The Body’s Defenses

I. Nonspecific Defenses Against Infection

 The skin and mucous membranes provide first-line barriers to infection.

 Phagocytic cells, inflammation, and antimicrobial proteins function early in infection.

II. How Specific Immunity Arises

 Lymphocytes provide the specificity and diversity of the immune system

 Antigens interact with specific lymphocytes, inducing immune responses and immunological memory.

 Lymphocyte development gives rise to and immune system that distinguishes self from nonself.

III. Immune responses

Helper T lymphocytes function in both humoral and cell-mediated immunity:an overview

In the cell-mediated response, cytotoxic T cells counter intracellular pathogens: a closer look

In the humoral response, B cells make antibodies against extracellular pathogens: a closer look

Invertebrates have a rudimentary immune system

IV. Immunity in Health and Disease

Immunity can be achieved naturally or artificially

The immune system’s capacity to distinguish self from nonself limits blood transfusion and tissue transplantation

Abnormal immune function can lead to disease

AIDS is an immunodeficiency disease caused by a virus.

Chapter 43 The Immune System

Overview: Reconnaissance, Recognition, and Response

• An animal must defend itself against unwelcomed intruders—the many potentially dangerous viruses, bacteria, and other pathogens it encounters in the air, in food, and in water.

• Two major kinds of defense have evolved to counter these threats.

The first kind of defense is innate immunity

• A second kind of defense is acquired immunity.

Concept 43.1 Innate immunity provides broad defenses against infection

• An invading microbe must penetrate the external barrier formed by the skin and mucous membranes, which cover the surface and line the openings of an animal’s body.

The skin and mucous membrane provide first-line barriers to infection.

Phagocytic cells and antimicrobial proteins function early in infection.

Concept 43.2 In acquired immunity, lymphocytes provide specific defenses against infection

• While microorganisms are under assault by phagocytic cells, the inflammatory response, and antimicrobial proteins, they inevitably encounter lymphocytes, the key cells of acquired immunity, the body’s second major kind of defense.

Lymphocytes provide the specificity and diversity of the immune system.

Lymphocyte development gives rise to an immune system that distinguishes self from nonself.

Antigens interact with specific lymphocytes, inducing immune responses and immunological memory.

Concept 43.3 Humoral and cell-mediated immunity defend against different types of threats

Helper T lymphocytes function in both humoral and cell-mediated immunity.

In the cell-mediated response, cytotoxic T cells counter intracellular pathogens.

In the humoral response, B cells make antibodies against extracellular pathogens.

Immunity can be achieved naturally or artificially.

Concept 43.4 The immune system’s ability to distinguish self from nonself limits tissue transplantation

• In addition to attacking pathogens, the immune system will also attack cells from other individuals.

Concept 43.5 Exaggerated, self-directed, or diminished immune responses can cause disease

AIDS is an immunodeficiency disease caused by a virus.

Terminology:

Non-self:
A widely used term in immunology, covering everything which is detectably different from an animal’s own constituents. Infectious micro-organisms, together with cells, organs or other materials from another animal are the most important non self substances from an immunological viewpoint, but drugs and even normal foods which are, of course, non-self too, can sometimes give rise to immunity.

Infection:
parasitic viruses, bacteria, protozoa, worms or fungi that attempt to gain access to the body or its surfaces are probably the chif raison d’etre of the immune system. Higher animals whose immune system is damaged or deficient frequently succumb to infections which normal animals overcome.

Natural resistance:
entry of many microorganisms is prevented or rapidly eliminated by aniticrobial defence mechanism. Others can avoid elimination and survive to cause disease.

Adaptive immune response:
the development or augmentation of defence mechanisms in response to a particular stimulus. Aka an infectious organism. It can result in elimination of the microorganism and recovery from disease and often leaves the host with specific memory, enabling it to respond more effectively with the same infections.

Vaccination:
a method of stimulating the adaptive immune response and generating memory and acquired resistance without suffering the full effects of the disease. The name comes from vacca – cow.

Autoimmunity:
the body’s own cells and molecules do not normally stimulate its adaptive immune responses because of a variety of special mechanisms which ensure a state of self tolerance, but in certain circumstances they do stimulate a response and the body is attacked by its own self.

NATURAL IMMUNITY

Interferon A family of proteins produced rapidly by many cells in response to virus infection, which block the replication of virus in other cells.

Lysozyme An enzyme secreted by macrophages, which attacks the cell wall of some bacteria. Interferon and lysozyme are sometimes described as “natural antibiotics”

Complement A series of enzymes present in serum which when activated produce widespread inflammatory effects, as well as lysis of bacteria, etc… some bacteria activate complement directly, while others only do so with the help of antibody.

PMN Polymorphonuclear leucocyte, a short-lived ;scavenger; blood cell, whose granules contain powerful bactericidal enzymes.

MAC Macrophage, a large tissue cell responsible for removing damaged tissue, cells, bacteria, etc… both PMN;s and macrophages come from the bone marrow and are therefore known as myeloid cells.

Phagocytosis (Cell eating) Engulfment of a particle by a cell. Macrophages and PMNs (which used to be called microphages) are the most important phagocytic cells. They great majority of foreign materials entering the tissues are ultimately disposed of by this mechanism.

