chapter 35

Question 1

immunity

Answer 1

The human body has the ability to resist almost all types
of organisms or toxins that tend to damage the tissues
and organs. This capability is called immunity

Question 2

acquired immunity

Answer 2

that does not develop
until after the body is first attacked by a bacterium,
virus, or toxin; often weeks or months are required
for the immunity to develop

Question 3

This innate immunity makes the human body resistant

to

Answer 3

paralytic viral infections of
animals, hog cholera, cattle plague, and distemper—a viral disease that kills a large percentage of dogs that
become afflicted with it

Question 4

humoral immunity or

B-cell immunity

Answer 4

the body develops
circulating antibodies, which are globulin molecules in
the blood plasma capable of attacking the invading agent.
This type of immunity is called humoral immunity or
B-cell immunity

Question 5

cell-mediated immunity or T-cell immunity

Answer 5

The second type of acquired immunity is
achieved through formation of large numbers of activated
T lymphocytes that are specifically crafted in the lymph
nodes to destroy the foreign agent. This type of immunity
is called cell-mediated immunity or T-cell immunity

Question 6

both type of lymphocytes are derived from

Answer 6

multipotent hematopoietic stem cells that form common lymphoid progenitor cells.

Question 7

The Thymus Gland Preprocesses the T Lymphocytes.

Answer 7

The T lymphocytes, after origination in the bone marrow, first migrate to the thymus gland. Here they divide rapidly and at the same time develop extreme diversity for reacting against different specific antigens. That is, one thymic
lymphocyte develops specific reactivity against one antigen, and then the next lymphocyte develops specificity against another antigen. This process continues until there are thousands of different types of thymic lymphocytes with specific reactivities against many thousands of
different antigens

Question 8

a clone

of lymphocytes.

Answer 8

All the different lymphocytes that are capable of
forming one specific antibody or T cell are called a clone
of lymphocytes

Question 9

Role of Macrophages in the Activation

Answer 9

Most invading organisms are first phagocytized and partially digested by the macrophages, and the antigenic
products are liberated into the macrophage cytosol. The macrophages then pass these antigens by cell-to-cell
contact directly to the lymphocytes, thus leading to activation of the specified lymphocytic clones. The macrophages, in addition, secrete a special activating substance,
interleukin-1, that promotes still further growth and
reproduction of the specific lymphocytes.

Question 10

Role of the T Cells in Activation of the B Lymphocytes

Answer 10

Some of the T cells that are
formed, called T-helper cells, secrete specific substances
(collectively called lymphokines) that activate the specific
B lymphocytes. Indeed, without the aid of these T-helper
cells, the quantity of antibodies formed by the B lymphocytes is usually slight.

Question 11

Formation of Antibodies by Plasma Cells.

Answer 11

Before exposure to a specific antigen, the clones of B lymphocytes remain dormant in the lymphoid tissue. Upon entry
of a foreign antigen, macrophages in lymphoid tissue phagocytize the antigen and then present it to adjacent
B lymphocytes. In addition, the antigen is presented to T cells at the same time, and activated T-helper cells are formed. These helper cells also contribute to extreme activation of the B lymphocytes, as discussed later. The B lymphocytes specific for the antigen immediately enlarge and take on the appearance of lymphoblasts. Some of the lymphoblasts further differentiate to form
plasmablasts, which are precursors of plasma cells. In the plasmablasts, the cytoplasm expands and the rough endoplasmic reticulum vastly proliferates. The plasmablasts then begin to divide at a rate of about once every 10 hours
for about nine divisions, giving in 4 days a total population of about 500 cells for each original plasmablast. The mature plasma cell then produces gamma globulin antibodies at an extremely rapid rate—about 2000 molecules per second for each plasma cell

Question 12

formation of memory cells

Answer 12

A few of the lymphoblasts formed by activation of a clone
of B lymphocytes do not go on to form plasma cells but
instead form moderate numbers of new B lymphocytes similar to those of the original clone. In other words, the B-cell population of the specifically activated clone becomes greatly enhanced, and the new B lymphocytes are added to the original lymphocytes of the same clone. They also circulate throughout the body to populate all the lymphoid tissue; immunologically, however, they remain dormant until activated once again by a new
quantity of the same antigen. These lymphocytes are called memory cells

Question 13

what gives antigen its specificity

Answer 13

the structural organization of amino acids in the variable chain of antibody

Question 14

5 classes of antibodies

Answer 14

IgM IgG IgE IgD IgE

Question 15

MOST important immunoglobins of body

Answer 15

IgG which constitute 75% of antibodies in body are bivalent
IgE which constitute a small percentage but are involved in allergic reactions
IgM are made during primary response and have 10 binding sites so they play a major role

Question 16

mechanism of action of antibody is done by two ways

Answer 16

direct attack

or by activation of complement system

Question 17

direct attack is done by

Answer 17

1. Agglutination, in which multiple large particles with antigens on their surfaces, such as bacteria or
   red cells, are bound together into a clump
2. Precipitation, in which the molecular complex of soluble antigen (such as tetanus toxin) and antibody
   becomes so large that it is rendered insoluble and precipitates
3. Neutralization, in which the antibodies cover the toxic sites of the antigenic agent
4. Lysis, in which some potent antibodies are occasionally capable of directly attacking membranes of cellular agents and thereby cause rupture of
   the agent

Question 18

main function of compliment system

Answer 18

is to enhance the function of antibodies and phagocytic cells to destroy pathogens neutralize and remove damaged cells and promote inflammation

