Chapter 35

Question 1

Immune System

Answer 1

An animal body’s system of defenses against agents that cause disease

Question 2

Innate Immunity

Answer 2

A form of defense common to all animals that is active immediately upon exposure to pathogens and that is the same whether or not the pathogen has been encountered previously

Question 3

Adaptive Immunity

Answer 3

A vertebrate-specific defense that is mediated by B lymphocytes (B cells) and T lymphocytes (T cells) and that exhibits specificity, memory, and self-nonself recognition; also called acquired immunity.

Question 4

Lysozyme

Answer 4

An enzyme that destroys bacterial cell walls; in mammals, found in sweat, tears, and saliva

Question 5

Toll-Like Receptor (TLR)

Answer 5

A membrane receptor on a phagocytic white blood cell that recognizes fragments of molecules common to a set of pathogens

Question 6

Neutrophils

Answer 6

The most abundant type of white blood cell. Neutrophils are phagocytic and tend to self-destruct as they destroy foreign invaders, limiting their life span to a few days

Question 7

Macrophages

Answer 7

A phagocytic cell present in many tissues that functions in innate immunity by destroying microorganisms and in acquired immunity as an antigen-presenting cell

Question 8

Natural Killer Cells

Answer 8

A type of white blood cell that can kill tumor cells and virus-infected cells as part of innate immunity

Question 9

Cytokines

Answer 9

Any of a group of small proteins secreted by a number of cell types, including macrophages and helper T cells, that regulate the function of other cells

Question 10

Interferons

Answer 10

A protein that has antiviral or immune regulatory functions. For example, interferons secreted by virus-infected cells help nearby cells resist viral infection.

Question 11

Complement System

Answer 11

A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis, or directly lyse extracellular pathogens

Question 12

Inflammatory Response

Answer 12

An innate immune defense triggered by physical injury or infection of tissue involving the release of substances that promote swelling, enhance the filtration of white blood cells, and aid in tissue repair and destruction of invading pathogens

Question 13

Histamine

Answer 13

A substance released by mast cells that causes blood vessels to dilate and become more permeable in inflammatory and allergic responses

Question 14

Lymphocytes

Answer 14

A type of white blood cell that mediates immune responses. The two main classes are B cells and T cells.

Question 15

Thymus

Answer 15

A small organ in the thoracic cavity of vertebrates where maturation of T cells is completed

Question 16

T Cells

Answer 16

The class of lymphocytes that mature in the thymus; they include both effector cells for the cell-mediated immune response and helper cells required for both branches of adaptive immunity

Question 17

B Cells

Answer 17

The lymphocytes that complete their development in the bone marrow and become effector cells for the humoral immune response

Question 18

Antigen

Answer 18

A substance that elicits an immune response by binding to receptors of B cells. antibodies, or T cells

Question 19

Antigen Receptor

Answer 19

The general term for a surface protein, located on B cells and T cells, that binds to antigens, initiating adaptive immune responses. The antigen receptors on B cells are called B cell receptors, and the antigen receptors on T cells are called T cell receptors.

Question 20

Epitope

Answer 20

A small, accessible region of an antigen to which an antigen receptor or antibody binds; also called an antigenic determinant.

Question 21

Antibody/Immunoglobin (Ig)

Answer 21

A protein secreted by plasma cells (differentiated B cells) that binds to a particular antigen; also called immunoglobulin. All antibodies have the same Y-shaped structure and in their monomer form consist of two identical heavy chains and two identical light chains

Question 22

Major Compatibility Complex Molecule (MHC)

Answer 22

A host protein that functions in antigen presentation. Foreign MHC molecules on transplanted tissue can trigger cell responses that may lead to rejection of the transplant.

Question 23

Antigen Presentation

Answer 23

The process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell

Question 24

Primary Immune Response

Answer 24

The initial adaptive immune response to an antigen, which appears after a lag of about 10 to 17 days

Question 25

Secondary Immune Response

Answer 25

The adaptive immune response elicited on second or subsequent exposures to a particular antigen. The secondary immune response is more rapid, of greater magnitude, and of longer duration than the primary immune response.

Question 26

Humoral Immune Response

Answer 26

The branch of adaptive immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids

Question 27

Cell-Mediated Immune Response

Answer 27

The branch of adaptive immunity that involves the activation of cytotoxic T cells, which defend against infected cells

Question 28

Helper T Cell

Answer 28

A type of T cell that, when activated, secretes cytokines that promote the response of B cells (humoral response) and cytotoxic T cells (cell-mediated response) to antigens

Question 29

Antigen-Presenting Cell

Answer 29

A cell that upon ingesting pathogens or internalizing pathogen proteins generates peptide fragments that are bound by class II MHC molecules and subsequently displayed on the cell surface to T cells. Macrophages, dendritic cells, and B cells are the primary antigen-presenting cells.

Question 30

Cytotoxic T Cells

Answer 30

A type of lymphocyte that, when activated, kills infected cells as well as certain cancer cells and transplanted cells

Question 31

Immunization

Answer 31

The process of generating a state of immunity by artificial means. In active immunization, also called vaccination, an inactive or weakened form of a pathogen is administered, inducing B and T cell responses and immunological memory. In passive immunization, antibodies specific for a particular pathogen are administered, conferring immediate but temporary protection.

Question 32

Autoimmune Disease

Answer 32

An immunological disease in which the immune system turns against self