immunology quiz #4

25)Which of the following is recognized by cytotoxic T cells?

Cells that display foreign peptides on MHC class I

Which of the following antigenic structures might activate B cell antibody production without the aid of T cells? A. Lysozyme B. Benzene C. Glucose-6-phosphate D. ABO blood group antigen E. Rh factor antigen

D. ABO blood group antigen

Differentiation of TH2 cells from naive precursor cells is dependent on which of the following? A. Toll-like receptor (TLR) ligands B. T-bet C. Interleukin-12 D. GATA-3 E. Interferon-α

D. GATA-3

5)T-independent antigens do NOT

Get presented by MHC class II

8)Which of the following molecules is secreted by Th2 cells after they recognize MHC+Ag and are activated?

IL-4

1)Germinal centers are

sites of rapid antigen-induced B cell division in the lymph nodes & Spleen

14)Cytotoxic T cells produce _________, which induce(s) caspases activation

granzymes

27)Which of the following statements regarding B cells is NOT true?

Activation of B cells requires class I MHC

18)Helper T cells stimulate

B cells to become plasma cells

Which of the following mechanisms contributes to the change from B cell production of membrane Ig to secreted Ig? A. V(D)J recombinase-mediated deletion of the exon encoding the transmembrane domain B. Alternative processing of primary RNA transcripts to remove the transmembrane domain and include a secretory tail piece C. Increased vesicular exocytosis of intracellular stores of the secretory form of Ig D. Switch recombinase-mediated recombination of the heavy chain locus to juxtapose the V(D)J segment with the exon encoding a secretory tail piece E. Up-regulation of ectoenzymes that proteolytically cleave membrane Ig heavy chains just proximal to the membrane

B. Alternative processing of primary RNA transcripts to remove the transmembrane domain and include a secretory tail piece

Which one of the following molecules is important for the production of IgE antibodies? A. CD28 B. CD40 C. IFN-γ D. IL-2 E. TGF-β

B. CD40

20) T cells that activate macrophages, activate what & have what characteristics

-activate macrophages at the site of infection. -activate only macrophages that present specific antigen on MHC class II. -have CD4 expressed on their membranes. -become activated effector cells in response to MHC+antigen plus co-stimulation

The basic immunoglobulin structure consist of

2 identical heavy chains and 2 identical light chains

A 5-year-old boy has a history of recurrent pneumococcal pneumonia, Pneumocystis carinii pneumonia (PCP), and bacterial ear infections. His maternal uncle and an older brother experienced the same symptoms, but he has an older sister who is healthy. Laboratory studies indicate normal numbers of B cells and T cells, and the serum contains mostly IgM and very little IgG. If this patient did have a sister affected with the same condition, which of the following genes would most likely contain a mutation? A. AID (activation-induced deaminase) B. CD40 C. CD40L D. CD28 E. CTLA-4

B. CD40

. Which of the following statements about cell-mediated immunity (CMI) is NOT true? A. Deficiencies in CMI result in susceptibility to infections by viruses and intracellular bacteria. B. CMI can be adoptively transferred by injecting serum from one individual to another. C. Delayed-type hypersensitivity (DTH) is not a protective response against intracellular bacteria such as Mycobacterium tuberculosis. D. The principal form of CMI that protects against viral infections is mediated by CD8+ cytolytic T lymphocytes. E. Phagocytes are essential in the effector phase of CMI responses to bacteria such as Listeria monocytogenes.

B. CMI can be adoptively transferred by injecting serum from one individual to another.

Which one of the following statements about MHC-TCR interactions is NOT true? A. Antigen receptors on T cells bind to MHC molecules for only brief periods of time. B. The affinity of most TCRs for peptide-MHC complexes is similar to the affinity of antibodies for their antigens. C. Only 1% or less of the MHC molecules on any antigen-presenting cell (APC) display a peptide recognized by a particular T cell. D. T cells usually require multiple engagements with an APC before a threshold of activation is reached. E. A subthreshold number of MHC-TCR interactions can lead to T cell inactivation.

B. The affinity of most TCRs for peptide-MHC complexes is similar to the affinity of antibodies for their antigens.

19)Th1 cells will help macrophages eliminate which of the following?