NK (natural killer) cell a lymphocyte-like cell capable of killing some targets, notably virus0infected cells, but without the recptor or the fine specificity characteristic of true lymphocytes.

ADAPTIVE IMMUNITY

Antigen strictly speaking, a substance that stimulates the production of antibody. The term is often applied, however, to substances that stimulate any type of adaptive immune response. Typically, antiguens are foreign (nonself) and either particulate (cells bacteria, etc…) or large protein or polysaccharide molecules. But under special conditions small molecules and even self components can become antigenic.

Specific Term used to denote the production of an immune response more or less selective for the stimulus e.g. a lymphocyte which responds to, or an antibody which “fits” a particular antigen. For example, antibody against measles virus will not work against mumps.

Antibody Serum globulins with a wide range of specificity for different antigens. Antibodies can bind to and neutralize bacterial toxins, and also, by binding to the surface of bacteria, viruses or other parasites, increase their adherence to and phagocytosis by myeloid cells. This can be even further increased by the abilisty of many antibodies to activate copmplent

HELP by T cells is required for the secretion of most antibodies by B cells. There are also “suppressor” T cells which have the opposite effect.

Chapter 43: Body’s defenses Quiz

1.An Rh-postive baby is born to an Rh-negative mother. The mother is treated with antibodies specific for the Rh factor in order to

a. protect her from an inappropriate immune response.

b.prevent her from generating memory B cells specific for the Rh factor.

c.protect her future Rh-positive babies.

d.induce an immune response to Rh antibodies.

e.both b and c

2.which of the following results in long-term immunity?

a.the passage of maternal antibodies to her developing fetus.

b. the inflammatory response to a splinter

c.the administration of serum obtained from people immune to rabies

d.the administration of the chicken pox vaccine.

e.the passage of maternal antibodies to her nursing infant

3.Which of the following is not part of the body’s nonspecific defense system?

a.natural killer (NK) cells

b.inflammation

c.phagocytosis by neutrophils

d.phagocytosis by macrophages

e.antibodies

4. Which of the following molecules is incorrectly paired with a source?

a.lysozyme-tears

b.interferons-virus-infected cells

c.interleukin-1-macrophages

d.perforins-cytotoxic T cells

e.immunoglobulins-helper T cells

5. HIV targets include all of the following except

a.macrophages

b.cytotoxic T cells

c.helper T cells

d.cells bearing CD4 and fusin

e.cells bearing CD4 and CCR5

6. Which of the following best describes the difference in the way B cells and cytotoxic T cells respond to invaders?

a.B cells confer active immunity; cytotoxic T cells confer passive immunity

b.B cells kill viruses directly; cytotoxic T cells kill virus- infected cells

c.B cells secrete antibodies against a virus; cytotoxic T cells kill virus-infected cells

d.B cells accomplish cell-mediated immunity; cytotoxic T cells accomplish humoral immunity.

e.B cells respond the first time the invader is present; cytotoxic T cells respond subsequent times.

7.Which of the following is a characteristic of the early stages of local inflammation?

a.precapillary arteriole constriction

b.fever

c.attack by cytotoxic T cells

d.release of histamine

e.antibody-complement-mediated lysis of microbes

8.An epitope associates with which part of an antibody?

a.the antibody-binding site

b.the heavy-chain constant regions only

c.the variable regions of a heavy chain and light chain combined

d.the light-chain constants region only

e.the antibody tail

9.Which of the following is not true about helper T cells?

a.they function in both cell-mediated and humoral immune responses

b.they recognize polysaccharide fragments presented by class II MHC molecules

c.they bear surface CD4 molecules

d.they are subject to HIV infection.

e.when activated they secrete IL -2 and other cytokines

10. Indicate whether each of the following choices is descriptive of a B cell, cytotoxic T cell, helper T cell, or macrophage. A single feature may be descriptive of more than one type of cell.

a.develops into an antibody-secreting plasma cell

b.is phagocytic

c.bears antigen receptors called immunoglobulins

d.bears the surface molecule CD4

e.bears the surface molecule CD8

f.is an important component of nonspecific responses

g.produces cytokines such as interleukin-2 that boost both humoral and cell-mediated responses

h.mediates specific recognition of and response to a particular antigen

i.bears surface TCR and CD3

j.kills virus-infected cells

11. Indicate whether each of the following statements is consistent or inconsistent with your understanding of immune reactions.

a.when antibodies bind to a bacterium, they directly kill it within seconds

b.autoantibodies are a normal response to one’s own biological molecules

c.complement activation

d.invertebrate immune systems can distinguish self from nonself

e.the secondary immune response is slower and weaker than the primary immune response.

f.one way that antibodies mediate the death of bacteria is by activating the complement system.

12.What is hemophagia?

13. What causes hemophagia?

14. What are the treatments for hemophagia?

By: Jenesis Burton

By attending the Summer Bridge Program, I hope to gain not only new knowledge, but also new friends, experiences, and opportunities that will enrich my college experience at the University of Houston. I hope that by joining this program I can take advantage of the scholarships, enrichment workshops, computer/study facilities, and especially the mentorship program offered by the Summer Bridge Program. By taking advantage of all of these opportunities I feel that I can reach my goal of becoming an oncologist will be ever so more in reach than if I had not had the opportunity to join this program.

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