THE BODY’S DEFENSES

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CHAPTER 43 THE BODYS DEFENSES
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The Nature of Disease

• Pathogenic Organisms
• Genetic Disorders
• Toxic Chemicals
• Other Environmental Factors
• Physical Damage to Organs
• Nutritional Disorders

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Types of Pathogenic Organisms

• Viruses
• Bacteria
• Protozoan
• Fungi
• Animal
• Parasites

4
Mechanisms of Disease by Pathogens

• Utilization of host nutritional resources
• Physical damage to host tissues
• Production of toxic substances
• Chromosomal and gene damage
• Body cells behave abnormally

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Viruses
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Bacteria
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Defense Mechanisms

• External defense
• Internal Defense
• Immune Defense

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1st Line of Defense

• Skin acts as barrier to microbes and viruses
• - sweat has a low pH
• Mucus traps foreign particles
• Tears
• - Lysozyme has antimicrobial action
• Gastric stomach acid

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Body Coverings The Skin
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Body Coverings Mucous Membranes
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2nd Line of Defense

• Phagocytic cells (WBCs)
• N L M E B
• Natural Killer (NK) Cells attack virus infected
  cells
• Inflammatory Response
• Antimicrobial proteins
• Lysozyme
• Interferon
• Antibodies

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Nonspecific Phagocytosis
Neutrophils Monocytes Eosinophils
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Mechanism of Phagocytosis
Mechanism of Phagocytosis
Macrophage
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Lymphatic System
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Inflammatory Response
Histamine prostaglandins released
Capillaries dilate Clotting begins
Chemotactic factors attract phagocytic cells
Phagocytes consume pathogens cell debris
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Characteristics of Immunity

• Recognition of self versus non-self
• Response is specific
• Retains a memory allowing an accelerated second
  response
• Can respond to many different materials
• Involves lymphocytes and antibodies

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Types of Immunity

• Active Immunity
• Naturally-Acquired Active Immunity
• Artificially-Acquired Active Immunity
• Passive Immunity
• Naturally-Acquired Passive Immunity
• Artificially-Acquired Passive Immunity

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Types of Acquired Immunity
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Active Immunity

• The production of antibodies against a specific
  disease by the immune system.
• Naturally acquired through disease
• Artificially acquired through vaccination
• Vaccines include inactivated toxins, killed
  microbes, parts of microbes, and viable but
  weakened microbes.
• Active immunity is usually permanent

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• A vaccinated person has a secondary response
  based on memory cells when encountering the
  specific pathogen.
• Routine immunization against infectious diseases
  such as measles and whooping cough, and has led
  to the eradication of smallpox, a viral disease.
• Unfortunately, not all infectious agents are
  easily managed by vaccination.
• HIV vaccine in the works

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Passive Immunity

• Passive Immunity- Protection against disease
  through antibodies produced by another human
  being or animal.
• Effective, but temporary
• Ex. Maternal antibodies
• Colostrum.

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• Passive immunity can be transferred artificially
  by injecting antibodies from an animal that is
  already immune to a disease into another animal.
• Rabies treatment injection with antibodies
  against rabies virus that are both passive
  immunizations (the immediate fight) and active
  immunizations (longer term defense).

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Immune System Response to Antigens

• Humoral Immunity
• Involves antibodies (secreted from B cells)
  dissolved in the blood plasma.
• Demonstrated as a immune response using only the
  blood serum.
• Defense against bacteria, bacterial toxins,
  viruses.

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Immune System Response to Antigens

• Cell-Mediated Immunity
• Involves the activities of specific white blood
  cells (T cells).
• Defense against cancer cells, virus-infected
  cells, fungi, animal parasites, foreign cells
  from transplants.

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Lymphocyte Formation
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B Cells

• Mature in bone marrow
• Involved in humoral immunity
• Once activated by antigen, proliferate into two
  clones of cells plasma cells that secrete
  antibodies and memory cells that may be converted
  into plasma cells at a later time

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B Cells
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B Cells
B Cells
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Activation of B Cells by Antigen
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Clonal Selection
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Clonal Selection
plasma cells
memory cells
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Humoral Immune Response
first exposure to antigen A
antibody concentration
time (days)
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Humoral Immune Response
first exposure to antigen A
primary response concentration of anti-A antibody
antibody concentration
second exposure to antigen A
time (days)
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Humoral Immune Response
antibody concentration
time (days)
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Humoral Immune Response
primary response concentration of anti-B antibody
antibody concentration
time (days)
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• Antibodies constitute a group of globular serum
  proteins called immunoglobins (Igs).
• A typical antibody molecule has two identical
  antigen-binding sites specific for the epitope
  that provokes its production.

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Antibody Molecule
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Mechanisms on Antibody Action

• Precipitation of soluble antigens
• Agglutination of foreign cells
• Neutralization
• Enhanced phagocytosis
• Complement activation leading to cell lysis
• Stimulates inflammation

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• The binding of antibodies to antigens to form
  antigen-antibody complexes is the basis of
  several antigen disposal mechanisms.

