Human Disease and Immune System

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Human Disease and Immune System
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Disease

• Any change, other than injury, that interferes
  with the normal functioning of the body

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Infectious Disease

• Produced by pathogens
• pathogens disease causing microorganisms
• Results when pathogen begins to injure cells and
  tissue

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Infection

• When a pathogen has successfully invaded the body
• Not all infections produce disease

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Methods of Transmission/Spread of Infectious
Disease

• Direct contact with infected person Airborne
• Coughing, Sneezing Droplets in air
• Direct contact with secretions of infected person
  
• ex. blood, (blood transfusions, contaminated
  needles, cuts/wounds)
• ex. Sexual contact
• Contact with infected animals (ex. ticks,
  mosquito)
• Contaminated water or food

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Bacteria

• Most harmless
• Infect tissues directly
• Produces toxins (poisons)
• Ex. botulism (s.n. Clostridium botulinum)
• Attacks nervous system often fatal

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Bacteria cont.

• Some grow in living cells
• Ex. Ricketsias
• Ticks-Rocky Mountain Spotted-Fever
• Typhus- by lice or fleas

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Fungi

• Molds, mushrooms
• Most do not cause disease
• Fungal infections
• Many caused by dermophytes
• Ex. Athletes foot, ringworm
• Not limited to skin can be internal
• Ex. San Joaquin Valley Fever

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Protozoan

• 30 different species can cause human disease
• Many in tropical regions
• Ex. Malaria (Plasmodium)
• Lives in bloodstream
• Spread by mosquitoes

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Protozoan cont.

• Ex. Amebic dysentery (Entamoeba histolytica)
• Affects intestineabdominal pain and fever
• Contaminated water

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Protozoan cont.

• Ex. African Sleeping sickness (Trypanosoma)
• Spread by tsetse fly
• Tropics in Africa
• Inflammation of nervous system
• Usually fatal

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Virus

• Non-cellular particles invade living cells
• Have genetic info---RNA or DNA
• No lifelike activity until infect living cells

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Virus

• Attaches to cell structure
• Inserts genetic material
• May lie dormant or act immediately

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Virus

• Examples
• HIV causes AIDS (Acquired Immune Deficiency
  Syndrome
• Poliomyelitis causes Polio
• Variola causes Smallpox
• Measles

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Virus
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Virus
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Kochs Postulates
Suspected pathogen
No pathogen
Suspected pathogen
The pathogen should always be found in the body
of a sick organism and should not be found in a
healthy one.
The pathogen must be isolated and grown in the
laboratory in a pure culture.
Suspected pathogen grown in pure culture.
Dead mouse
Dead mouse
Healthy mouse
Injection of organisms from pure culture
Pathogen
When purified pathogens are placed in a new host,
they should cause the same disease that infected
the host.
The very same pathogen should be reisolated from
the second host. And it should be the same as
the original pathogen.
Dead mouse
Healthy mouse
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Immune Response

• The bodys reaction against a foreign substance
• Nonspecific Defense
• Specific Defense

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Nonspecific Defense

• Acts against all disease-causing organisms in the
  same way regardless of the biological nature of
  the organism

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Nonspecific Defense cont.

• 1st line of defense
• Skin prevents entry of pathogen
• Mucustraps pathogens
• Sweat and oil produce acidic environment that
  kills bacteria
• Secretions (i.e. mucus, sweat, saliva,
  tears)-contain enzymes that kill bacteria

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Nonspecific Defense cont.

• 2nd line of defense Inflammatory response
• White blood cells enter infected area
• Phagocytesengulf and destroy bacteria
• Macrophages large engulf 100s of bacteria
• Neutrophils smaller engulf small s of bacteria

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 The Inflammatory Response
Wound
Skin
Phagocytes move into the area and engulf the
bacteria and cell debris
Bacteria enter the wound
Capillary
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Specific Defense.

• Immune response
• Antigen Substance that triggers an immune
  response
• Humoral Immunity
• Cell-Mediated Immunity
• Permanent Immunity

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Primary and SecondaryImmune Responses
Interval between exposures
First exposure
Second exposure
Antibody Concentration
Time
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 Structure of an Antibody
Antigen-binding sites
Antigen
Antibody
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Humoral Immunity

• Immunity against pathogens in body fluids (blood
  lymph)
• Antibody basic functional unit of humoral immune
  response

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 Humoral Immunity
Bacterial antigens also stimulate B cells
Bacteria With Antigens on Surface
B cell
Helper T cell assists the activated B cell to
develop into an antibody-producing plasma cell
Active B cells proliferate to produce clones of
memory cells
A large phagocyte called a macrophage engulfs a
bacterium
Plasma cell produces large amounts of antibody
proteins, released intothe bloodstream
T cell binds to activated macrophage
T cell, activated by macrophage, becomes a helper
T cell
T cell
Macrophage
Antigens are displayed on surface of macrofage
after digestion of bacterium
Circulating antibodies bind to bacterial
antigens, helping other immune cells to identify
and destroy bacteria
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Cell-MediatedImmune Response
Helper T cell activates killer T cells and B
cells
Macrophage
T cell binds to activated macrophage
Helper T Cell
Killer T Cell
T Cell
T cell, activated by macrophage, becomes a helper
T cell
Antigens are displayed on surface of macrophage
Infected Cell
Killer T cells bind to infected cells, disrupting
their cell membranes and destroying them
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Permanent Immunity

• Once a body has been exposed to a pathogen,
  memory B T cells remain capable of producing
  specific antibodies to that pathogen.

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Active Immunity

• Edward Jenner (cowpox, smallpox)
• Vaccination (Vacca cow)
• Injection of weakened or mild form of pathogen
• Produces active immunity
• Body has ability to initiate immediate active
  immune response
• Body makes its own antibodies

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Passive Immunity

• Last short time
• Antibodies produced by other animals injected
  into the bloodstream
• Antibodies produce passive immunity
• Ex. Travelers, Maternal immunity

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Immune System Disorders

• Allergies
• Autoimmune Disease

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What Are Allergies?

• Ahhhhchoo! Do you or someone you know have
  allergies? As you know, the immune system
  protects the body against invading pathogens.
  Sometimes, however, the immune system can make a
  mistake. Allergies occur when the immune system
  overreacts to an antigen, a substance that
  triggers an immune response.

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Allergies

• Overreaction of immune system
• Antigens bind to mast cells
• Mast cells release histamines
• Histamines increase blood flow fluids
• Take antihistamines to counteract allergies

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Autoimmune

• Immune system makes a mistake and attacks the
  bodys own cells.
• Ex Streptococcusif not treated can cause
  Rheumatic fever (atttacks/scars lining of heart)
• Ex. Juvenile-onset diabetes (attacks insulin
  producing cells of pancreas)

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Autoimmune cont.

• Multiple sclerosis (MS)
• Destruction of myelin sheath surrounding nerve
  fibers
• AIDS (Acquired Immune Deficiency Syndrome)