Chapter 39 Immunity from Disease

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Chapter 39 Immunity from Disease
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What Youll Learn

• You will describe how infections are transmitted
  and what causes the symptoms of diseases.
• You will explain the various types of innate and
  acquired immune responses.
• You will compare antibody and cellular immunity

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• Section Objectives
• Describe how pathogens are transmitted.
• Explain what causes the symptoms of a disease.

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What is an infectious disease?

• Disease-producing agents such as bacteria,
  protozoans, fungi, viruses, and other parasites
  are called pathogens. (NOT all microorganisms
  are pathogens
• main sources of pathogens are soil, contaminated
  water, and infected animals, including other
  people.

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Reservoirs of pathogens
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Transmission of disease

• Pathogens can be transmitted to a host from
  reservoirs in four main ways by direct contact,
  by an object, through the air, or by an
  intermediate organism called a vector.

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Transmission of disease II

• The common cold, influenza, and STDs are spread
  by direct contact.

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Transmission of disease III

• Bacteria and other microorganisms can be present
  on nonliving objects such as money, toys, or
  towels.
• Transmission occurs when people unknowingly
  handle contaminated objects.

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Transmission of disease IV

• Airborne transmission of a disease can occur when
  a person coughs or sneezes, spreading pathogens
  contained in droplets of mucus into the air.

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Transmission of disease V

• Diseases transmitted by vectors are most commonly
  spread by insects and arthropods
• malaria and the West Nile virus are transmitted
  by mosquitoes.
• Lyme disease and Rocky Mountain spotted fever are
  diseases that are transmitted by ticks.
• Flies also are significant vectors of disease.

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What causes the symptoms of a disease?

• When a pathogen invades your body, it encounters
  your immune system.
• If the pathogen overcomes the defenses of your
  immune system, it can metabolize and multiply,
  causing damage to the tissues it has invaded, and
  even killing host cells

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Damage to the host by viruses and bacteria

• Most of the damage done to host cells by bacteria
  is inflicted by toxins.
• These poisons can inhibit protein synthesis in
  the host cell, destroy blood cells and blood
  vessels, produce fever, or cause spasms by
  disrupting the nervous system.

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Patterns of Diseases

• Some diseases, such as typhoid fever, occur only
  occasionally in the United States.
• On the other hand, many diseases are constantly
  present in the population-endemic disease. Ex.
  Common cold

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Treating Diseases

• 1 way An antibiotic is a substance produced by
  a microorganism that, in small amounts, will kill
  or inhibit the growth and reproduction of
  bacteria.
• Your body also has its own built-in defense
  system the immune system that works to keep you
  healthy.

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• Section Objectives
• Identify the cells, tissues, and organs that
  make up the immune system.
• Compare innate and acquired immune responses.
• Distinguish between antibody and cellular
  immunity.

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Innate Immunity

• The bodys earliest lines of defense against
  any and all pathogens make up your nonspecific,
  innate immunity.

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Nonspecific defense I

• 1st line of defense
• Skin Intact skin is a formidable physical barrier
  to the entrance of microorganisms
• Body secretions mucus traps many microorganisms
• Sweat, tears, and saliva all contain the enzyme
  lysozyme, which is capable of breaking down the
  cell walls of some bacteria

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Nonspecific defense II

• 2nd line of defense
• Inflammation(Inflammatory response) characterized
  by four symptomsredness, swelling, pain, and
  heat histamine released causes blood vessels in
  the injured area to dilate,(redness) which makes
  them more permeable to tissue fluid. Fluid that
  leaks from the vessels helps the body destroy
  toxic agents and restore homeostasis (swelling
  and pain,heat)

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Nonspecific defense III

• 2nd line of defense
• Phagocytosis of pathogens white blood cells that
  destroy pathogens by surrounding and engulfing
  them.
• Macrophages are white blood cells that provide
  the first defense against pathogens that have
  managed to enter the tissues.

