1. 39.2 Defense Against Infectious Disease
CH. 39 Immune System
39.2 Defense Against Infectious Disease

2. Infectious Diseases
Pathogen: Disease producing agents such as bacteria, protozoan's, fungi, viruses, and other parasites.
Infectious Disease: Any disease caused by the presence of pathogens in the body.
Innate Immunity: Non-specific earliest lines of the bodies defense.
Acquired Immunity: Defense against a specific pathogen by gradually building up a resistance.

3. Innate Immunity First barrier of innate immunity is the skin.
Mucus & oils: Keep surface areas from drying out and capture antigens.
sweat, saliva and tears: contain an enzyme called lysozyme that breaks down the walls of some bacteria.

4. Inflammatory Response
Basophils and Mast cells release Histamine which calls in the Phagocytes and dilates blood vessels.
This results in the heat, redness, pain and swelling of the area.

5. Phagocytosis Phagocytes are cells that engulf (eat) particles.
They include Macrophages (found in tissues), Eosinophils and Nuetrophils (circulate in the blood stream).
Macrophages are the first defense INSIDE the body.
They digest pathogens and/or infected or damaged cells.
Pus: Made up of live and dead white blood cells, multiplying and dead pathogens and body fluids.

6. Acquired Immunity
Antigen: foreign substances that stimulate an immune response.
Antibodies: Proteins in the blood that correspond specifically to certain antigens.
Lymphatic System: A network of vessels and nodes that filter the tissue fluids (lymph) of the body looking for antigens.

7. Lymphatic System
Fluid travels (in one direction only) through lymph vessels to lymph nodes.
Lymph nodes contain lymphocytes, white blood cells that defend the body against antigens.
Tonsils, the spleen, & Thymus are all part of the lymphatic system.

8. Lymphocytes
T Cell: A type of lymphocyte that is produced in the bone marrow.
Helper T Cells: Pass the message (Antigen) onto B cells. (Mature in the Thymus) – Antibody immunity
Killer T Cells: Are specific for a single antigen, they go to the antigen and release enzymes directly into them to kill them. (Mature in spleen, tonsils and lymph nodes) – Cellular immunity
B Cell: lymphocyte that when activited by a Helper T cell becomes a plasma cell and produces antibodies, or become memory B cells which store the information and provide immunity to the specific pathogen. –Antibody immunity

10. Ch. 39 Immune System
39.1 The Nature of Disease

11. Finding the Cause of a Disease
Disease:  any condition that impairs normal function, and is therefore associated with dysfunction of normal homeostasis.
Not all diseases are caused by a pathogen, some diseases are:
genetic
develop due to wear and tear on the body
caused by malnutrition
caused by exposure to toxic chemicals
are dysfunctions of the immune system itself (autoimmune diseases/disorders)

12. Reservoirs of Pathogens
For a disease to continue to spread there must be a continual source of the disease causing organism. (A reservoir or source)
The main source of human disease pathogens is the human body.
Carriers: People who carry a pathogen but show no signs of infection.
Incubation Period: The time frame in which a person has contracted a pathogen but is unaware because they show no symptoms of disease.

13. Non-human Reservoirs
Animals: Some disease can be transmitted from animals to humans.
Flu, Rabies, Lyme disease and the black plague
The major non-living reservoirs are soil and water.
Soil can carry bacteria, fungi and parasites that can transmit to humans.
Contaminated water can contain bacteria. (Many historical cholera outbreaks were caused by drinking water contaminated by feces.

14. What Causes the Symptoms of Disease
Fever: May be triggered by a toxin released by a bacteria or can even be triggered by a chemical released by some white blood cells.
Although a high fever can be dangerous or even fatal, a low grade fever can help to fight off infection by increasing the body temperature to a degree unsuitable for the invading bacteria.
Pain: from inflammation, and/or the death of infected cells.
Sneeze: Irritation of the mucous membrane in the nasal cavity that results in a release of histamine that triggers a sneeze to expel the irritant.
Cough: Similar to a sneeze but when the mucous membrane in the lungs is irritated.

15. Patterns of Disease
Endemic: a disease that is constantly present in the population.
The Common Cold
Epidemic: Many people inflicted with the same disease in a given area.

16. Allergies
Allergens are antigens that do not cause disease. They trigger an immune response which results in the symptoms (sneezing, itching, inflammation), but pose no threat to the body. It is an overreaction of the immune system.

17. Darn those Mast Cells!!!
Allergens trigger B cells to release a certain kind of antibody called IgE.
This triggers Mast Cells to release histamine which causes inflammation resulting in symptoms.
Anti-histamines interfere with Histamine and provide temporary relief.

18. Anaphylactic Shock
An especially dangerous and severe form of allergic reaction as sometimes seen with bee sting or peanut allergies.
In these cases mast cells release inflammatory chemicals very suddenly.
Resulting in dangerously low blood pressure (due to dilation of blood vessels), and severe inflammation.
Epinephrine (Epipen) : Used to treat anaphylactic shock but only works short term. It temporarily raises blood pressure and relaxes the smooth muscles of the airway.

19. Autoimmune Diseases
When the immune system goes wacko and turns against certain cells within the body.
The immune system for some reason begins to see certain cells as “invaders” and no longer sees them as “self”.
Examples : Lupus, Multiple Sclerosis, Rheumatoid Arthritis, Insulin Dependant and Diabetes (Type I).