Immunology Chapter 3 - Antigen Capture and Presentation to Lymphocytes

Which type of antigen-presenting cell is most important for activating naive T cells? A. Macrophage B. Dendritic cell C. Endothelial cell D. B lymphocyte E. Epithelial cell

B. Dendritic cell

. Which of the following is the main criterion that determines whether a protein is processed and presented via the class I MHC pathway in an antigen-presenting cell (APC)? A. Encoded by a viral gene B. Present in an acidic vesicular compartment of the APC C. Present in the cytosol of the APC D. Internalized into the cell from the extracellular space E. Small in size

C. Present in the cytosol of the APC

What cells are considered APC's?

Denditric cell B-cell Macrophages

Antigen presentation by what cell is helpful in the initiation of T-cell response to protein antigens?

Dendritic cell

What is the most important/effective APC?

Dendritic cell

What Class I loci are found in humans?

HLA-A HLA-B HLA-C

Plasmacytoid dendrites are the major source of what secreted compound?

Type I interferon

Which polypeptide chain in MHC Class I molecules are variant?

alpha 1 and alpha 2

What domain of MHC Class I molecules form the peptide binding site?

alpha 1 and beta 1

Which polypeptide chain in MHC Class II molecules are invariant?

alpha 3

What domains of MHC Class II molecules have the CD4 co-receptor site?

alpha-2 and beta-2

What allows for antigen peptides to fit inside the pocket of MHC molecules?

anchor residues: Amino acids

What are the two major populations of dendritic cells?

1. Classical 2. Plasmacytoid

What are some of the properties of MHC genes and proteins?

1. Highly polymorphic: many alleles present in population 2. Codominant expression: both parent gene is expressed

How do antigens enter dendritic cells?

1. Phagocytosis 2. Receptor mediated endocytosis

What length can MHC Class II molecules hold?

10-30 AA

What TLR are commonly found on classical dendritic cells?

4,5,8

What peptide length can MHC class I molecule handle?

7-8 amino acid long

12. Which one of the following molecules does NOT play an important role in the class II MHC pathway of antigen presentation? A. B2-Microglobulin B. Cathepsin C. Invariant chain D. HLA-DM E. Calnexin

A. B2-Microglobulin

In the class I MHC pathway of antigen presentation, peptides generated in the cytosol are translocated into the endoplasmic reticulum in which of the following ways? A. By ATP-dependent transport via the transporter associated with antigen-processing (TAP) 1/2 pump B. By passive diffusion C. By receptor-mediated endocytosis D. Through membrane pores E. Via the proteasome

A. By ATP-dependent transport via the transporter associated with antigen-processing (TAP) 1/2 pump

4. A helper T cell response to a protein antigen requires the participation of antigen-presenting cells that express which of the following types of molecules? A. Class II MHC and costimulators B. Class I MHC and CD4 C. Class II MHC and CD8 D. CD4 and costimulators E. Class II MHC and CD4

A. Class II MHC and costimulators

Cells that capture microbial antigens and display them for recognition are known as what?

Antigen presenting cell

What is the major function of plamacytoid dendritic cells?

Antiviral innate immunity

Antigen presentation by what cells is helpful in the humoral immune response?

B-cell

A young adult is exposed to a virus that infects and replicates in mucosal epithelial cells of the upper respiratory tract. One component of the protective immune response to this viral infection is mediated by CD8+ cytolytic T lymphocytes (CTLs), which recognize and kill virus-infected cells. The CTLs can recognize and kill the infected cells because: A. In response to interferon- secreted during the innate immune response to the virus, the mucosal epithelial cells express class II MHC, with bound viral peptides, on their cell surfaces. B. Mucosal epithelial cells, like all nucleated cells, express class I MHC molecules and are able to process cytoplasmic viral proteins and display complexes of class I MHC and bound viral peptides on their cell surfaces. C. Antibodies specific for viral antigens bind to these antigens on infected cell surfaces and engage Ig Fc receptors on the CTL, thereby targeting the CTL to the infected cells. D. Virus-infected mucosal epithelial cells migrate to draining lymphoid tissues, where they present viral peptide antigens to naive CD8+ T cells. E. Viral infection of the mucosal epithelial cells stimulates them to express E-selectin, which promotes CD8+ T cell adhesion.

B. Mucosal epithelial cells, like all nucleated cells, express class I MHC molecules and are able to process cytoplasmic viral proteins and display complexes of class I MHC and bound viral peptides on their cell surfaces.

Where are plasmacytoid dendritic cells found?

Blood and tissues

Antigen-presenting cells (APCs) perform which of the following functions in adaptive immune responses? A. Display major histocompatibility complex (MHC)-associated peptides on their cell surfaces for surveillance by B lymphocytes B. Initiate T cell responses by specifically recognizing and responding to foreign protein antigens C. Display MHC-associated peptides on their cell surfaces for surveillance by T lymphocytes D. Display polysaccharide antigens on their cell surfaces for surveillance by B lymphocytes E. Secrete peptides derived from protein antigens for binding to T cell antigen receptors

C. Display MHC-associated peptides on their cell surfaces for surveillance by T lymphocytes

The production of antibodies requires the activation of what type of T-cell?

CD4 T-cell

In order to kill infected cells what type of T-cell must be activated?

CD8 T-cell

The majority of dendritic cells belong to which subtype?

Classical

Expression of MHC class II molecules is increased by the secretion of what compounds?

