Receptor Singling

Question 1

An antigen binding signal at the membrane results in the mature B lymphocyte changing its
a. antigen-binding specificity.
b. color.
c. Ig V-D-J gene rearrangement.
d. gene expression.
e. signal transduction molecules.

Answer 1

d. gene expression.

Question 2

Signal transduction is the process of converting
a. a B cell to a T cell.
b. a binding signal to a chemical signal.
c. a hapten to an antigen.
d. IgA to secretory IgA.
e. a kinase to a phosphatase.

Answer 2

b. a binding signal to a chemical signal.

Question 3

A ligand is
a. a cytokine.
b. a molecule that specifically binds a receptor.
c. an antigen.
d. an enzyme.
e. all of the above are ligands.

Answer 3

e. all of the above are ligands.

Question 4

A tyrosine kinase which is activated by antigen binding is found in the ________ of the BCr or TCR complex.
a. cytoplasmic domain
b. extracellular domain.
c. Ig superfamily domain.
d. transmembrane domain.
e. variable domain.

Answer 4

a. cytoplasmic domain

Question 5

The ligand for TCR is
a. BCR.
b. MHC
c. MHC + peptide.
d. peptide.
e. TCR ligand.

Answer 5

c. MHC + peptide.

Question 6

An oncogene is a gene that is associated with
a. apoptosis.
b. cancer.
c. ITIMs.
d. TCR and BCR signal transduction.
e. viruses.

Answer 6

b. cancer.

Question 7

Antigen binding to B cells is most effective at sending an activation signal to the B cell if it causes
a. antigen processing and presentation on Class II MHC.
b. BCR clustering.
c. BCR internalization.
d. inflammation.
e. opsonization.

Answer 7

b. BCR clustering.

Question 8

An enzyme which puts a phosphate group on a protein molecule is called a
a. co-receptor.
b. ITAM.
c. kinase.
d. phosphatase.
e. receptor.

Answer 8

c. kinase.

Question 9

Gene expression does NOT necessarily involve
a. changes in a cell’s activities (phenotype).
b. mRNA synthesis.
c. protein synthesis.
d. DNA synthesis.
e. transcription factors.

Answer 9

d. DNA synthesis.

Question 10

The signal transduction molecules associated with TCR are
a. CD1.
b. CD3.
c. CD4.
d. CD8.
e. CD22.

Answer 10

b. CD3.

Question 11

The signal transduction molecules associated with BCR are
a. CD21 and CD81.
b. Iga and Igb
c. IgD and IgM.
d. ITAMs and ITIMs.
e. RAG-1 and RAG-2.

Answer 11

b. Iga and Igb

Question 12

The second messenger IP3 increases the cytoplasmic concentration of
a. antigen.
b. calcium.
c. Class I MHC.
d. phosphate.
e. sodium.

Answer 12

b. calcium.

Question 13

DAG and IP3 are released from PIP2 by the action of
a. adaptor protein.
b. phospholipase C (PLC).
c. protein kinase C (PKC).
d. small G protein.
e. TdT.

Answer 13

b. phospholipase C (PLC).

Question 14

Small G proteins (like Ras) convert GTP to GDP by their ________ activity.
a. GEF.
b. kinase.
c. phosphatase.
d. polymerase.
e. protease.

Answer 14

c. phosphatase.

Question 15

Transcription factors
a. increase synthesis of mRNA.
b. increase synthesis of DNA.
c. inhibit synthesis of mRNA.
d. promote DNA phosphorylation.
e. synthesize mRNA.

Answer 15

a. increase synthesis of mRNA.

Question 16

An enzyme cascade is a
a. case where the enzyme catalyzes its own inactivation, like small G proteins.
b. pair of enzymatic reactions that have opposite effects, like kinases and phosphatases.
c. series of enzymatic reactions that result in cancer.
d. series of enzymatic reactions where the product of one reaction catalyzes the next reaction.
e. small waterfall.

Answer 16

d. series of enzymatic reactions where the product of one reaction catalyzes the next reaction.

Question 17

Signal transduction complex associates with TCR in the membrane through
a. agonist peptides.
b. covalent bonds.
c. enzyme cascades.
d. reverse phosphorylation.
e. salt bridges.

Answer 17

e. salt bridges.

