Deck 22: Immunology

Question 1

Explain why only one in three attempts at somatic recombination results in a productive VJ or VDJ combination.

Answer 1

The final steps in somatic recombination involve ligation of the coded regions.This step is imprecise.Whenever V > J,D > J,or V > DJ elements recombine,the resulting reading frame is random.Only one in three attempts will result in a reading frame that is compatible with either heavy-chain or light-chain synthesis.

Question 2

Describe how the heavy chains and light chains are arranged in IgA or IgG antibody molecules.

Answer 2

IgA and IgG immunoglobulins are each composed of two identical heavy chains covalently attached to two identical light chains.Both the light chains and the heavy chains have variable and constant regions,with the variable regions located at their N-terminal ends.Both the variable and constant regions are folded into compact domains composed exclusively of β sheets.

Question 3

During B-cell development,antibody production switches from membrane-bound IgM to secreted antibody production.How does this switch occur?

Answer 3

Somatic recombination of the immunoglobulin heavy-gene locus first creates a rearranged gene that can express a membrane-bound μ chain.Antigen binding is required before the B cell can switch to secreted antibody production.The choice between membrane-bound versus secreted IgM depends on differential use of polyadenylation sites in the μ transcript.The μ transcript has two potential polyadenylation sites.If the downstream site is chosen,the resulting protein includes a C-terminal membrane anchor,which yields a membrane-bound form of μ .If the upstream polyadenylation site is used,the membrane anchor is bypassed,and the transcript is processed to yield the secreted version of the μ chain.

Question 4

Which of the following would occur from B-cell class switching?

A)rearrangement of the light chain
B)new VDJ recombination that still retains antigen specificity
C)production of IgA secreted into the bloodstream with the same antigen specificity
D)production of IgG γ2 with the same antigen specificity

Question 5

When comparing transcytosis of IgA in tears and IgG in neonates,which of the following is NOT true?

A)Both processes involve transport into and back out of an epithelial cell.
B)Both processes require recognition of the immunoglobulin by a cell surface receptor.
C)Both processes result in cleavage by proteolysis to release the bound immunoglobulin.
D)Both processes rely on vesicle trafficking within a cell.

Question 6

Describe the role of Fc receptor proteins in antibody-dependent cell-mediated cytotoxicity.

Question 7

What roles do natural killer cells play in the innate immune response?

Question 8

Which of the following is NOT an example of a mechanical or chemical barrier to pathogens?

A)lysozymes in tears
B)acids secreted in the stomach
C)phagocytes
D)tight junctions between epithelial cells

Question 9

Treatment of IgG antibodies with the protease pepsin yields:

A)fragments that retain antigen-binding capacity but are monovalent.
B)separated heavy and light chains.
C)single chain antibodies similar to those made by camelids.
D)bivalent fragments called F(ab)s.

Question 10

Which class of immunoglobulins is made first?

A)IgA
B)IgE
C)IgG
D)IgM

Question 11

Which of the following is NOT a heavy chain isotype?

Question 12

Tear fluids and other secretions are rich in:

A)IgA.
B)IgE.
C)IgG.
D)IgM.

Question 13

Somatic recombination is catalyzed by RAG1 and RAG2 recombinases.How does the RAG1-RAG2 complex recognize the cleavage site at the exact boundary of the coding and signal sequences in the variable regions of immunoglobulin genes?

Question 14

Where do most of the interactions between the cells and molecules required for the immune response occur?

A)in the bloodstream
B)in endothelial tissues
C)in lymph nodes
D)in the thymus

Question 15

During the early stages of B cell differentiation,heavy chains are complexed with:

A) light chains.
B) light chains.
C)surrogate light chains.
D)none of the above

Question 16

ITAMs are part of:

A)Igα and Igβ
B)heavy chains.
C)light chains.
D)surrogate light chains.

Question 17

Which immunoglobulin is secreted as a pentamer?

A)IgA
B)IgE
C)IgG
D)IgM

Question 18

Fluid and immune system cells can escape from blood vessels to provide nutrients and defensive proteins to tissues.How are the cells and fluid replaced to maintain homeostasis in the bloodstream?

Question 19

Which complement components show chemoattractant activity and help recruit neutrophils to sites of complement activation?

A)C1q
B)C1rC1s complexes
C)C2C4 complexes
D)small fragments released from C3

Question 20

Which cell type is responsible for providing an innate immune response to viruses?

A)macrophages
B)natural killer cells
C)dendritic cells
D)epithelial cells

Question 21

Activated CD4 T cells recognize an antigen-experienced B cell by means of:

A)the class I MHC-peptide complexes displayed by the B cell.
B)the class II MHC-peptide complexes displayed by the B cell.
C)both the class I and class II MHC-peptide complexes displayed by the B cells.
D)none of the above

Question 22

Patients who have received an organ transplant take an immunosuppressant called cyclosporine to:

A)encourage the patient's T cells to recognize the new organ cells as "self".
B)upregulate T-regulatory cells to prevent any immune response against the new organ.
C)prevent clonal expansion through inhibition of IL-2 transcription.
D)inhibit calcineurin which results in less NFAT phosphorylation.

