Ch 35: The Immune System

Question 1

Which secretion is not a barrier that prevents pathogens from entering the body?

Lysozyme
Ear wax
Antigens
Mucus

Answer 1

antigens

Question 2

True or false? The leukocytes of the innate immune system are B cells, macrophages, and neutrophils.

Answer 2

False. The leukocytes of the innate immune system are mast cells, macrophages, and neutrophils.

Question 3

How do cells involved in the innate immune response detect the presence of pathogens?

Answer 3

Leukocytes recognize unique molecules on pathogens.

Question 4

_________ are leukocytes that can engulf and digest a pathogen.

Answer 4

Macrophages

Question 5

Which of the following statements best describes the role of mast cells in the inflammatory response?

a. ) They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream.
b. ) They release chemicals that constrict blood vessels at some distance from the wound site.
c. ) They secrete substances that degrade bacterial cell walls and engulf and digest the invaders.
d. ) They release cytokines to stimulate the release of additional neutrophils and macrophages.

Answer 5

a.) They release chemicals that dilate blood vessels near the wound site, allowing blood components to enter the region from the bloodstream.

Question 6

Which of the following events occurs first when a wound that breaks the skin has occurred?

a. ) Mast cells secrete chemical messengers to regulate blood flow to the wound.
b. ) Neutrophils secrete substances that degrade bacterial cell walls.
c. ) Macrophages present bacterial proteins as antigens on their plasma membrane.
d. ) Platelets release proteins that form clots and decrease bleeding.

Answer 6

d.) Platelets release proteins that form clots and decrease bleeding.

Question 7

What cellular structure would you predict to be in abundance in plasma cell that function to sythesize large quantities of secreted proteins (antibodies)?

Answer 7

rough endoplasmic reticulum

Question 8

What cellular structure would you predict to be in abundance in macrophages that function in antigen destruction?

Answer 8

lysosomes

Question 9

Which cell type provides long term immunity after a vaccination?

Answer 9

memory cells

Question 10

Sort the items into the appropriate bins depending on whether they are involved in the humoral response, the cell-mediated response, or both the humoral and the cell-mediated responses.

antibodies
antigen-presenting cells
B cells
cytotoxic T-cells
helper T-cells and cytokines
memory cells
plasma cells

Answer 10

Humoral response:

• B cells
• Antibodies
• Plasma cells

Cell-Mediated Response:
- Cytotoxic T cells

Both:

• Helper T cells and cytokines
• Memory cells
• Antigen-presenting cells

Question 11

Cytotoxic T cells are the effector cells in the cell-mediated immune response. The diagram below summarizes the interaction of a cytotoxic T cell and its target cell.

Answer 11

see image

Question 12

B cells are involved in the humoral immune response. The flowchart below summarizes the steps involved in B cell activation.

Answer 12

see image

Question 13

All animals have innate immunity. Only _________ have adaptive immunity.

In jawed vertebrates, innate immune defenses coexist with the more recently evolved system of adaptive immunity. Because most of the recent discoveries regarding vertebrate innate immunity have come from studies of mice and humans, we’ll focus here on mammals. In this section we’ll consider the innate defenses that are similar to those found among invertebrates—barrier defenses, phagocytosis, and antimicrobial peptides—as well as some that are unique to vertebrates, such as natural killer cells, interferons, and the inflammatory response.

Answer 13

vertebrates

Question 14

What are the two elements of adaptive immunity?

Answer 14

humoral response: antibodies defend against infection in body fluids/ extracellular spaces

cell-mediated response: cytotoxic cells defend against infection in body cells

Question 15

The adaptive response relies on T cells and B cells, which are types of white blood cells called lymphocytes. Like all blood cells, lymphocytes originate from ____ _____ in the bone marrow. Some migrate from the bone marrow to the thymus, an organ in the thoracic cavity above the heart. These lymphocytes mature into T cells. Lymphocytes that remain and mature in the bone marrow develop as B cells.

Answer 15

stem cells

Question 16

An antigen is any substance that….

Answer 16

…elicits a B or T cell response.

Question 17

Each antigen receptor binds to just ___ part of one molecule from a particular ________, such as a species of bacteria or strain of virus.

Answer 17

one

pathogen

Question 18

The cells of the immune system produce millions of different antigen receptors. A given lymphocyte, however, produces just one variety; all of the antigen receptors made by a single B or T cell are _________.

Answer 18

identical

Question 19

Although drawings of B and T cells typically include just a few antigen receptors, a single B or T cell actually has about _____ antigen receptors on its surface.