Question 19

classical pathway

Answer 19

The classical pathway is initiated by
an antigen-antibody reaction. That is, when an antibody binds with an antigen, a specific reactive site on the “constant” portion of the antibody becomes uncovered, or “activated,” and this in turn binds directly with the C1 molecule of the complement system, setting into motion
a “cascade” of sequential reactions,
beginning with activation of the proenzyme C1. The C1 enzymes that are formed then activate successively increasing quantities of enzymes in the later stages of the
system so that from a small beginning, an extremely large “amplified” reaction occurs

Question 20

t lymphocytes react to antigen only

Answer 20

when they are bound to specific proteins called as MHC proteins on the surface of antigen presenting cells

Question 21

what are antigen presenting cells

Answer 21

macrophages, b lymphocytes and dendritic cells

Question 22

what does MHC protein do

Answer 22

they bind with peptide fragments of antigen that have been degraded inside the antigen presenting cells and then transport them to the cell surface

Question 23

There are two types of MHC proteins:

Answer 23

MHC I proteins, which present antigens to cytotoxic T cells, and
(2) MHC II proteins, which present antigens to T-helper cells.

Question 24

t helper cells serves as a major regulator how

Answer 24

they release lymphokines which are protein mediators which act on other cells of immune system and bone marrow

Question 25

HIV affects what cells

Answer 25

helper T cells

Question 26

B-cell stimulating factor are

Answer 26

interleukin 4, 5, 6 which have a affect on b cell response

Question 27

helper t cells affect on macrophages

Answer 27

First, they slow orstop the migration of the macrophages after they have been chemotactically attracted into the inflamed tissue area, thus causing great accumulation of macrophages. Second, they activate the macrophages to cause far more efficient phagocytosis, allowing them to attack and destroy increasing numbers of invading bacteria or other tissue destroying agents.

Question 28

what lymphokine has a direct positive feedback on stimulating activation t helper cells

Answer 28

interleukin 2

Question 29

cytotoxic c cells

Answer 29

The receptor proteins on the surfaces of the cytotoxic cells cause them to bind tightly to the organisms or cells that contain the appropriate binding-specific antigen. After binding, the cytotoxic T cell secretes hole-forming proteins, called perforins, that literally punch round holes in the membrane of the attacked cell. Then fluid flows rapidly into the cell from the interstitial space. In addition, the cytotoxic T cell releases cytotoxic substances directly into the attacked cell. Almost immediately, the attacked cell becomes greatly swollen, and it usually dissolves shortly thereafter.

Question 30

autoimmune disease

Answer 30

(1) rheumatic fever, in which the body becomes immunized against tissues in the joints and heart, especially the heart valves, after exposure to a specific type of streptococcal toxin that has an epitope in its molecular structure similar to the structure of some of the body’s own self-antigens; (2) one type of glomerulonephritis, in which the person becomes immunized against the basement membranes of glomeruli; (3) myasthenia gravis, in which immunity develops against the acetylcholine receptor proteins of the neuromuscular junction, causing paralysis; and (4) systemic lupus erythematosus (SLE), in which the person becomes immunized against many different body tissues at the same time, a disease that causes extensive damage and even death when SLE is severe.

Question 31

first type of immunization

Answer 31

is done by injecting the body with a dead organism that is no longer capable of causing disease ( typhoid fever, whooping cough, diphtheria, and other bacterial diseases)

Question 32

2nd type of immunization

Answer 32

injecting toxins that have been treated by chemicals so their toxicity is destroyed but still have the antigens on them for immunization ( tetanus, botulism, similar toxic disease)

Question 33

3rd type of immunization

Answer 33

And, finally, a person can be immunized by being infected with live organisms that have been “attenuated.” That is, these organisms either have been grown in special culture media or have been passed through a series of animals until they have mutated enough that they will not cause disease but do still carry specific antigens required for immunization. This procedure is used to protect against smallpox, yellow fever, poliomyelitis, measles, and many other viral diseases.

Question 34

passive immunity

Answer 34

transfusion of antibody or t cells from another human or animal for immunity is called as passive immunity

Question 35

delayed reaction allergy is caused by

Answer 35

T cells

Question 36

Anaphylaxis.

Answer 36

When a specific allergen is injected directly into the circulation, the allergen can react with basophils of the blood and mast cells in the tissues located immediately outside the small blood vessels if the basophils and mast cells have been sensitized by attachment of IgE reagins. Therefore, a widespread allergic reaction occurs throughout the vascular system and closely associated tissues. This reaction is called anaphylaxis. Histamine is released into the circulation and causes body-wide vasodilation, as well as increased permeability of the capillaries with resultant marked loss of plasma from the circulation. Occasionally, a person who experiences this reaction dies of circulatory shock within a few minutes unless treated with epinephrine to oppose the effects of the histamine. Also released from the activated basophils and mast cells is a mixture of leukotrienes called slow-reacting substance of anaphylaxis. These leukotrienes can cause spasm of the smooth muscle of the bronchioles, eliciting an asthma-like attack, sometimes causing death by suffocation.

Question 37

Urticaria.

Answer 37

Urticaria results from antigen entering specific skin areas and causing localized anaphylactoid reactions. Histamine released locally causes (1) vasodilation that induces an immediate red flare and (2) increased local permeability of the capillaries that leads to local circumscribed areas of swelling of the skin within another few minutes. The swellings are commonly called hives. Administration of antihistamine drugs to a person before exposure will prevent the hives.

Question 38

Hay Fever

Answer 38

In hay fever, the allergen-reagin reaction occurs in the nose. Histamine released in response to the reaction causes local intranasal vascular dilation, with resultant increased capillary pressure and increased capillary permeability. Both these effects cause rapid fluid leakage into the nasal cavities and into associated deeper tissues of the nose, and the nasal linings become swollen and secretory. Here again, use of antihistamine drugs can prevent this swelling reaction. However, other products of the allergen-reagin reaction can still cause irritation of the nose, eliciting the typical sneezing syndrome.