Chapter 16: Specific Host Defense Mechanisms: An Introduction To Immunology

Question 0

Define immunity.

Answer 0

Condition of being immune. When someone is resistant to certain infectious diseases they are immune, which is a result of the immune response.

Question 1

Define immunology.

Answer 1

The scientific study of the immune system and immune responses.

Question 2

Define antigenic determinant.

Answer 2

Individual molecules or antigenic sites that stimulate the production of antibodies.

Question 3

Define immunoglobulins.

Answer 3

Globular glycoproteins in the blood that participate in immune reactions- the term antibodies is used to refer to immunoglobulins with particular specificity for an antigen.

Question 4

Define primary response.

Answer 4

The initial response to an antigen. It takes about 10-14 days for antibodies to be produced. When the antigen is used up, the number of antibodies in the blood declines as the plasma cells die.

Question 5

Define secondary response.

Answer 5

The increased production of antibodies after the second exposure to the antigen (e.g., a booster shot).

Question 6

Define agammaglobulinemia.

Answer 6

The condition when a person lacks the ability to produce antibodies.

Question 7

Define hypogammaglobulinemia.

Answer 7

The condition when a person produces too few antibodies.

Question 8

Define T cell.

Answer 8

T lymphocytes- one type of cell that has a major role in immune responses. The 2 major types of T cells are: helper T cells (T-helper cells/Th cells/CD4+ cells)- who’s primary function is to secrete cytokines(chemicals for cellular communication) and cytotoxic T cells (Tc cells, CD8+ cells)- who’s primary function is to destroy virally infected host cells, foreign cells, and tumor cells.

Question 9

Define B cells.

Answer 9

B lymphocytes- another type of cells that has a major role in immune Responses. B cells are antibody producing cells that are activated by antigens.

Question 10

Define plasma cell.

Answer 10

The cells that secrete antibodies; they are derived from B cells.

Question 11

Define immunosuppression.

Answer 11

The condition when a person’s immune system is not functioning properly. Can be acquired or inherited.

Question 12

Differentiate between humoral and cell-mediated immunity (CMI).

Answer 12

Humoral immunity always involves the production of antibodies in response to antigens. After their production, these humoral (circulating) antibodies remain in the body where they protect against the specific pathogens that stimulated their production.
CMI involves various cell types, with antibodies only playing a minor role if at all. Antibodies are unable to enter cells, so CMI is capable of controlling chronic infections by intracellular pathogens.

Question 13

Distinguish between active acquired immunity and passive acquired immunity.

Answer 13

Active- immunity that results from the active production or receipt of protective antibodies during ones lifetime.
Passive- a person receives antibodies that were produced by another person, rather than producing them, usually only temporary.

Question 14

Distinguish between natural active acquired immunity and artificial active acquired immunity and give examples.

Answer 14

Naturally acquired- acquired in response to the entry of a live pathogen into the body in response to an actual infection- May be permanent or temporary
Artificially acquired- when a person receives a vaccine- stimulates a person’s immune system to produce specific protective antibodies

Question 15

Distinguish between natural passive acquired immunity and artificial passive acquired immunity and give examples.

Answer 15

Natural- antibodies present in the mothers blood cross the placenta when in utero or given to baby after birth in colostrum
Artificial- the transfer of antibodies from an immune person to a susceptible person- hyperimmune serum globulin is prepared from the serum of persons with high antibody levels against certain diseases

Question 16

Outline the steps involved in the processing of T-independent antigens and T-dependent antigens.

Answer 16

T-independent- 1) processing of T-independent antigens is initiated when an appropriate B cell makes physical contact with the free antigenic determinant 2) the activated B cell undergoes extensive cell division, producing a clone of identical B cells 3) some of the members of the newly formed clone mature into antibody-producing plasma cells and others become memory cells.
T-dependent- 1) after invasion of the body, an antigen is ingested and digested by a macrophage 2) within the macrophage, antigenic determinants of the bacterial cell attach to molecules called major histocompatibility complex (MHC) molecules 3) the combined AP-MHC molecules are displayed on the surface of the macrophage; at this point, the macrophage is referred to as an antigen-presenting cell (APC) 4) a T-helper cell attaches to one of the AP-MHC MOLECULES, divides, and secretes cytokines(chemical signals) 5) when cytokines reach a B cell that is capable of recognizing that particular signal, the activated B cell divides, producing a clone of identical B cells 6) some of the members of the newly formed clone mature into antibody-producing plasma cells. Antibodies are expelled rapidly for several days until the plasma cell dies. Each plasma cell makes only one type of antibody; one that will bind with the antigenic determinant that activated the B cell and stimulated production of that antibody. Members of the clone that do not become plasma cells, and some of the activated T cells, remain in the body as memory cells, able to respond very quickly should the antigen enter the body at a later date

Question 17

Identify the 2 primary functions of the immune system.

