Exam 2: Set 3 Flashcards
The immune system has a near limitless capacity for detecting abnormalities. This remarkable ability for self-interrogation is achieved by the related structures of two molecules, immunoglobulins and T cell receptors (TCR). The TCR, through its complementary determining regions (CDRs), endows the T cell with the ability to recognize and respond to foreign or “non self” material. The basic structure of a T cell receptor consists of
A. a membrane-bound alpha/beta or gamma/delta heterodimer.
B. a complex of disulfide-linked heavy and light chains.
C. covalently linked CD3 and CD247 molecules.
D. peptide-MHC complexes.
E. soluble antigen-binding homodimers.
A. a membrane-bound alpha/beta or gamma/delta heterodimer.
Lymphocyte homeostasis in resting lymph nodes (LNs) is maintained by the entry of circulating lymphocytes through high endothelial venules (HEVs) and exit through lymphatic vessels. After crossing the HEVs, B cells rely on their prominent CXCR5 expression to access the LN follicle. Migration of a B lymphocyte to specific sites (such as a lymph node) is dependent in part on the
use of
A. antibodies. B. CD8. C. CD3. D. complement. E. selectins.
E. selectins.
An 8-year-old girl presents with a history of recurrent pneumonia (4 episodes over 2 years). At the age of 4 years and 8 months she had suffered from the first episode of middle lobar bronchopneumonia requiring hospitalization. Since a proper immune response to pathogens requires a Th1 induction and this process determines up-regulation of the expression of the IL- 12 receptor (IL-12R), β2 chain mRNA expression in polymorphonuclear blood cells (PMNC) was evaluated in vitro. No expression of IL-12R β2 transcript was found in patient’s cells. In aberrant IL-12 signaling pathway, which of the following will not be translocated into PMNC nucleus to regulate cell transcription?
A. JAK B. Ras C. SH2-containing adapter proteins D. STAT dimers E. tyrosine kinase
D. STAT dimers
Antigen presenting cells (APCs) digest pathogens and display their fragments for recognition by T cells. After antigen binds to the TCR, other co-stimulatory molecules are engaged leading to T cell activation, proliferation, differentiation, apoptosis, and/or cytokine release. When co- expressed with CD8 molecules, TCR is restricted to recognizing and binding peptide fragments associated with which of the following molecule?
A. CD3 molecules. B. CD4 molecules. C. MHC class I molecules. D. MHC class II molecules. E. MHC class III molecules.
C. MHC class I molecules.
Somatic recombination of TCR genes in immature thymocytes results in some cells with useful TCR specificities, but also many with useless or potentially self-reactive specificities. Thus thymic selection mechanisms operate to shape the T-cell repertoire. Thymocytes that have a TCR with low affinity for self-peptide–MHC complexes are positively selected to further differentiate and function in adaptive immunity, whereas useless ones die by neglect. Positive selection refers to which of the following mechanisms?
A. the ability of single positive cells to bind both MHC class I and II.
B. cortical thymocytes’ acquisition of TCR.
C. migration of stem cells to the thymus to become T cells.
D. programmed cell death of single positive T cells.
E. recognition of MHC by CD4+CD8+ thymocytes.
E. recognition of MHC by CD4+CD8+ thymocytes.
Spleen is the largest lymphatic organ and it is important for many functions. The most important are proliferation and differentiation of lymphocytes and destruction of senescent erythrocytes. It also serves as storage of blood which can be used in hypovolemia (decreased blood volume due to bleeding or long-lasting physical strain). The white pulp of the spleen is enriched in which of the following?
A. Erythrocytes B. CD4+CD8+ T cells binding to MHC C. NK cells recognizing targets D. plasma cells secreting immunoglobulin E. precursor cells developing into mature B cells
D. plasma cells secreting immunoglobulin
In a patient who later developed an allergy to a certain antigen, the initial response to the antigen consisted of immunoglobulin of the lgM class. However, over time, antigen-specific lgE came to be predominant. This change from an lgM to an lgE response is caused by which of the following mechanisms?
A. Affinity maturation B. allelic exclusion C. isotype switching D. junctional diversity E. somatic hypermutation
C. isotype switching
The MMR vaccine can be given to babies as young as 6 months old if they will be traveling internationally. These children should still get the recommended routine second and third doses at 12–15 months and 4–6 years of age, respectively, but can get the second dose as early as 4 weeks after the first if they will still be traveling and at risk. When exposed to the MMR vaccine for the first time, a baby already possesses B cells with immunoglobulin specific for MMR antigens. This finding is best explained by which of the following?
A. antigen-independent immunoglobulin gene rearrangements
B. antigen stimulation of T cell cytokine production
C. maternally derived antibodies to that antigen
D. memory B cells that recognize the antigen
E. somatic hypermutation of immunoglobulins
A. antigen-independent immunoglobulin gene rearrangements
Serum immunoglobulins containing both maternally and paternally derived V light chains are found within an individual. A given B cell, however, expresses only maternally derived or paternally derived V chains but never both. This finding is the result of which of the following mechanisms?
A. allelic exclusion B. antibody diversity C. isotype switching D. junctional diversity E. random VD and VDJ joining
A. allelic exclusion
Nearly every DNA polymerase characterized to date exclusively catalyzes the incorporation of mononucleotides into a growing primer using a DNA or RNA template as a guide to direct each incorporation event. There is, however, one unique DNA polymerase designated terminal deoxynucleotidyl transferase (TdT) that performs DNA synthesis using only single-stranded DNA as the nucleic acid substrate. What is the role of this polymerase in development of antibody diversity?
A. add/remove nucleotides of V, D, and J genes.
B. fuse VD and J segments together in heavy chains.
C. increase binding affinity of antibody for antigen.
D. join CL to CH1, CH2, CH3, or CH4 domains.
E. transfer VL alleles from maternal to paternal chromosomes.
A. add/remove nucleotides of V, D, and J genes.
Most effective vaccines that are in use today generate protective, antigen-specific B cell memory. To be effective, memory B cells must target the right antigen, express the appropriate antibody class and bind to their antigen with sufficiently high affinity to provide the host with long-term immune protection. These three cardinal attributes of antigen-specific B cell memory emerge progressively under the cognate guidance of T follicular helper cells (TFH cells) following initial priming and secondary restimulation with antigen in vivo. When a memory B cell is restimulated by its specific antigen, small point mutations that accumulate in the DNA encoding variable regions of both light and heavy chains may result in which of the following?
A. antigen-stimulated VDJ joining and new antigen specificity.
B. change from production of lgM to lgG.
C. DNA chromosomal rearrangement and altered antigen specificity.
D. inactivation of either the maternal or paternal VL and VH allele.
E. generation of antibody with increased binding affinity for its epitope.
E. generation of antibody with increased binding affinity for its epitope.
Gamma/delta T cells are a distinct subgroup of T cells containing TCR gamma and TCR delta chains with diverse structural and functional heterogeneity. As a bridge between the innate and adaptive immune systems, gamma/delta T cells participate in various immune responses during cancer progression. Because of their direct/indirect antitumor cytotoxicity and strong cytokine production ability, the use of gamma/delta T cells in cancer immunotherapy has received a lot of attention over the past decade. Which of the following correctly describes the properties and function of gamma/delta T cells?
A. They contain very extensive antigen recognition repertoires.
B. They express surface markers that are also characteristic of NK cells.
C. They generate memory when recognizing antigen on multiple occasions.
D. They migrate preferentially to respiratory or organs, skin, and peritoneal cavity.
E. They respond more slowly to antigen than do alpha/beta T cells.
D. They migrate preferentially to respiratory or organs, skin, and peritoneal cavity.
