Date post: | 13-Dec-2014 |
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Germ Theory of Disease
• “Microorganisms cause infectious disease”
• Louis Pasteur and Robert Koch did several experiments to identify disease causing agents.
• Determined that each disease is caused by a “specific” microorganism
Agents of Disease
• The following types of organisms can cause disease:1. Viruses2. Bacteria3. Protists (malaria)4. Worms 5. Fungi
• Pathogen is anything that causes disease.
Koch’s Postulates
• In order to identify what organism causes a specific disease, certain rules are followed.
• Koch Postulates:1) pathogen must be found in subject with
disease but never in a healthy subject2) pathogen can be isolated from sick person
and grown in lab3) pathogens injected into healthy person will cause the individual to become infected with the same disease4) injected pathogens can be isolated from
newly infected individual and are identical to original pathogens
Koch’s Experiment- Germ Theory
• Koch’s postulates are very important because they are the basic steps for identifying, curing, and preventing specific diseases.
What is a system?
• A group of tissues (organs) work together to do a task.
• Ex) digestive system, circulatory system, immune system…
• Function of the immune system is to protect body from invasion by pathogens.
Overview of Body’s Defenses
Non-Specific Defenses Specific Defenses
First Line of Defense Second Line of Defense
Immune Response
Skin and Mucous Inflammatory ResponseNon-SpecificWBC (phagocytes)
Specific (diverse)Antigens/AntibodiesLots WBC Memory
Non-Specific Defense• Similar to “walls of a fort” protect by keeping
pathogens out of body• Body does NOT distinguish one pathogen from
another• Your body has several non-specific defenses…
1) External- skin and mucous membranes (1st line defense)
2) Internal- Inflammatory response (2nd line defense)
“Skin”
• Physical barrier• Chemical barrier-
secretes oil and sweat (lowers pH skin), tears (contain enzyme called lysozyme), and saliva
• Sheds constantly (1 million cells per hour)
“Mucous Membranes”
• Skin contains natural openings (nose, mouth, trachea, esophagus)
• These areas are lined by mucous membranes
• Secrete mucus traps foreign objects
• Areas lined with cilia• Any pathogens make it
past, may be killed by stomach acids.
“Small Scale Infections”
• The first line of defense has been broken… second line of defense is triggered to attack any invaders present
• Inflammatory response • Body’s attempt to destroy pathogens that enter the body when the skin
is injured• Triggers series of reactions …
1.) Chemical called histamine is released from white blood cells called basophils
2) Blood vessels in area of injury swell 3) Tissue at injury site swells4) Temperature in area of injury rises = redness5) White blood cells called phagocytes move from the vessels into the injured tissue eat pathogen and damaged skin cells6) Platelets clot blood and seal infected area
“What if pathogens get in?”
• White blood cells take over and specifically identify and eliminate the pathogen.
• White blood cells = “soldiers” • Immune Response
Organs of the Immune System
White blood cells called leukocytesMade thymus and bone marrowStored tonsils, spleen, and lymph nodes.
How does your body know
there is an invader?• All pathogens have “distinct” antigens.• Antigens are marker proteins- trigger immune
response• Your body must recognize antigens in order to
identify and defeat the pathogen. • Normal cells also have antigens.
Antigen
Antibodies • Your white blood cells produce antibodies in
response to specific antigens. • These are specific to each pathogen.• All pathogens are unique, your immune system
has to prepare a specific defense against each invader.
• If you makes/have the antibodies it can kill the pathogen and you can fight the infection.
• B-cells (type of white blood cell) make the antibodies!
Building “Immunity”
• What happens if a pathogen makes it past the first lines of defense and avoids the inflammation response?
• Your body must “actively” fight the disease.
• This takes time.• This requires a special group of white
blood cells lymphocytes.
“The Soldiers”
• Many types of WBC work together during the immune response to fight the infection.
