Chapter 15: Nonspecific Host Defense Mechanisms

Question 0

Define antibody.

Answer 0

Produced by lymphocytes in response to an antigen.

Question 1

Define host defense mechanisms

Answer 1

Are general and serve to protect the body against many harmful substances; are either specific or nonspecific. 1st and 2nd lines of defense are nonspecific. 3rd line of defense is very specific.

Question 2

Define antigen.

Answer 2

Special proteins produced in response to the presence of foreign substances; they stimulate the production of specific antibodies (antibody-generating).

Question 3

Define lysozyme.

Answer 3

A membrane-bound vesicle found in the cytoplasm of cells; contain a variety of digestive enzymes.

Question 4

Define microbial antagonism.

Answer 4

When indigenous microflora prevent the establishment of arriving pathogens; competition for colonization sites, competition for nutrients, production of substances that kill other bacteria.

Question 5

Define colicin.

Answer 5

Produced by some strains of E. coli. Is a bacteriocin- proteins produced by some bacteria to kill other bacteria.

Question 6

Define bacteriocins.

Answer 6

Proteins produced by some bacteria to kill other bacteria.

Question 7

Define superinfection.

Answer 7

When antibiotics reduce or eliminate certain members of the indigenous microflora, leading to overgrowth by bacteria or fungi that are resistant to the antibiotics being administered.

Question 8

Define pyrogens.

Answer 8

Substance that stimulate the production of fever; may originate either outside or inside the body.

Question 9

Define interferon.

Answer 9

Small, antiviral proteins produced by virus-infected cells. They “interfere” with viral replication.

Question 10

Define complement cascade.

Answer 10

When the proteins of the complement system (complement components) interact with each other.
Consequences:
-Initiation and amplification of inflammation
-Attraction of phagocytes to sites where they are needed (chemotaxis)
-Activation of leukocytes
-Lysis of bacteria and other foreign cells
-Increased phagocytosis by phagocytic cells (opsonization)

Question 11

Define complement.

Answer 11

A group of approximately 30 different proteins (including nine proteins- C1 through C9) that are found in normal blood plasma.

Question 12

Define opsonization.

Answer 12

A process by which phagocytosis is facilitated by the deposition of opsonins (antibodies or certain complement fragments) onto the surface of particles or cells.

Question 13

Define inflammation.

Answer 13

The body’s normal response to any local injury, irritation, microbial invasion, or bacterial toxin by a series of events; vasodilation, increased permeability of the capillaries, and escape of leukocytes from the capillaries.

Question 14

Define vasodilation.

Answer 14

An increase in the diameter of the capillaries, which increases blood flow to the site.

Question 15

Define phagocytosis.

Answer 15

The process by which phagocytes surround and engulf (ingest) foreign material.

Question 16

Define chemotaxis.

Answer 16

The directed migration of phagocytes caused by chemicals called chemotactic agents.

Question 17

Describe the 1st line of defense.

Answer 17

1st line of defense- skin and mucous membranes as physical barriers, cellular and chemical factors (dryness, acidity, mucous (traps pathogens and contains toxic substances- lysozyme, lactoferrin, and lactoperoxidase)), and microbial antagonism.

Question 18

Describe the second line of defense.

Answer 18

1) Transferrin- a glycoprotein synthesized in the liver that sequesters iron, depriving pathogens of this essential nutrient
2) Fever- stimulates WBCs to deploy and destroy invaders, reduces available plasma iron, induces production of IL-1 (Interleukin 1), which causes the proliferation, maturation, and activation of lymphocytes in the immune response.
3) Interferons- small, antiviral proteins produced by virus-infected cells which interfere with virus replication.
4) The complement system- the interaction among complement components that aid in immune response
5) Inflammation- vasodilatation, increased permeability of the capillaries, & escape of leukocytes from the capillaries
6) Phagocytosis- when phagocytes surround and engulf foreign material

Question 19

Describe the third line of defense.

Answer 19

Antibodies are usually produced in the body in response to the presence of foreign substances- antigens. They are very specific- only recognize and attach to one antigen that stimulated it’s production.

Question 20

What is meant by “nonspecific host defense mechanisms” and how do they differ from “specific host defense mechanisms”?

Answer 20

Nonspecific- ways in which the body attempts to destroy all types of substances that are foreign to it, including pathogens.
Specific- immune responses that are specific to the antigen that stimulated it.

Question 21

Describe 3 ways in which the digestive system is protected from pathogens.

Answer 21

1) digestive enzymes
2) acidity of the stomach (pH 1.5)
3) alkalinity of the intestines

Question 22

Describe how interferons function as host defense mechanisms.

Answer 22

They are produced by a virus-infected cell, they are released, and they attach to membranes of surrounding cells and prevent viral replication from occurring in those cells. This the spread of infection is inhibited.

Question 23

Name 3 cellular and chemical responses to microbial invasion.

Answer 23

1) increased production of transferrin- to bind to free plasma iron.
2) production of Interleukin 1 (IL-1)- a pyrogen- to stimulate the production of fever. IL-1 causes the proliferation, maturation, and activation of lymphocytes.
3) inflammation- localized infection, prevents spread of invaders, neutralizes toxins, and aids in the repair of damaged tissues.

Question 24

Describe the major benefits of complement activation.

Answer 24

1) initiation and amplification of inflammation
2) attraction of phagocytes to sites where they are needed
3) activation of leukocytes
4) lysis of bacteria and other foreign cells
5) increased phagocytosis by phagocytic cells

Question 25

List 4 main signs and symptoms associated with inflammation.

Answer 25

1) redness
2) heat
3) swelling (edema)
4) pain

Question 26

Discuss the 4 primary purposes of the inflammatory response.

Answer 26

1) localize infection
2) prevent the spread of microbial invaders
3) neutralize any toxins being produced at the site
4) aid in the repair of damaged tissue

Question 27

Describe the 4 steps in phagocytosis.

Answer 27

1) chemotaxis- the directed migration of phagocytes, caused by chemicals called chemotactic agents produced by cells called chemokines
2) attachment- phagocytes can only ingest objects to which they can attach- sometimes opsonization is necessary to coat the particle with opsonins for the phagocyte to attach to
3) ingestion- particle becomes surrounded by the membrane of the phagocyte and ingested
4) digestion- phagosome fuses with a nearby lysosome to form a digestive vacuole (phagolysosome) within which killing and digestion occur

Question 28

Identify the 3 major categories of leukocytes.

Answer 28

1) monocytes
2) lymphocytes
3) granulocytes

Question 29

List the 3 categories of granulocytes.

Answer 29

1) basophils- not phagocytes, contain histamine a and other chemical mediators
2) eosinophils- causes of high concentrations are allergies and helminth infections
3) neutrophils- mush more efficient at phagocytosis than eosinophils

Question 30

State ways that pathogens escape destruction by phagocytes.

Answer 30

1) some bacteria produce leukocidin- an enzyme that kills phagocytes
2) waxes in the cell of some bacteria protect them from digestion
3) some bacteria are able to live and multiply within phagocytes
4) some bacteria are able to prevent the fusion of lysosomes with phagosomes

Question 31

Categorize the disorders and conditions that affect the body’s nonspecific host mechanisms.

Answer 31

1) Leukopenia- low number of leukocytes from bone marrow injury from radiation, drugs, nutritional deficiencies, congenital stem cell defects
2) disorders and conditions affecting leukocyte motility and chemotaxis
3) disorders and conditions affecting intracellular killing by phagocytes
4) nutritional status
5) increased iron levels
6) stress
7) age
8) cancer and chemotherapy
9) AIDS
10) drugs
11) genetic defects