Answer 17

1) to differentiate between “self” and “nonself”

2) to destroy that which is nonself

Question 18

Describe a monomeric antibody molecule.

Answer 18

Resembles a Y. Consists of 2 identical light polypeptide chains (at the top of the Y), 2 identical heavy polypeptide chains, 2 antigen-binding sites (at the top of the Y), and a Fc region (at the base of the Y)

Question 19

Identify and describe the 5 immunoglobulin classes (isotypes).

Answer 19

IgA- the predominant immunoglobulin in saliva, tears, seminal fluid, colostrum, breast milk, and mucus secretions. Can exist as a monomer or a dimer (2 monomers held together by a J-chain)
IgD- found in large quantities on the surface of B cells- function unknown. Exists as a monomer
IgE- in atopic people, produced in response to allergens. Found on the surface of basophils and mast cells. Exists as a monomer
IgG- the only class of immunoglobulin that can cross the placenta- help protect newborns during the first months of life. Can bind to a wide range of cellular receptors to promote phagocytosis and antibody-dependent cytotoxicity. High levels of IgG are produced very rapidly during the secondary response to antigens. They are long-lived, sometimes lasting for the lifetime of the person. Exists as a monomer (the lightest of the immunoglobulins)
IgM- can potentially bind to 10 identical antigenic determinants. IgM antibodies are the first antibodies formed in the primary response to antigens (including pathogens), although IgG antibodies later become the most prevalent class. IgM antibodies are relatively short lived, remaining in the bloodstream for only a few months. It's too big to cross the placenta. Provides protection in the earliest stages of infection. Exists as a pentamer, 5 monomers held together by a J-chain; the largest of the immunoglobulins.

Question 20

List the types of cells that are killed by natural killer cells (NK) cells

Answer 20

Target cells-

1) foreign cells
2) host cells infected with viruses or bacteria
3) tumor cells

Question 21

Name the 4 types of hypersensitivity reactions

Answer 21

Immediate-type hypersensitivity reactions (occur from within a few minutes to 24 hours after contact with a particular antigen):
1) Type I hypersensitivity reactions- anaphylactic reactions (allergic reactions)
2)Type II hypersensitivity reactions- cytotoxic reactions (involve damage to or death of body cells)
3)Type III hypersensitivity reactions- immune complex reactions (damage to tissues and organs is initiated by antigen- antibody complexes)
Delayed-type hypersensitivity (DTH) reactions (take up to 24-48 hours or longer to manifest):
4)Type IV hypersensitivity reactions- also known as cell-mediated reactions; antibodies play only a minor role, if any; an example is a positive TB skin test

Question 22

Outline the steps involved in allergic reactions, starting with the initial sensitization to an allergen and ending with the typical symptoms of an allergic reaction.

Answer 22

IgE antibodies are produced in response to the persons first exposure to the allergen and bind to the surface of basophils and mast cells. Degranulation of the basophils and mast cells occurs during subsequent exposure to the allergen, when allergen binds to these IgE antibodies; outpouring granules and their irritating and damaging contents (chemical mediators). These mediators include histamines, prostaglandins, serotonin, bradykinin, slow-reacting substances of anaphylaxis (SRS-A), leukotrienes, and chemicals that attract eosinophils. Reactions can either be localized or systemic. Hay fever, asthma, and hives are localized anaphylaxis. Allergens entering through the digestive tract can result in hives, vomiting, and diarrhea. Systemic anaphylaxis can lead to anaphylactic shock, which, if untreated, can lead to death. Symptoms include flushing of the skin with itching, headache, facial swelling, and difficulty breathing; this is followed by falling blood pressure, nausea, vomiting, abdominal cramps, and urination.

Question 23

Cite 6 examples of allergens.

Answer 23

1) animal dander
2) drugs (e.g., penicillin)
3) foods (e.g., peanuts, shellfish, dairy products)
4) house dust (dust-mite feces)
5) insect venom
6) latex
7) mold spores
8) pollens

Question 24

List 5 possible explanations for a positive tuberculosis (TB) skin test.

Answer 24

1) the person has active tuberculosis
2) the person had tuberculosis at one time and recovered
3) the person was infected with M. tuberculosis at one time but the organisms were killed by that persons host defense mechanisms
4) the person currently harbors live M. tuberculosis organisms but does not actually have tuberculosis
5) the person had received Bacillus Calmette-Guerin (BCG) vaccine at one time