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The classical complimentary pathway, resulting in
lysis of a target cell
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Immunoglobin Classes

• IgM
• 1st response to antigen
• Effective in agglutination
• Cant cross placenta

• IgD
• B cell activation
• Cant cross placenta

• IgG
• Most common form
• Crosses blood vessels
• Crosses placenta (passive immunity to fetus)

• IgE
• Histamine reactions and allergies

• IgA
• Secreted from mucus membranes
• Prevents attachment of bacteria to epithelial
  surface
• In colostrum

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Overview of Immune System Responses
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T Cells

• Mature in thymus
• Involved in cell-mediated immunity
• Activated when another cell presents antigen to
  them
• Several types of T cells cytoxic T cells, helper
  T cells, suppressor T cells, and memory T cells

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T Cells

• There are two main types of T cells, and each
  responds to one class of MHC molecule.
• Cytotoxic T cells (TC) have antigen receptors
  that bind to protein fragments displayed by the
  bodys class I MHC molecules.
• Helper T cells (TH) have receptors that bind to
  peptides displayed by the bodys class II MHC
  molecules.

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Cytotoxic T Cell
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Helper T Cells
interleukin 1
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The central role of helper T cells
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• The central role in Helper T cells in an infected
  cell

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T-Independent vs T-Dependent Antigens
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• T-independent antigens
• T cells activated by binding to certain antigens
• No memory cells generated
• Weaker response than t-dependent
• T-dependent antigens
• Most antigens require co-stimulation to evoke a
  B-cell response
• Antibody production stimulated with help from TH
• Most antigens are t-dependent

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• T-dependent antigens- can trigger a humoral
  immune response by B cells only with the
  participation of helper T cells.

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Tissue/Organ Transplants

• Major Histocomatibility Complex (MHC)
• Bone marrow
• Organs

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Abnormal immune function can lead to disease

• Malfunctions of the immune system can produce
  effects ranging from the minor inconvenience of
  some allergies to the serious and often fatal
  consequences of certain autoimmune and
  immunodeficiency diseases.

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Abnormal Immune Function

• Autoimmune Disease
• Allergy
• Immunodeficiency

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Autoimmune Disease

• Rheumatoid arthritis
• Type I Diabetes
• MS
• Lupis
• Crohns disease
• Graves disease

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ABO Blood Types
Phenotype Genotype O i i A I A I A or I A
i B I B I B or I B i AB I A I B
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Type A
ABO Blood Types
b
b
Produces anti-B antibodies
b
b
b
b
b
b
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Type B
ABO Blood Types
a
a
a
Produces anti-A antibodies
a
a
a
a
a
a
a
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Type AB
ABO Blood Types
Produces neither anti-A nor anti-B antibodies
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Type O
ABO Blood Types
b
a
b
a
a
Produces both anti-A and anti-B antibodies
b
a
b
a
a
b
a
b
a
a
a
b
b
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Rh Factor and Pregnancy
RH indicates protein
RH- indicates no protein
15 of population is RH-
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Rh Factor and Pregnancy
Rh mother w/Rh- baby no problem Rh- mother
w/Rh baby problem Rh- mother w/Rh- father no
problem Rh- mother w/Rh- baby-- no problem
RhoGAM used _at_ 28 weeks
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Allergy (Immune Hypersensitivity)

• Hypersensitive response to certain environmental
  allergens
• Food, pollen, pet dander, asthma, bee sting
• Anaphylactic shock
• - epinephrine

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• Mast cells, IgE, and the allergic response.

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Problems
AIDS
Acquired Immunodeficiency Syndrome HIV (virus)
attacks T-cells Weakens or eliminates immune
system Susceptible to many fatal diseases
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• Transmission of HIV requires the transfer of body
  fluids containing infected cells, such as semen
  or blood, from person to person.
• Unprotected sex
• Nonsterile needles
• HIV transmission among heterosexuals is rapidly
  increasing as a result of unprotected sex with
  infected partners.
• HIV in Africa and Asia- primarily by heterosexual
  sex

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AIDS

• In 1983, a retrovirus, now called human
  immunodeficiency virus (HIV), had been identified
  as the causative agent of AIDS.

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• With the AIDS mortality close to 100, HIV is the
  most lethal pathogen ever encountered.
• Molecular studies reveal that the virus probably
  evolved from another HIV-like virus in
  chimpanzees in central Africa and appeared in
  humans sometimes between 1915 and 1940.
• These first rare cases of infection and AIDS went
  unrecognized.

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AIDS
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AIDS
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• HIV Testing
• The HIV antibody test has be used to screen all
  blood supplies in the U.S. since 1985.
• May take weeks or months before anti-HIV
  antibodies become detectable.
• Drug treatment available
• Best prevention is education and protected sex