Bacteria that resist lysosomal degradation

11) An immunoglobulin Fab fragment

Bind antigens

6) An immunoglobulin Fab fragment

Binds antigens

A 5-year-old boy has a history of recurrent pneumococcal pneumonia, Pneumocystis carinii pneumonia (PCP), and bacterial ear infections. His maternal uncle and an older brother experienced the same symptoms, but he has an older sister who is healthy. Laboratory studies indicate normal numbers of B cells and T cells, and the serum contains mostly IgM and very little IgG. Which of the following genes most likely contains a mutation in this patient? A. AID (activation-induced deaminase) B. CD40 C. CD40L D. CD28 E. CTLA-4

C. CD40L

Which of the following mechanisms does NOT contribute to the generation of a cytolytic T lymphocyte (CTL) response to a viral infection? A. Dendritic cells phagocytose infected cells or viral particles and present them to naive CD8+ T cells via the class I MHC pathway. B. Dendritic cells are infected with the virus and present viral peptides to naive CD8+ T cells via the class I MHC pathway. C. CTLs are directly activated by CD40L expressed on activated helper T cells through CD40. D. Helper T cells secrete cytokines, such as interleukin-2, that promote the proliferation and differentiation of CD8+ T cells. E. Helper T cells activate infected antigen-presenting cells (APCs) via the CD40 ligand-CD40 pathway, and the activated APCs present viral peptides to naive CD8+ T cells via the class I MHC pathway.

C. CTLs are directly activated by CD40L expressed on activated helper T cells through CD40.

The induction phase of a cell-mediated immune response includes which of the following events? A. CD4+ T cell secretion of interferon-γ leading to macrophage activation B. CD8+ T cell lysis of a virally infected cell C. Clonal expansion of CD8+ T cells within a lymph node D. Migration of CD4+ effector T cells from blood vessels into a tissue site of infection E. Migration of a naive CD4+ T cell from the thymic medulla into the circulation

C. Clonal expansion of CD8+ T cells within a lymph node

All of the following are early T cell events that occur after antigen recognition by the TCR EXCEPT: A. Formation of the immunologic synapse B. Recruitment of signaling molecules, such as LAT, to glycolipid-enriched domains known as lipid rafts C. Enhanced adhesion between T cells and antigen-presenting cells (APCs) via T cell integrin LFA-1 and its ligand on the APC, ICAM-1, at the central zone of the immunologic synapse D. Clustering of the TCR and coreceptors leading to phosphorylation of ITAMs on CD3 by Lck E. Binding of CD28 with costimulators on APCs in the cSMAC, resulting in signal transduction activation

C. Enhanced adhesion between T cells and antigen-presenting cells (APCs) via T cell integrin LFA-1 and its ligand on the APC, ICAM-1, at the central zone of the immunologic synapse

Which one of the following statements about T cells involved in an immune response is NOT true? A. Activated T cells receive survival signals from antigen during an infection. B. Activated T cells contribute to the activation of antigen-presenting cells via CD40 ligand. C. Memory T cells generated during a primary immune response express high levels of interleukin-2 receptors and actively proliferate long after the primary response is completed. D. The major effector function of helper T cells is to activate macrophages and other cells by releasing cytokines. E. When an infection is eliminated, activated T cells die by apoptosis.

C. Memory T cells generated during a primary immune response express high levels of interleukin-2 receptors and actively proliferate long after the primary response is completed.

Which one of the following statements accurately describes antigen recognition events in a lymph node during a helper T cell-dependent antibody response to a protein antigen? A. Naive B cells and naive T cells simultaneously recognize the intact protein antigen. B. Naive B cells recognize intact proteins, generate peptide fragments of these proteins, and present them in complexes with major histocompatibility complex (MHC) molecules to naive helper T cells. C. Naive B cells recognize intact proteins, generate peptide fragments of these proteins, and present them in complexes with MHC molecules to differentiated helper T cells. D. Naive T cells recognize peptides bound to MHC molecules presented by dendritic cells, and naive B cells recognize the intact protein antigen bound to the surface of follicular dendritic cells. E. Differentiated helper T cells recognize peptides bound to MHC molecules on dendritic cells, and the T cells secrete cytokines that promote antibody production by any nearby B cells that have recognized different protein antigens.

C. Naive B cells recognize intact proteins, generate peptide fragments of these proteins, and present them in complexes with MHC molecules to differentiated helper T cells.

