Exam 2: Set 1 Flashcards
There are five primary classes of immunoglobulins are IgG, IgM, IgA, IgD and IgE. These classes are distinguished by the type of heavy chain found in the molecule. Differences in heavy chain polypeptides allow these immunoglobulins to function in different types of immune responses and at particular stages of the immune response. Which of the following is the first immunoglobulin heavy chain class to be expressed on the surface of a newly produced B-cell is:
A. IgA B. IgD C. IgE D. IgG E. IgM
E. IgM
Each B cell has approximately 105 B cell receptors in its plasma membrane which are stably associated with a complex of transmembrane proteins that activate intracellular signaling
pathways. When a naïve B cell is activated by antigen (with the aid of a helper T cell), it proliferates and differentiates into an antibody-secreting effector cell. Such cells make and secrete large amounts of soluble (rather than membrane-bound) antibody, which has the same unique antigen-binding site as the cell-surface antibody that served earlier as the antigen receptor. A B-cell is able to make membrane-attached or secreted versions of BCR (antibody) using which of the following?
A. Different gene pools.
B. Differential splicing.
C. Different heavy chain class but the same light chain.
D. Different light chain class but the same heavy chain.
E. F(ab’)2 fragments.
B. Differential splicing.
BCR is attached to the membrane through the carboxy termini of the paired heavy chains. The cell-surface heavy chain protein is made in such a way that the carboxy terminus of the protein contains a transmembrane domain and a cytoplasmic tail. The cytoplasmic region of surface IgM consists of which of the following?
A. A single H chain constant region domain. B. A light chain. C. 110 amino acids. D. 3 amino acids. E. Carbohydrate.
D. 3 amino acids.
Gamma delta T cells are the prototype of “unconventional” T cells. They are defined by expression of heterodimeric T-cell receptors (TCRs) composed of gamma and delta chains. This sets them apart from the classical and much better known CD4+ helper T cells and CD8+ cytotoxic T cells that express alpha/beta TCRs. What is the percentage of human peripheral blood T-cells bearing a gamma/delta T- cell receptor?
A. 30–80%. B. 1-5%. C. 100%. D. 0%. E. Only present during mycobacterial infections.
B. 1-5%.
The heterodimeric T-cell surface receptors are produced following somatic rearrangement of the T-cell receptor (TCR) genes (alpha, beta, delta, and gamma). This process is vital to proliferation of T-cells in normal immune function, but can be exploited to aid in the distinction between reactive (benign) versus neoplastic processes of T-cell proliferation. A reactive, benign T-cell proliferation is characterized by polyclonal expansion of T-cells whereas a malignant process is characterized by clonal expansion of one T-cell population. Which of the following gene segments is not present in alpha chain gene of TCR?
A. Joining (J). B. Diversity (D). C. Variable (V). D. Constant (C). E. TCR beta chain.
B. Diversity (D).
There are more than 200 alleles of some human MHC class I and class II genes, each allele being present at a relatively high frequency in the population. So there is only a small chance that the corresponding MHC locus on both the homologous chromosomes of an individual will have the same allele. Expression of MHC genes is characterized by which of the following?
A. Codominant expression
B. Dominant expression for maternal genes.
C. Dominant expression for paternal genes.
D. Dependence on thymic selection.
E. Dependence on the antigenic exposure of the individual
A. Codominant expression
The B-cell receptor (BCR) for antigen is a key sensor required for B-cell development, survival, and activation. Following the binding of antigens, the BCR transduces signals and internalizes antigens for processing and presentation, both of which are required for initiating an effective
antibody response. Which of the following are molecules mediating signal transduction after antigen binding to BCR on the surface of B cells?
A. IgFc B. Ig-alpha and Ig-beta C. MHC D. CD4 E. CD8
B. Ig-alpha and Ig-beta
The immune system has a near limitless capacity for detecting abnormalities. This remarkable ability for “selfinterrogation” is achieved by the related structures of two molecules, immunoglobulins and T cell receptors (TCRs). Initial descriptions of TCRs were made 30 years ago primarily through similarity with immunoglobulin DNA sequences. From this beginning, a clearer picture of TCR structure has developed. Which of the following is correct about TCR?
A. TCR is produced by alternative splicing B. TCR is a tetramer C. TCR is a homodimer D. TCR is a heterodimer E. TCR is a single chain molecule
D. TCR is a heterodimer
The TCR, through its complementarity-determining regions or CDRs, endows the T cell with the ability to recognize and respond to foreign or “non self” antigens. Antigen presenting cells (APCs) digest pathogens and display their fragments on major histocompatibility complex (MHC) molecules. This MHC/antigen complex binds to the TCR leading to T cell activation. Which of the following is a component of the TCR receptor complex responsible for signal transduction?
A. The TCR alpha chain. B. The TCR beta chain. C. CD1. D. CD2. E. CD3.
E. CD3.
The main function of major histocompatibility complex (MHC) class II molecules is to present processed antigens, which are derived primarily from exogenous sources, to CD4+ T- lymphocytes. MHC class II molecules thereby are critical for the initiation of the antigen-specific immune response. Constitutive expression of MHC class II molecules is confined to which of the following cells?
A. Only dendritic cells and macrophages
B. B cells, dendritic cells and macrophages
C. Only follicular dendritic cells
D. Virtually all nucleated cells in the body
E. Only B cells and dendritic cells
B. B cells, dendritic cells and macrophages
There are two categories of lymphocytes known as B lymphocytes and T lymphocytes. These are commonly referred to as B cells and T cells. Progenitors of both cell types originate from stem cells in the bone marrow. From there, committed T cell precursor cells travel to the thymus via blood, where they proliferate and generate naive T cells. In contrast, committed precursors of B lymphocytes remain in the bone marrow, where they develop into B cells. Which of the following is characteristic of B cells but not T cells?
A. Expression of Class I MHC B. Expression of CD3 C. Expression of measles virus receptor D. Polyclonal activation by super antigens E. Expression of surface immunoglobulin
E. Expression of surface immunoglobulin
T cells are generated in the thymus and are programmed to be specific for one particular antigen. Once they leave the thymus, they circulate throughout the body until they recognize their cognate antigen on the surface of APCs. The TCR on both CD4+ helper T cells and CD8+ cytotoxic T cells binds to the antigen as it is held in a structure called the MHC complex, on the surface of the APC. When a resting naive T-cell engages its specific MHC/peptide complex displayed on the surface of a fibroblast which of the following happens to T cell?
A. It undergoes blast cell formation.
B. It produces large amounts of IL-2
C. It proceeds from Go to G1 in the cell cycle
D. It becomes anergic cell
E. It secretes IL-12 and Th1 cells are produced
D. It becomes anergic cell
