriptions in questions ,select the Fc receptor (A-G)that best matches it.
Low-affinity Ig receptor on natural killer cells that mediates antibody-dependent cell-mediated cytotoxicity

A)FcgRI (CD64)
B)FcgRIIB (CD32)
C)FcgRIIIA (CD16)
D)FceRI
E)FceRII (CD23)
F)FcaR (CD89)
G)FcRn

FcgRIIIA (CD16)

Accepted Answer

FcF1F1F1S1F1F1F10RI is a high affinity IgE receptor expressed on mast cells and basophils.Although serum IgE levels are relatively very low,FcF1F1F1S1F1F1F10R1 receptors are fully occupied by IgE due to the high affinity of the receptor.Cross-linking of this receptor by allergen binding to the IgE leads to mast cell activation,which includes granule exocytosis with release of mediators such as histamine,as well as production of lipid mediators and cytokines.

Question 3

For each of the following descriptions in questions ,select the Fc receptor (A-G)that best matches it.
Low-affinity Ig receptor on natural killer cells that mediates antibody-dependent cell-mediated cytotoxicity

A)FcgRI (CD64)
B)FcgRIIB (CD32)
C)FcgRIIIA (CD16)
D)FceRI
E)FceRII (CD23)
F)FcaR (CD89)
G)FcRn

FcgRIIIA (CD16)

Accepted Answer

FcF1F1F1S1F1F1F10RI (CD64)is a high-affinity IgG1 and IgG3 receptor that mediates phagocytosis of opsonized organisms and delivers signals that enhance microbicidal activity of the phagocytes.

Question 4

For each of the functions described in questions ,select the complement system protein (A-F)that best matches it.
Generated by factor I-mediated proteolysis,this complement fragment binds to complement receptor 2 (CR2)on B cells and enhances B cell activation.

A)C3b
B)iC3b
C)C3d
D)C5b
E)C5a

Accepted Answer

C3d is covalently bound to cell surface and is produced by sequential factor I-mediated proteolytic processing of C3.It binds to CR2 on B cells simultaneously with antigen binding to membrane Ig.CR2 is part of a coreceptor complex,which also includes CD19 and CD21.CD19 transduces signals that synergize with the B cell receptor complex signals to activate the B cell.

Question 5

For each of the functions described in questions ,select the complement system protein (A-F)that best matches it.
Generated by factor I-mediated proteolysis,this opsonizing complement fragment binds to CR3 on phagocytes.

A)C3b
B)iC3b
C)C3d
D)C5b
E)C5a

Accepted Answer

C3b is the larger fragment of C3 convertase-mediated cleavage of C3,which becomes covalently bound to cell surfaces and is recognized by complement receptor 1 (CR1)on phagocytes.

Question 6

Which of the following anatomic regions is normally protected from pathogens only by humoral immune responses and not by cell-mediated immune responses?&#10;A)Skin&#10;B)Intestinal lumen&#10;C)Intestinal epithelium&#10;D)Central nervous system&#10;E)Spleen&#10;

Accepted Answer

The lumen of mucosal lined tissues,such as the intestinal and bronchial lumen,are protected by IgA,which is actively secreted at these sites.T cells do not normally migrate into these lumen and are usually involved in immune responses to organisms that breach the surface linings of these structures.The epithelial linings of mucosal tissues and the skin do contain lymphocytes that protect against invading pathogens.Both antibodies and T cells are involved in responses to infections within most other tissues.

Question 7

For each of the following descriptions in questions ,select the Fc receptor (A-G)that best matches it.
High-affinity Ig receptor on mast cells important in immediate hypersensitivity reactions

A)FcgRI (CD64)
B)FcgRIIB (CD32)
C)FcgRIIIA (CD16)
D)FceRI
E)FceRII (CD23)
F)FcaR (CD89)
G)FcRn

Accepted Answer

FcF1F1F1S1F1F1F10RIIB (CD32)is a low-affinity IgG receptor expressed on B lymphocytes.When antigen-IgG complexes simultaneously bind to membrane Ig and to FcF1F1F1S1F1F1F10RIIB,phosphatases activated by FcF1F1F1S1F1F1F10RIIB block activating signals from the B cell antigen receptor complex.

Question 8

For each of the functions described in questions ,select the complement system protein (A-F)that best matches it.
Produced by C3 convertases,this opsonin promotes phagocytosis of microbes.

A)C3b
B)iC3b
C)C3d
D)C5b
E)C5a

Accepted Answer

C5a is a small soluble fragment generated by C5 convertase-mediated cleavage of C5.C5a binds to a G protein-coupled serpentine receptor on neutrophils and stimulates chemokinesis.The C5a receptor is also expressed on other cell types,and C5a has several proinflammatory functions,including mast cell and endothelial cell activation.C3a and C4a have similar biologic activities as C5a,but they are not as potent.Together,C5a,C4a,and C3a are called anaphylatoxins.

Question 9

For each of the functions described in questions ,select the complement system protein (A-F)that best matches it.
Generated by factor I-mediated proteolysis,this opsonizing complement fragment binds to CR3 on phagocytes.

A)C3b
B)iC3b
C)C3d
D)C5b
E)C5a

Accepted Answer

C5b is the larger fragment of C5 generated by C5 convertase.It is the initial component in the formation of the membrane attack complex,which includes C5,C6,C7,C8,and several C9s.
Multiple Choice

Question 10

For each of the functions described in questions ,select the complement system protein (A-F)that best matches it.
Generated by factor I-mediated proteolysis,this complement fragment binds to complement receptor 2 (CR2)on B cells and enhances B cell activation.

A)C3b
B)iC3b
C)C3d
D)C5b
E)C5a

Accepted Answer

iC3b is covalently bound to cell surfaces and is produced by sequential factor I-mediated proteolytic processing of C3.iC3b binds to CR3 and CR4,which are integrins expressed by phagocytes.

Deck 17: Antibody-Immunity