An experiment is performed in which a point mutation is introduced randomly into the Zap-70 gene for a particular strain of mice. The mutant mice display a defect in T cell development. However, precursor T cells isolated from the thymus of these mice show normal expression levels of Zap-70 of the correct molecular weight. On further in vitro analysis, the mutant Zap-70 is found to bind to ITAM motifs in the cytoplasmic tail of the ζ chain, but only when the ζ chain is phosphorylated. No phosphorylated LAT is detected, however. Given these data, in which of the following protein domains is the mutation most likely to be present? A. Pleckstrin homology (PH) domain B. Proline-rich (PR) domain C. SH1 domain D. SH2 domain E. SH3 domain

C. SH1 domain

2)B7 on an antigen presenting cell binds to which of theses T- cell ligands?

CD28

15) Which of the following molecules is expressed on Th1 cells' plasma membranes after they recognize HMC+Ag displayed by macrophages?

CD40L

10) which of the following is recognized by helper T cells?

Cells that display foreign peptides on MHC class II

12) Which of the following is produced and displayed by an infected cell to induce a cytotoxic T cell response?

Class I MHC + microbial peptide

In patients with hyper IgM syndrome, there is a genetically based deficiency in expression of CD40 ligand. In addition to defects in antibody isotype switching, these patients have defects in T cell-mediated immune responses and become infected with intracellular parasites. Which one of the following normal functions of CD40 ligand is important in T cell-mediated immunity? A. CD40-dependent isotype switching is required to produce antibody isotypes that activate T cells. B. CD40 ligand is required for CTL killing of CD40-expressing infected cells. C. CD40 ligand is required for maturation of CD4+ T cells in the thymus. D. CD40 ligand on activated T cells binds to CD40 on antigen-presenting cells (APCs), and this enhances the expression of B7-1, B7-2, and cytokines by the APCs. E. CD40 ligand on T cells binds to B7-1 and B7-2 on APCs, and this enhances the function of the APCs.

D. CD40 ligand on activated T cells binds to CD40 on antigen-presenting cells (APCs), and this enhances the expression of B7-1, B7-2, and cytokines by the APCs.

The initial cellular events that are induced by antigen-mediated cross-linking of the B cell receptor (BCR) complex include all of the following EXCEPT: A. Increased percentage of time spent in mitosis, resulting in rapid proliferation B. Increased expression of B7, resulting in enhanced APC function C. Increased expression of bcl-2, resulting in improved survival D. Increased expression of CCR7, promoting migration into lymph node follicles E. Increased expression of the interleukin-2 receptor, resulting in enhanced proliferation and response to T cell signals

D. Increased expression of CCR7, promoting migration into lymph node follicles

Which one of the following descriptions of cytokine interleukin-2 is NOT true? A. Expression of its gene requires multiple transcription factors, such as Fos, Jun, and NFAT. B. It acts as an autocrine growth factor for T cells. C. It binds to CD25 on the cell membrane of T cells. D. It is only involved in the proliferation of helper T cells and not CTLs. E. It promotes susceptibility of T cells to apoptosis.

D. It is only involved in the proliferation of helper T cells and not CTLs.

Which of the following statements about Ig isotype switching is NOT true? A. Interleukin-4 promotes switching to the IgE isotype by increasing germline transcription of the Cε exon. B. Isotype switching involves recombination of a V(D)J complex with downstream C region genes and the deletion of intervening DNA including other C region genes. C. Activation-induced deaminase (AID) is required for switch recombination. D. The enzymes that mediate isotype switching recognize conserved heptamer and nonamer DNA sequences adjacent to the constant region exons. E. The same recombined V(D)J gene complex is used to encode the antigen-binding region of the antibodies produced by a B cell before and after isotype switching.

D. The enzymes that mediate isotype switching recognize conserved heptamer and nonamer DNA sequences adjacent to the constant region exons.

A 5-year-old boy has a history of recurrent pneumococcal pneumonia, Pneumocystis carinii pneumonia (PCP), and bacterial ear infections. His maternal uncle and an older brother experienced the same symptoms, but he has an older sister who is healthy. Laboratory studies indicate normal numbers of B cells and T cells, and the serum contains mostly IgM and very little IgG. Which of the following abnormalities would NOT be likely in this patient? A. The IgG antibodies that are present are of lower affinity for antigen than of those of a healthy individual. B. Lymph nodes are without well-developed follicles containing germinal centers. C. Macrophage killing of intracellular microbes is impaired. D. There is limited diversity in the repertoire of IgM antibodies produced. E. There is no evidence of somatic mutation of IgM variable regions.