• Macrophages• Lymphocytes
“The Soldiers”
• 3 major classes of lymphocytes:
1) B-cells (plasma cells)2) T-cells
-Helper T cells -Killer T cells-Suppressor T cells
3) Memory cells
Step #1 “Invader Identification”
• Macrophages identify pathogen, eat it, display antigens, signal helper T cells (interleukin-1).
• Body temperature will increase (interleukin-1) in attempt to slow down pathogen.
• Helper T cells release interleukin 2 – signals help other leukocytes (other T-cells and B-cells)
Step #2 “Cloning Phase”
• B cells make antibodies - lock onto antigens.“Marked for death.”
Antibodies
Antigen
• Killer T cells kill infected body cells.
Step #3 “The Attack Phase”
Step #3 “The Attack Phase”
• Macrophages clean up- eating pathogens, damaged body cells, etc.
• Suppressor T cells “call off the troops” stopping the immune response.
Step #4 “Memory Phase”
• Memory cells “remember” the attack and recognize a pathogen if it re-enters body.
• Primary vs. secondary immune response
Active vs. Passive Immunity
• Active = your body must fight off the disease to build up antibodies. Ex.) Fighting an infection or Vaccination
• Passive = receiving antibodies from an outside source. Ex.) Breast feeding
Other Topics – Related to Immune System
•It is the job of the immune system to distinguish between the body’s own molecules and foreign molecules•Antigens – “marker proteins”•Blood Transfusions and Organ Transplants
If the key fits the lock = bad!!!
Blood Transfusions and the Immune System
• Blood cells have marker proteins or “antigens”
Organ Transplants and the Immune System
• Foreign organs also have marker proteins.
• If recognized as “foreign” = REJECTION.• Doctors must “match” a new organs
marker proteins to the patients.• Drugs can help suppress the immune
response (immunosuppresants).
What if the immune system fails?
• Sometimes the immune system loses the ability to distinguish itself from non-self.
• Results in autoimmune disease• Body attacks own tissues• Ex) lupus, multiple sclerosis, arthritis
LUPUS
• Person’s immune system attacks various organs or cells of the body (skin, joints, kidneys, heart, and lungs) causing damage
• Lupus is a multi-system disease because it can affect many different tissues and organs in the body.
LUPUS
Symptoms:• Fatigue • Low-grade fever, rarely exceeding 102°F• Muscle pain and joint pain or swelling• Skin rash (face, back, arms) and hair loss • Kidney problems and weight loss
Multiple Sclerosis• Immune system attacks mylein around nerve cells• Symptoms: loss ability to walk and move,
loss bladder control, paralysis and death
What if the immune system fails?
• Sometimes the immune system collapses • Ex) HIV • Virus invades macrophages and helper T
cells • Without these WBC immune response
will not work• Body becomes overwhelmed with
pathogens (HIV AIDS)
AIDS (Acquired Immune Deficiency Syndrome)
• Retrovirus (has RNA instead of DNA).• Lysogenic (stays dormant for a long
period of time).• Easily evades immune system.
1. Mutates quickly.2. Covers itself with marker proteins from
host cell (difficult to detect).
Transmission of HIV
• Four main ways1. Sexual intercourse.2. Intravenous drug use (sharing needles)3. Blood to blood contact4. Mother to child during pregnancy or
breast feeding.
What if the immune system fails?
• Sometimes the immune system overreacts thinking something is a pathogen when it is NOT
• Allergy- immune system response to a non-pathogenic antigen
• Ex) pollen, food, insect bite, dust, etc.
Steps – Allergic Reaction
• 1) Pollen inhaled• 2) cells of nasal passage
called mast cells release chemical-histamine
• 3) nearby capillaries swell- increases fluid
*Allergies are treated with medication that contains antihistamines (chemical that blocks histamine)
Immune System and Cancer
• Major function of immune system is to patrol for cancer cells
• Called Immunological Surveillance• Killer-T cells can identify, attack, and
destroy cancer cells