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SECTION 11.4 The Immune System
A pathogen is any microorganism which can infect and possibly kill the infected organism. Pathogens include
bacteria, viruses, and fungi. These organisms can be found in air, water, and food.
The immune system is the system of the body which prevents and resists the infection of pathogens.
Non-Specific Defences
The 1st line of defence
physical barriers -> skin, nose and ear hair, mucus membranes, cilia of trachea, tears, sweat, saliva, urine
chemical barriers -> stomach acid, sweat, tears, saliva, skin oil
Cells - Cells such as neutrophils, monocytes, and macrophages digest all pathogens if they get inside the body. They are
not fussy eaters.
The 2nd Line of Defence is the ________________ due to the presence of ______________attacking the cells of the
body. As the body cells are under attack, ____________________ at the site release _______________which increases
blood flow to the area and attracts phagocytes (__________________________________________). Macrophages are
giant white blood cells which develop from monocytes and ingest large amounts of pathogens and damaged tissue. Due
to the increased blood flow, the site of inflammation has certain symptoms such as redness, warmth, swelling, and pain
(pinching of nerves).
Pus forms which consists of live and dead pathogens, dead white blood cells, and body fluid. The pus will drain from the
body or be reabsorbed by the body.
If the pathogen is a virus, infected cells will release the ________________________________ which will cause
neighboring cells to create enzymes to prevent viral reproduction.
The 3rd Line of Defence is the immune response which uses the macrophages and lymphocytes to attack and
destroy foreign material in the body. The system is based on the presence of ____________________which are proteins
or carbohydrates on the cell membranes of foreign cells.
Antigens indicate to the immune system that these cells do not belong.
Cells Involved in the Immune Response:
Macrophages (monocytes)
Lymphocytes - two main types of lymphocytes:
 
T-lymphocytes & B-lymphocytes
T cells -> T-cells, helper T-cells, killer T-cells, memory T-cells, suppressor T-cells
T cells - mature in thymus gland
T cells: function - cellular immunity; controls both cellular and antibody immunities
B cells -> B-cells, plasma cells, memory B-cells
B cells - mature in bone marrow
B cells: function - antibody immunity
Functions of Each Cell Type
Macrophages
T-cells
Helper T-cells
Killer T-cells have receptors on their cell membranes which will bind to the antigen on the viral infected cells and cause
them to rupture.
Memory T-cells
Suppressor T-cells shut down the killer T-cells and will slow down antibody production by plasma cells when the
pathogens are brought under control.
B-cells
Plasma cells.
Memory B-cells
Types of Immunity
Active Immunity is a type of acquired immunity in which the body produces its own antibodies to attack a foreign
antigen.
Passive Immunity is a type of immunity in which the body is given antibodies from the blood of another
person or animal.
Immune System Disorders
Acquired Immune Deficiency Syndrome
Allergies
 Allergies is a disorder due to the rapid over-reaction to an antigen which is normally not harmful.
-> e.g. insect bites, nuts, flower pollen
Histamine?????
Anaphylaxsis????
Autoimmune disorders
Cancer