D. There is limited diversity in the repertoire of IgM antibodies produced.

All of the following protein-protein interactions are involved in activation of naive helper T cells by antigen-presenting cells (APCs) EXCEPT: A. Binding of peptide-MHC complexes on the APC to the TCR on the T cell B. Binding of CD4 on the T cell to nonpolymorphic regions of class II MHC molecules on the APC C. Binding of integrins on the T cell with adhesion ligands on the APC D. Binding of B7-2 on the APC with CD28 on the T cell E. Binding of CD40L on the T cell with CD40 on the APC

E. Binding of CD40L on the T cell with CD40 on the APC

The B cell receptor (BCR) complex and the signaling cascades to which it is linked share many similarities with the T cell receptor (TCR) complex and its linked signaling cascades. Which of the following comparisons between BCR and TCR signaling is NOT true? A. There are ITAMs in the cytoplasmic tails of CD3 in the TCR complex and in the cytoplasmic tails of Igα and Igβ in the BCR complex. B. The cytoplasmic tails of membrane Ig and TCR αβ antigen receptors are very short and lack intrinsic signaling functionality. C. Early signaling events induced by antigen binding to both BCR and TCR involve both Src family and Zap-70 family protein tyrosine kinases. D. Phospholipase C-mediated generation of IP3 and DAG occurs downstream of both BCR and TCR signaling. E. CD4/CD8 coreceptors in T cells and the CR2 coreceptor in B cells both enhance responses to antigen by a PI3 kinase-dependent mechanism

E. CD4/CD8 coreceptors in T cells and the CR2 coreceptor in B cells both enhance responses to antigen by a PI3 kinase-dependent mechanism

Which one of the following B cell responses is NOT stimulated by CD40 ligand? A. Association of TRAFs with the cytoplasmic tails of CD40 molecules B. Activation of NF-κB C. Enhanced expression of B7-1 and B7-2 D. Enhanced Ig isotype switch recombinase activity E. Enhanced production of membrane Ig

E. Enhanced production of membrane Ig

Which of the following events does NOT occur within germinal centers? A. Somatic mutation of Ig V genes B. Generation of memory B cells C. B cell proliferation D. Affinity maturation E. Ig gene V(D)J recombination

E. Ig gene V(D)J recombination

Which one of the following statements about the molecule Lck is NOT true? A. It is a member of the Src family of kinases. B. It binds to the cytoplasmic tails of T cell coreceptors CD4 or CD8. C. It phosphorylates ITAM motifs on the CD3 complex. D. It phosphorylates tyrosine residues on Zap-70 and activates it. E. It phosphorylates PIP2 to PIP3 and leads to the activation of Itk.

E. It phosphorylates PIP2 to PIP3 and leads to the activation of Itk.

Which one of the following cell types would be most potent at activating naive T cells? A. Kupffer cells B. B cells C. Follicular dendritic cells D. Neutrophils E. Langerhans cells

E. Langerhans cells

Which pair of molecules is a component of cytolytic T lymphocyte (CTL) granules and is important in the mechanism of CTL killing of target cells? A. Perforin and Fas ligand B. P-selectin and tumor necrosis factor C. Major basic protein and granzyme B D. C9 and interferon-γ E. Perforin and granzyme B

E. Perforin and granzyme B

1. Which one of the following statements about primary and secondary antibody responses is NOT true? A. Antibodies in primary responses generally have lower affinity for antigen than those produced in secondary responses. B. Secondary responses reach peak levels more quickly than primary responses. C. Primary responses require higher concentrations of antigen for initiation than secondary responses. D. Primary responses occur to all types of antigens, but secondary responses mostly occur only to protein antigens. E. Primary responses are characterized by IgG antibodies, whereas secondary responses are dominated by IgM antibodies.

E. Primary responses are characterized by IgG antibodies, whereas secondary responses are dominated by IgM antibodies.

The mechanisms by which TH1 cells protect against microbes include all of the following EXCEPT: A. Secretion of interferon (IFN)-γ, which activates microbicidal functions of macrophages B. Expression of CD40 ligand, which binds to CD40 on macrophages and activates them C. Secretion of IFN-γ, which promotes B cell production of opsonizing antibodies D. Secretion of lymphotoxin and tumor necrosis factor, which enhance neutrophil killing of ingested microbes E. Release of granzyme B, which stimulates apoptosis of bacteria