Question 23

Experiments that first identified a role for the MHC gene locus in tissue identification were successful in mice because:

A)mice can yield large litters,and great numbers of offspring were needed for genetic analyses.
B)mice have very small genomes,making it easier to link genetic changes to functional changes.
C)mice with identical genetic backgrounds were able to accept tissue transplants,but other strains of mice rejected the tissue.
D)mice without intact immune systems are routinely used to study the effects of MHC molecules.

Question 24

Some Toll-like receptor proteins recognize and destroy CpG-containing bacterial DNA.How do these receptors differentiate between host DNA and DNA from invading bacteria?

Question 25

Self-antigens in the retina and central nervous system are the beneficiaries of a form of tolerance called:

A)anergy.
B)central tolerance.
C)clonal exhaustion.
D)immune privilege.

Question 26

Patients with an X-linked inherited disease called Hyper IgM (XHIGM)syndrome have a deficiency in CD40 ligand,a protein found on the surface of T lymphocytes.Patients with XHIGM are unable to make the class switch between IgM and either IgA or IgG.From this information,you could conclude that:

A)B-cell production of IgM does not depend on the CD40 ligand.
B)the class switch between IgM and either IgA or IgG requires T cells.
C)the switch between membrane-bound IgM and secreted IgM requires T cells.
D)B-cell production of IgM does not depend on the CD40 ligand,and the class switch between IgM and either IgA or IgG requires T cells.

Question 27

Which cells can activate macrophages and stimulate an inflammatory response through the production of IFNγ?

A)CD4 Th1 T cells
B)CD8 T cells
C)regulatory T cells
D)plasma cells

Question 28

In the thymus,T cells can be deleted only if:

A)the appropriate self-antigen is represented adequately in the thymus as MHC-peptide complexes.
B)the appropriate self-antigen is not present in the thymus as a MHC-complex.
C)the T cell cannot engage self MHC proteins.
D)the appropriate self-antigen is represented adequately in the thymus as MHC-peptide complexes,and
The T cell cannot engage self MHC proteins.

Question 29

Monoclonal antibodies are produced by fusing mouse spleen cells with:

A)primary B cells.
B)immature B cells.
C)HGPRT-deficient myeloma cells.
D)T-cells.

Question 30

Compare the class I and class II pathways of antigen processing and presentation.What kinds of antigens are involved? Which types of T cells recognize the antigen-MHC protein complexes?

Question 31

Class switch recombination generates antibodies with:

A)different light-chain variable regions.
B)different light-chain constant regions.
C)different heavy-chain variable regions.
D)different heavy-chain constant regions.

Question 32

Explain why Bence-Jones proteins are different for different B-cell tumors from different patients but identical when isolated from a single tumor.

Question 33

When tissue damage occurs,what attracts neutrophils to the site of damage?

Question 34

Which of the following peaks earliest in the time course of a viral infection?

A)type I interferons
B)NK cells
C)virus-specific CTLs
D)antibody titers

Question 35

_____ sense the presence of cytoplasmic pathogen-derived nucleic acids.

A)Inflammasomes
B)Antigen-presenting cells
C)Toll-like receptors
D)High-affinity antibodies

Question 36

Which of the following is NOT a way that MHC proteins play a role in the immune response?

A)presentation of antigen by class II MHCs on T-cells
B)restrict cytotoxic T-cell killing of virally-infected cells
C)allow lymphocytes to distinguish between "self" and "non-self"
D)presentation of antigen by class II MHCs on B-cells

Question 37

Autoimmune diseases are associated with particular alleles of genes for:

A)cytokines.
B)immunoglobulins.
C)MHC proteins.
D)T-cell receptors.

Question 38

Which receptor proteins are displayed by dendritic cells and specialize in the recognition of microbial and viral products?

A)Toll-like receptors (TLRs)
B)class I MHC proteins
C)class II MHC proteins
D)T-cell receptor proteins

Question 39

In cells with mutations in either TAP1 or TAP2:

A)ubiquitin conjugation would be disrupted and antigen proteins would not be tagged for destruction.
B)ubiquitin-conjugated proteins would not be destroyed by proteasomal proteolysis.
C)peptides generated by proteasomal proteolysis would not be complexed with class I MHC molecules.
D)class I MHC-antigen complexes would be unable to cross the ER membrane.

Question 40

Irradiation prevents mice from generating their own T cells.When the immune systems of irradiated mice are reconstituted with unfractionated CD4 cells,the recipients show no signs of autoimmune disease.However,if the T cells are depleted of the CD4+CD25+ subset prior to transfer,recipients show multi-organ autoimmunity.This result demonstrates the role of _____ in suppressing autoimmunity.

A)cytotoxic T cells
B)helper T cells
C)regulatory T cells
D)all of the above

Question 41

Why has the live-attenuated polio vaccine been recently discontinued?

Question 42

Cancer cells should be recognized by the immune system and destroyed.Which of the following cell and receptors combinations are often dysregulated in tumors?

A)colon cancer epithelial cells - CTLA-4
B)macrophages - class I MHC
C)Tregs - CD40
D)T cells - PD-1