Answer 19

100,000

Question 20

The small, accessible portion of an antigen that binds to an antigen receptor is called an _______. An example is a group of amino acids in a particular protein. A single antigen usually has several ________, each binding a receptor with a different specificity.

Answer 20

epitope

epitopes

Question 21

Each B cell antigen receptor is a Y-shaped protein consisting of four __________ chains: two identical heavy chains and two identical light chains. Disulfide bridges link the chains together.

Answer 21

polypeptide

Question 22

Binding of a B cell antigen receptor to an antigen is an early step in B cell activation, leading eventually to formation of cells that secrete a soluble form of the receptor. This secreted protein is called an antibody, also known as an __________. Antibodies have the same Y-shaped structure as B cell antigen receptors, but lack a membrane anchor. As you’ll see later, antibodies provide a direct defense against pathogens in body fluids.

Answer 22

immunoglobulin

Question 23

The antigen-binding site of a membrane-bound receptor or antibody has a unique shape that provides a lock-and-key fit for a particular _______. This stable interaction involves many noncovalent bonds between an epitope and the surface of the binding site. Differences in the amino acid sequences of variable regions provide the variation in binding surfaces that enables binding to be highly specific.

B cell antigen receptors and antibodies bind to epitopes of intact antigens in the blood and lymph. They can bind to antigens on the surface of pathogens or ____ in body fluids.

Answer 23

epitope

free

Question 24

For a T cell, the antigen receptor consists of two different polypeptide chains, an α chain and a β chain, linked by a disulfide bridge. Near the base of the T cell antigen receptor (often called simply a T cell receptor) is a transmembrane region that anchors the molecule in the cell’s plasma membrane. At the outer tip of the molecule, the variable (V) regions of the α and β chains together form a single antigen-binding site. The remainder of the molecule is made up of the ________ (C) regions.

Answer 24

constant

Question 25

Whereas the antigen receptors of B cells bind to epitopes of intact antigens protruding from pathogens or circulating free in body fluids, antigen receptors of T cells bind only to fragments of antigens that are displayed, or presented, on the surface of host cells. The host protein that displays the antigen fragment on the cell surface is called a major histocompatibility complex (MHC) molecule. By displaying _______ _________, MHC molecules are essential for antigen recognition by T cells.

Answer 25

antigen fragments

Question 26

The display of protein antigens occurs when a pathogen infects a cell of the animal host or when an immune cell engulfs pathogen proteins or a whole pathogen. Inside the animal cell, enzymes cleave each antigen into antigen fragments, which are small peptides. Each antigen fragment binds to an MHC molecule, which transports the bound peptide to the ____ ________. The result is antigen presentation, the display of the antigen fragment in an exposed groove of the MHC protein.

Answer 26

cell surface

Question 27

Inside the host cell, an antigen fragment from a pathogen binds to an MHC molecule and is brought to the cell surface, where it is displayed. The combination of MHC molecule and antigen fragment is recognized by a _ ____.

In effect, antigen presentation advertises the fact that a host cell contains a foreign substance. If the cell displaying an antigen fragment encounters a T cell with the right specificity, the interaction of an MHC molecule, an antigen fragment, and an antigen receptor triggers an adaptive immune response.

Answer 27

T cell

Question 28

B cells could kill pathogens outside of cells, but cytotoxic T cells kill pathogens which are ______ cells.

Answer 28

INSIDE

Question 29

Despite the enormous variety of antigen receptors, only a tiny fraction are specific for a given epitope. How, then, does an effective adaptive response develop? To begin with, an antigen is presented to a steady stream of lymphocytes in the lymph nodes until a match is made. A successful match between an antigen receptor and an epitope initiates events that activate the lymphocyte bearing the receptor.
Once activated, a B cell or T cell undergoes multiple cell divisions. For each activated cell, the result of this proliferation is a clone, a population of cells that are identical to the original cell. Some cells from this clone become effector cells, mostly short-lived cells that take effect immediately against the antigen and any pathogens producing that antigen. For B cells, the effector forms are _______ _____, which secrete antibodies.

Answer 29

plasma cells

Question 30

For T cells, the effector forms are helper T cells and cytotoxic T cells. The remaining cells in the clone become memory cells, long-lived cells that can give rise to effector cells if the same antigen is encountered later in the animal’s life.

Figure 35.11 summarizes the proliferation of a lymphocyte into a clone of cells in response to binding to an antigen, using B cells as an example. This process is called clonal selection because an encounter with an antigen selects which lymphocyte will divide to produce a ______ ___________ of thousands of cells specific for a particular epitope.

Answer 30

clonal population

Question 31

In the inflammatory immune response, what does the release of histamine do?

Answer 31

increase the permeability of nearby blood vessels