Question 18

If IgaIgb cannot be made, B cells
a. cannot express BCR.
b. cannot express Class II MHC.
c. express 1,000-fold less BCR than usual
d. synthesize CD3 and become T cells.
e. require 1,000-fold more antigen to be activated.

Answer 18

a. cannot express BCR.

Question 19

The immune system of a person who had a mutation in CD3 could NOT fight a viral hepatitis A infection by
a. blocking Hepatitis A virus from infecting liver cells with neutralizing IgG antibodies.
b. generating cytotoxic T cells to lyse infected liver cells
c. lysing virus-infected cells with NK cells.
d. phagocytosing complement-opsonized Hepatitis A virus.
e. Both 1 and 2 are correct.

Answer 19

e. Both 1 and 2 are correct.

Question 20

Amino acid sequences in lymphocyte signal transduction complexes which are phosphorylated following antigen binding are called
a. ITAMs.
b. ITIMs.
c. MAPs.
d. PTKs.
e. syks.

Answer 20

a. ITAMs.

Question 21

An immune deficiency resulting from a defective PTK in the activation cascade in B cells would probably be characterized by
a. high numbers of circulating B cells.
b. high numbers of circulating lymphocytes.
c. high concentrations of plasma immunoglobulins.
d. low concentrations of plasma immunoglobulins.
e. low numbers of circulating T cells.

Answer 21

d. low concentrations of plasma immunoglobulins.

Question 22

B cell co-receptor complex CD19, CD22, and CD81
a. allows B cells to be activated with 1,000-fold less complement-coated antigen.
b. allows B cells to be activated with 1,000-fold more complement-coated antigen.
c. decreases B cell expression of BCR.
d. increases B cell expression of BCR.
e. prevents B cell activation by self antigen.

Answer 22

a. allows B cells to be activated with 1,000-fold less complement-coated antigen.

Question 23

The anti-rejection drugs cyclosporin A and FK506 block rejection of transplanted organs by interfering with
a. activation of a T cell transcription factor required for T cell activation.
b. antibody synthesis required for ADCC of transplanted cells.
c. CD3 expression.
d. MHC Class I expression.
e. processing of graft peptides and presentation on Class I MHC.

Answer 23

a. activation of a T cell transcription factor required for T cell activation.

Question 24

Antagonist peptides
a. fail to bind to T cells.
b. fully activate T cells.
c. interfere with T cell activation by agonist peptides.
d. partially activate T cells.
e. require partial agonist peptides to fully activate T cells.

Answer 24

c. interfere with T cell activation by agonist peptides.

Question 25

Antibody-dependent cell-mediated cytotoxicity (ADCC) is a process in which antibody-coated cells are killed by
a. the antibodies.
b. complement.
c. cytotoxic T cells.
d. cells with Fc receptors for IgG3.
e. cells with Fc receptors for IgE.

Answer 25

d. cells with Fc receptors for IgG3.

Question 26

When IgE on mast cell FceR is cross-linked by, antigen, the mast cell responds by
a. apoptosis.
b. presenting the antigen to Th cells.
c. secreting IgE.
d. secreting histamine and other allergic mediators.
e. stimulating macrophage and neutrophil phagocytosis of the coated antigen.

Answer 26

d. secreting histamine and other allergic mediators.

Question 27

Homeostasis is
a. macrophage activation by bacterial antigens.
b. programmed cell death.
c. the normal process of signal transduction.
d. the synthesis from all leukocytes from bone marrow stem cells.
e. the regulation of biological systems within normal limits.

Answer 27

e. the regulation of biological systems within normal limits.

Question 28

STAT proteins are NOT
a. cytosolic proteins.
b. involved in cytokine signaling.
c. JAK kinases.
d. signal transducers.
e. transcription activators.

Answer 28

c. JAK kinases.

Question 29

Cells receive a death signal through
a. bcl-2 receptor.
b. death receptor.
c. Fas.
d. Fas ligand.
e. STAT ligand.

Answer 29

c. Fas.

Question 30

The most important receptor through which lymphocytes receive life and death signals is
a. antigen receptor.
b. bcl-2 receptor.
c. Fas receptor.
d. FcR.
e. growth factor receptor

Answer 30

a. antigen receptor.