E. Release of granzyme B, which stimulates apoptosis of bacteria

Which of the following comparisons between TH1 and TH2 cells is true? A. TH1 cells produce interleukin (IL)-1 but not IL-2, and TH2 cells produce IL-2 but not IL-1. B. TH1 cells are class I major histocompatibility complex (MHC) restricted, and TH2 cells are class II MHC restricted. C. The chemokine receptors CXCR3 and CCR5 are more highly expressed on TH2 cells than on TH1 cells. D. TH2 cells are more likely to bind to E-selectin and P-selectin on endothelial cells than are TH1 cells. E. TH1 cells produce interferon (IFN)-γ but not IL-4, and TH2 cells produce IL-4 but not IFN-γ.

E. TH1 cells produce interferon (IFN)-γ but not IL-4, and TH2 cells produce IL-4 but not IFN-γ.

True/False Helper T cells interact with Class I MHC proteins

False

26) If an individual has antibodies in his serum against a particular pathogen, this means that he

Has been exposed to the pathogen or its components

28) In order for T cells to provide help to B cells, the T cell and B cell must

Have linked recognition

4)Which of the following molecules is secreted by Th17 cells after they recognize MHC+Ag and are activated?

IL-17

21)Which of the following would be best able to neutralize botulinum toxin secreted in the g.i tract?

IgA secreted in the mucosa

9)______ antibodies are responsible for allergic reactions.

IgE

16)Which of the following would be produced by a response to T-independent Antigens?

IgM

Which one of the following statements about the molecules B7-1 and B7-2 is NOT true? A. B7-1 and B7-2 expression on antigen-presenting cells (APCs) is upregulated by the presence of "danger" signals, such as lipopolysaccharide, as well as cytokines, such as interferon (IFN)-γ. B. B7-1 and B7-2 are expressed at low levels on some resting APCs. C. Induction of B7-1 usually occurs before the induction of B7-2 in an immune response. D. B7-1 and B7-2 bind to CD28 on T cells and provide "second signals" for naive T cell activation. E. Activated helper T cells can induce expression of B7-1 and B7-2 on APCs via CD40L binding to CD40.

Induction of B7-1 usually occurs before the induction of B7-2 in an immune response.

22)Which of the following is an effector molecule produced by cytotoxic T cells?

Perforin

Which of the following are effector molecules of cytotoxic T cells?

Perforin , Granzymes , Fas

7)Before a B cell can receive help from a T cell, the B cell must

Process and present peptide on Class II MHC

13)B cell isotype switching is important for

Providing antibodies which can perform different effector functions

All of the following molecules act as transcription factors in T cell activation signaling EXCEPT: A. NF-κB B. Jun C. Fos D. NFAT E. Ras

e. ras

Which of the following molecules is NOT important in the interaction between a cytolytic T lymphocyte and a target cell? A. B7-1 B. ICAM-1 C. LFA-1 D. T cell receptor E. Class I MHC

A. B7-1

All of the following assays are used to detect antibody production EXCEPT: A. BrdU (bromodeoxyuridine) assay B. Enzyme-linked immunosorbent assay (ELISA) C. ELISPOT assay D. Hemolytic plaque assay E. Radioimmunoassay (RIA)

A. BrdU (bromodeoxyuridine) assay

Which one of the following signaling molecules, if mutated, would affect B cell maturation and function primarily without affecting T cell function? A. Btk B. Itk C. Tec D. PI-3 kinase E. Zap-70

A. Btk

Which of the following descriptions about affinity maturation is correct? A. Depends on somatic mutation of V genes B. Depends on negative selection of B cells that can bind antigen in the germinal center C. Depends on antigen processing and presentation by dendritic cells within the germinal center D. Depends on the autoimmune regulator (AIRE) gene E. Depends on somatic recombination of Ig V genes

A. Depends on somatic mutation of V genes

Antibody feedback is mediated by which of the following molecules? A. Ig FcγRIIB B. Ig Fcε C. Ig FcγRI D. CR1 E. IgM

A. Ig FcγRIIB

Activated macrophages perform all of the following functions EXCEPT: A. Inhibition of fibroblast proliferation and angiogenesis within damaged tissues B. Production of lysosomal enzymes and reactive oxygen species that kill phagocytosed microbes C. Presentation of antigen to helper T cells D. Secretion of inflammatory cytokines such as tumor necrosis factor and interleukin-1 E. Production of nitric oxide, which helps kill microorganisms

A. Inhibition of fibroblast proliferation and angiogenesis within damaged tissues

Which one of the following statements about humoral immune responses is true? A. Naive B cells are required for initiation of primary responses and memory B cells are required for initiation of secondary responses. B. Antibody responses to bacterial polysaccharide antigens require CD4+ helper T cells. C. Heavy chain isotype switching typically occurs in response to bacterial polysaccharide antigens. D. Affinity maturation does not require helper T cells. E. Antibody-secreting cells generated during a humoral immune response live for only a few hours.