Cytokines

. Naive CD8+ T cells require signals in addition to T cell receptor recognition of peptide-MHC to become activated and differentiate into cytolytic T cells. These signals are called costimulatory signals and are provided by professional antigen-presenting cells (APCs), such as dendritic cells. If a virus infects epithelial cells in the respiratory tract but does not infect professional APCs, what process ensures that naive T cells specific for viral antigens will become activated? A. Cross-reactivity, whereby the naive CD8+ T cell recognizes a self antigen that is structurally similar to a viral antigen presented by dendritic cells B. Crossover, whereby part of the viral genome is exchanged with part of one chromosome of the host C. Crosstalk, whereby signals generated by the virus binding to class I MHC molecules intersect with T cell receptor signaling pathways D. Cross-presentation, whereby infected epithelial cells are captured by dendritic cells, and the viral proteins originally synthesized in the epithelial cells are processed and presented in association with class I MHC molecules on the dendritic cell E. Cross-dressing, whereby viral infection of the epithelial cell stimulates the expression of surface molecules that are typically found only on dendritic cells

D. Cross-presentation, whereby infected epithelial cells are captured by dendritic cells, and the viral proteins originally synthesized in the epithelial cells are processed and presented in association with class I MHC molecules on the dendritic cell

A child who suffers from a persistent viral infection is found to have a deficiency in lymphocyte production and very few T and B cells. Other bone marrow-derived cells are produced in normal numbers, and MHC molecule expression on cells appears normal. Transfusion of mature T cells from an unrelated donor who had recovered from a previous infection by the same virus would not be expected to help the child clear his infection. Which one of the following is a reasonable explanation for why this therapeutic approach would fail? A. Viral infections are cleared by antibodies, not T cells. B. The patient's own immune system would destroy the transfused T cells before they could respond to the viral infection. C. T cells recognize peptides, not viral particles. D. Donor T cell viral antigen recognition is restricted by MHC molecules not expressed in the patient. E. In responding to the previous infection, the donor would have used up all his T cells specific for that virus.

D. Donor T cell viral antigen recognition is restricted by MHC molecules not expressed in the patient.

Which of the following statements about the antigen-presenting function of macrophages is NOT correct? A. Macrophages are particularly important at presenting peptides derived from particulate or opsonized antigens that are internalized by phagocytosis. B. Macrophages become activated by the helper T cells to which they present microbial peptides, and as a result of this activation they become efficient at killing the microbes. C. Resting macrophages express low levels of class II MHC molecules, but higher class II MHC expression is induced on activation by the T cells to which they present antigen. D. Macrophages express highly variable, high-affinity receptors for many different antigens, and these receptors facilitate the internalization of the antigens for processing and presentation. E. Macrophages present antigen to T cells in lymphoid organs and many nonlymphoid organs.

D. Macrophages express highly variable, high-affinity receptors for many different antigens, and these receptors facilitate the internalization of the antigens for processing and presentation.

1Which one of the following statements about T cell tolerance to self proteins is accurate? A. Self proteins are not presented by the class I pathway because only microbial proteins, and not self proteins, are ubiquinated in the cytosol. B. Peptides derived from self proteins are not presented by the class I or class II pathways because MHC molecules are expressed only in response to infections. C. Self proteins are not presented by the class II pathway because endosomal acidic proteases digest microbial proteins but not eukaryotic proteins. D. Self peptide/self MHC complexes are formed and displayed by antigen-presenting cells in both class I and class II MHC pathways, but T cells that recognize these complexes usually are not present or are functionally inactive. E. Peptides derived from self proteins are not displayed by MHC molecules because they usually are displaced by the more abundant microbial peptides.

D. Self peptide/self MHC complexes are formed and displayed by antigen-presenting cells in both class I and class II MHC pathways, but T cells that recognize these complexes usually are not present or are functionally inactive.

Maturing dendritic cells that migrate to a lymph node from peripheral tissues end up mainly in: A. Follicles B. High endothelial venules C. The medullary sinus D. T cell zones E. Efferent arterioles

D. T cell zones

. In the class I MHC pathway of antigen presentation, cytoplasmic proteins are tagged for proteolytic degradation by covalent linkage with which of the following molecules? A. Calreticulin B. Nuclear factor (NF)-B C. Tapasin D. Ubiquitin E. Calnexin

D. Ubiquitin

During what stage of immunity is macrophage antigen presentation increased?

Effector phase of cell mediated immunity

Where are dendritic cells usually found?

Epithelia and subepithelial tissues

What cytokine(s) induce MHC Class II expression in macrophages?

IFN-gamma

What is MHC restriction?

Individuals can only see peptides when they are displayed by their own MHC molecules

What is the major function of classical dendritic cells?

Induction of T-cell responses

Epidermal dendritic cells are known as ___________________.

Langerhan cell

Upon activation what occurs to dendritic cells that allow then to travel to the T-cell zone of lymph nodes?

Loss affinity for epithelia and express CCR7

Where does antigen recognition take place?

Lymph node

On what type of cells are MHC Class I molecules found?

MHC Class I cells are found in all nucleated cells

How many peptides can an MHC molecule present at a time?

Only 1

What type of antigens do T-cells recognize?

Peptides FRAGEMENTST

What type of antigens do B-cells recognize?

Protein Lipids Polysaccharides Nucleic Acids

What is the adaptive immune response initiated by?

Recognition of antigen by antigen receptor of lymphocytes

How do T-cells recognize peptide antigens?

Recognize via display and presentation via MHC molecules

What TLR are commonly found on Plasmacytoid dendritic cells?

TLR 7,9

The peptide binding groove of MHC Class I molecules is made by which polypeptide chains?

alpha 1 and alpha 2

What is found in the alpha 3 domain of MHC Class I molecules?

site that binds CD8 T-cell coreceptor