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Nonspecific defense IV

• Phagocytosis of pathogens
• If the infection is not stopped by the tissue
  macrophages, another type of phagocyte, called
  a neutrophil is attracted to the site.
• If the infection is not stopped by tissue
  macrophages and neutrophils - Monocytes

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Nonspecific defense V
Swelling occurs
Tissue fluid moves into injured area

• After a few days, infected tissue harbors a
  collection of live and dead white blood cells,
  multiplying and dead pathogens, and body fluids
  called pus.
• Pus formation usually continues until the
  infection subsides.
• Eventually, the pus is cleared away by
  macrophages.

Pus
Phagocytes
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Nonspecific defense VI

• Protective proteins
• Interferons are proteins that protect cells from
  viruses.
• Complement help attract phagocytes to foreign
  cells and help destroy foreign cells
• Natural Killer cellstype of white blood cell
  that destroy the body's own infected cells, may
  attack cells that form tumors

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Acquired Immunity

• Defending against a specific pathogen by
  gradually building up a resistance to it
• This acquired immune response enables these
  white blood cells to inactivate or destroy the
  pathogen.
• Acquired immunity involves the production of two
  kinds of immune responses antibody immunity and
  cellular immunity

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Acquired Immunity

• SPECIFIC IMMUNITY
• IMMUNE RESPONSE
• a recognition system that distinguishes self
  from non-self
• responds to foreign molecules called antigens
• Stimulates the body to make antibodies
• specific defensive proteins which help to
  counter antigens in various ways

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The lymphatic system

• The lymphatic system becomes a crucial
  battleground during infection
• a network of lymphatic vessels and organs
• It returns tissue fluid to the circulatory system
• It fights infections
• Lymph nodes are key sites for fighting infection
• They are packed with lymphocytes and macrophages

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Lymphocytes type of white blood cell that carry
out the immune response
B lymphocyte

• Two kinds
• B cells secrete antibodies that attack antigens
  (antibody immunity)
• T cells attack cells infected with pathogens
  (cellular immunity)

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Antibody Immunity

• Triggered by a specific antigen, a B cell
  differentiates into a plasma cell
• -The plasma cell secretes antibodies
• (see handout.)

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Antibody Immunity

• An antibody molecule has antigen-binding sites
  specific to the antigen
• Do not posses the power to destroy antigens
  directly, tag and mark them for destruction by a
  variety of mechanisms

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Cellular Immunity
Infected cells
Perforin
Pathogen engulfed by
Foreign antigen
Infected cell lyses
Macrophage
Cytotoxic T cell
Displays antigens on surface and stimulates T cell
Attacks infected cell
Stimulates Cytotoxic T cell
Helper T cell
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Passive and Active Immunity

• Acquired immunity to a disease may be either
  passive or active.

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Passive Immunity

• Passive short term, antibodies passed on, not
  stimulated by antigens,
• acquired naturally by placenta or breast milk or
• artificially acquired by a shot

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Active Immunity

• Active long term, conferred by actual encounter
  with infection (naturally acquired) or
  vaccination (artificially acquired)
• vaccine substance consisting of
  weakened, dead, ,or parts of pathogen or antigen
  that when injected , stimulates the immune system

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DISORDERS OF THE IMMUNE SYSTEM

• Allergies are overreactions to certain
  environmental antigens called
• allergens Ex. Animal dander, dust mites,
  pollen
• release of histamine causes symptoms
  sneezing, increased mucus production in the
  nasal passages, and redness.
• Antihistamines can relieve symptoms

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DISORDERS OF THE IMMUNE SYSTEM

• Autoimmune diseases
• immune system also can mistakenly attack the
  bodys own tissues
• Examples Rheumatic fever, Type I Diabetes,
  Multiple Sclerosis, Rheumatoid arthritis, Lupus

Rheumatoid arthritis
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DISORDERS OF THE IMMUNE SYSTEM
HIV on a lymphocyte

• Immunodeficiency diseases
• Immune components are lacking, and infections
  recur
• Ex Acquired immune deficiency syndrome (AIDS)
• SCIDS

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AIDS

• HIV (Human Immunodeficiency Virus) the virus
  that causes AIDS
• HIV is transmitted mainly in blood and semen
• HIV kills helper T-cells and leads to AIDS

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• T cells and antibodies also can attack
  transplanted tissue, such as a transplanted
  kidney, that comes from a source outside the
  body.