A. Naive B cells are required for initiation of primary responses and memory B cells are required for initiation of secondary responses.

. Which one of the following accurately depicts the correct order of events in a TCR signal transduction pathway? A. TCR → Lck → Zap-70 → LAT → Grb-2 → SOS → Ras → Erk → Fos B. TCR → Lck → Zap-70 → LAT → SOS → Grb-2 → Ras → Erk → Fos C. TCR → Lck → ITK → LAT → Grb-2 → SOS → Ras → Erk → Fos D. TCR → Lck → Zap-70 → LAT → SOS → Grb-2 → Ras → Erk → Jun E. TCR → Lck → Zap-70 → LAT → PLCγ → DAG → calcium release

A. TCR → Lck → Zap-70 → LAT → Grb-2 → SOS → Ras → Erk → Fos

A 23-year-old man who was recently infected by the HIV virus volunteered for investigative studies of his immune response to the virus. Investigators identified cytolytic T lymphocytes (CTLs) in the patient's blood that recognized a particular peptide derived from a protein encoded by the HIV gag gene. Six months later, viral isolates from the patient showed point mutations in the gag gene sequence encoding that peptide. Which of the following statements about the HIV gag mutations is most likely to be correct? A. The patient's CTL response to the virus provided selective pressure for the emergence of virus carrying the mutation. B. The CTL that recognized the original gag-encoded peptide will still be able to recognize the mutated Gag peptide. C. The CTLs specific for the original Gag peptide were incapable of killing HIV- infected cells. D. The gag mutation will enhance the ability of natural killer cells to recognize and kill HIV infected cells. E. The gag mutations have more relevance to the viral evasion of the antibody response rather than the CTL response.

A. The patient's CTL response to the virus provided selective pressure for the emergence of virus carrying the mutation.

Damage to neurons in patients with multiple sclerosis (MS) may be caused by autoreactive T cells that recognize peptides derived from myelin proteins presented by self MHC molecules. These autoreactive T cells secrete interferon (IFN)-γ and promote inflammation, which damages the myelin sheath surrounding neurons. The exact immunodominant epitopes recognized by autoreactive T cells in MS patents have been identified. One potential method of therapy for patients with MS is to administer therapeutic peptides that differ from the immunodominant epitopes by one or two amino acids. Which one of the following statements best describes the basis for this therapeutic approach? A. The therapeutic peptides, called "altered peptide ligands," could inactivate T cells specific for myelin proteins, or drive them to differentiate into T cells that do not produce IFN-γ. B. The therapeutic peptides, called "altered peptide ligands," could interfere with processing of the natural myelin proteins by the patient's antigen-presenting cells. C. The therapeutic peptides could bind to the TCRs of myelin-specific T cells but not to the self MHC molecules, thereby blocking T cell activation. D. The therapeutic peptides could down-regulate MHC expression. E. The therapeutic peptides could replace the damaged myelin and restore neuronal function.

A. The therapeutic peptides, called "altered peptide ligands," could inactivate T cells specific for myelin proteins, or drive them to differentiate into T cells that do not produce IFN-γ.

A 7-month-old boy, the only child of second-degree cousins, saw a pediatrician for immunologic evaluation after developing Pneumocystis carinii pneumonia. Serum IgG, IgM, and IgA levels were normal. Blood cell count showed 10,600 leukocytes/mm3 and 80% lymphocytes; 90% of the lymphocytes were TCR αβ+ CD4+. In vitro lymphocyte- proliferative responses to PHA and anti-CD3 were absent, and the pattern of tyrosine- phosphorylated cytoplasmic proteins after anti-CD3 treatment of the T cells was distinctly abnormal. This boy most likely carries homozygous mutations in the gene encoding which one of the following proteins? A. Zap-70 B. RAG-1 C. CD3 D. Pre-Tα E. TCRα

A. Zap-70

17)Th1 cells secrete cytokines that

Activate macrophages