Question 1

The B-cell co-receptor is composed of

Accepted Answer

The B-cell co-receptor is composed of three proteins - CR2 (CD21), CD19, and CD81. This complex amplifies B-cell receptor signaling and enhances B-cell activation and survival. Igα, Igβ, Lyn tyrosine kinase, CD14, CD40, MHC class II, and CED19 are all involved in various aspects of B-cell activation, but they are not part of the B-cell co-receptor.

Question 2

How does IgE induce the forcible ejection of parasites and toxic substances from the respiratory and gastrointestinal tracts?

Accepted Answer

The answer of How does IgE induce the forcible ejection...

Question 3

A.Explain how the poly-Ig receptor transports dimeric IgA antibodies across cellular barriers,and specify the type of cell barrier involved.
B.What are the final locations of the transported material?

Accepted Answer

The answer of A.Explain how the poly-Ig receptor transports dimeric...

Question 4

Some types of B-cell tumor have been treated with rituximab,an anti-CD20 monoclonal antibody,which exerts its effect through a mechanism known as ______ involving the participation of NK cells.

Accepted Answer

Antibody-dependent cell-mediated cytotoxicity (ADCC) is the mechanism through which rituximab exerts its effect on B-cell tumors. This involves the binding of rituximab to CD20 on target B-cells, followed by recognition and effector cell-mediated killing of the target cells, mainly through the participation of natural killer (NK) cells.

Question 5

For IgG2 to be effective at stimulating uptake of IgG2-coated bacteria,_____.

Accepted Answer

The H131 allotype of FcγRIIA has a higher affinity for IgG2, which is necessary for effective phagocytosis of IgG2-coated bacteria.

Question 6

A.What are the similarities between the activation of mast cells and NK cells via FcεRI and FcγRIII,respectively? Be specific.
B.What are the differences? Again,be specific.

Accepted Answer

The answer of A.What are the similarities between the activation...

Question 7

Complexes of IgG bound to soluble multivalent antigens can activate the classical pathway of complement,resulting in the deposition of _____ on the complex,targeting it for endocytic uptake by cells bearing _____.

Accepted Answer

The activation of the classical pathway of complement by IgG-bound soluble multivalent antigens results in the deposition of C3b on the complex, which targets it for endocytic uptake by cells bearing CR1 and Fc receptors. Therefore, option D is the correct choice.

Question 8

Which of the following is a characteristic of follicular dendritic cells in the primary follicles of secondary lymphoid tissues? (Select all that apply.)

Accepted Answer

Follicular dendritic cells in the primary follicles of secondary lymphoid tissues provide a stable depository of intact antigens able to bind to B-cell receptors and have a large surface area as a result of forming dendrites. They are not bone marrow derived hematopoietic cells and do not internalize immune complexes through CR2 receptor cross-linking or produce cytokines that induce B cells to proliferate and become centroblasts.

Question 9

A distinguishing feature of FcγRIIB1 compared with FcγRIIA is _____.

Accepted Answer

FcγRIIB1 has ITIMs (immunoreceptor tyrosine-based inhibitory motifs) in its cytoplasmic tails, which leads to its inhibitory function. FcγRIIA, on the other hand, activates cells and induces endocytosis, and does not possess ITIMs. The ability to bind to IgG1 or expression on NK cells are not defining features that distinguish FcγRIIB1 from FcγRIIA.

Question 10

C3 convertase of the classical pathway is _____,whereas C3 convertase of the alternative pathway is _____.

Accepted Answer

The C3 convertase of the alternative pathway is formed by the association of C3b with factor Bb, giving rise to the C3bBb complex. The C3 convertase of the classical pathway is formed by the association of C4b and C2a, giving rise to the C4bC2a complex. Therefore, the correct choice is B.

Question 11

IgM is particularly efficient at fixing complement because it _____.

Accepted Answer

IgM is particularly efficient at fixing complement because it has a pentameric structure, providing five binding sites for the first component of the classical complement pathway, C1q, when it adopts its staple configuration upon antigen binding. This multivalent interaction greatly enhances the efficiency of complement fixation.

Question 12

Explain the origin of the secretory component and its significance after the release of dimeric IgA from the apical face of the gut epithelium.

Accepted Answer

The answer of Explain the origin of the secretory component...

Question 13

Describe the course of events that results in the swollen lymph nodes characteristic of many infections.Use the following terms in your

Accepted Answer

The answer of Describe the course of events that results...

Question 14

A.What is meant by the term "passive transfer of immunity," and how is it achieved? Give examples.
B.Give the isotype of the antibodies involved in (i)placental transfer and (ii)transfer into breast milk,and explain why these antibodies are important.
C.Do you think it is possible for a pregnant mother who has an autoimmune disease to transfer autoreactive antibodies to the developing fetus? Explain your answer.

Accepted Answer

The answer of A.What is meant by the term "passive...

Question 15

A.What is the main effector function of IgM antibody?
B.Why is IgM efficient at (i)preventing blood-borne infections and (ii)fixing complement,but (iii)less efficient than other antibody classes in inducing phagocytosis of immune complexes?

Accepted Answer

The answer of A.What is the main effector function of...

Question 16

Naive B cells search for specific antigen displayed by follicular dendritic cells in primary follicles.Naive T cells,however,search for specific antigen presented by ______.

Accepted Answer

Naive T cells recognize specific antigen presented by dendritic cells, which are specialized antigen-presenting cells that migrate to secondary lymphoid organs to activate T cells. The other cell types listed, such as subcapsular sinus macrophages and tingible body macrophages, may indirectly contribute to antigen presentation or clearance, but they are not the primary cells that activate naive T cells.

Question 17

Which of the following is consistent with a recently antigen-activated mast cell?

Accepted Answer

Mast cells store prepackaged granules containing histamine and other inflammatory mediators. When activated by an antigen, the granules are released rapidly, causing an allergic reaction or inflammation. Therefore, the absence of prepackaged granules is not consistent with a recently activated mast cell. The other choices are not consistent with a recently antigen-activated mast cell either.

Question 18

From an immunological viewpoint,why would it be inadvisable for a mother who has recently given birth to move with her newborn to a foreign country where there are endemic diseases not prevalent in her homeland?

Accepted Answer

The answer of From an immunological viewpoint,why would it be...

Question 19

The γ chain of the FcγRI receptor is closely related to the _____,which contains _____.

Accepted Answer

The answer of The γ chain of the FcγRI receptor...

Question 20

The process involving receptor-mediated transport of macromolecules from one side of a cell to the other is called

Accepted Answer

The answer of The process involving receptor-mediated transport of macromolecules...

Quiz 9: Immunity Mediated by B Cells and Antibodies

The B-cell co-receptor is composed of

How does IgE induce the forcible ejection of parasites and toxic substances from the respiratory and gastrointestinal tracts?

A.Explain how the poly-Ig receptor transports dimeric IgA antibodies across cellular barriers,and specify the type of cell barrier involved. B.What are the final locations of the transported material?

Some types of B-cell tumor have been treated with rituximab,an anti-CD20 monoclonal antibody,which exerts its effect through a mechanism known as ______ involving the participation of NK cells.

For IgG2 to be effective at stimulating uptake of IgG2-coated bacteria,_____.

A.What are the similarities between the activation of mast cells and NK cells via FcεRI and FcγRIII,respectively? Be specific. B.What are the differences? Again,be specific.

Complexes of IgG bound to soluble multivalent antigens can activate the classical pathway of complement,resulting in the deposition of _ on the complex,targeting it for endocytic uptake by cells bearing _.