Immune System
Structures in the system
Lymph vessels and nodes
Spleen
Tonsils
Bone marrow
Thymus gland
Lymphocytes/leukocytes (white blood cells)
Non-specific immunity
1st line of defense: skin and mucous membranes
–Forms a protective barrier against all types of pathogens (disease causing agents)
–Cilia, mucous, tears, saliva, enzymes are extra layers of protection
2nd line of defense: inflammatory response
–Injured cells release histamine which causes dilation of capillaries allowing them to
leak fluids
–Phagocytes also move out of capillaries to the site of injury and attack invaders
–Local temperature rises to slow down pathogen reproduction
–Antihistamines prevent dilation of capillaries
Specific immunity
Recognizes and destroys a particular pathogen
Pathogens are recognized by their antigens—”flags” that stick out of their cell
membrane
Causes an immune response which uses the white blood cells and lymphatic system to
fight the invader
Primary immune response
Initiated by recognition of an invader (a non-self antigen)
–Antigen binds to receptors
–Lymphocytes against this antigen are produced
–Lymphocytes secrete antibodies
–Pathogen is destroyed
–Memory cells remain to give immunity to this pathogen
Types of lymphocytes (all blood cells are produced in the bone marrow)
B cells: mature in bone marrow and produce antibodies (proteins that attach to antigens)
T cells: mature in the thymus gland
–Cytotoxic T cells: kill infected host cells
–Helper T cells: help B cells make antibodies; are activated by dendritic cells displaying
the antigen
–Suppresser T cells: turn off B cells as the infection is brought under control
Macrophages/phagocytes: engulf and disassemble pathogens
Antibodies (immunoglobulin proteins)
B cells make antibodies in response to antigens
Antibodies are protein chains, most of which are the same—constant regions
At the ends are variable regions—areas that change to fit the antigen of a specific
invader like a lock and key
Some
antibodies stick out of B cell membranes while others are released directly into
the blood stream
Each antibody can hold onto more than one pathogen, causing them to clump together,
which makes them easier to engulf
They signal the complement system or phagocytes to destroy the pathogens
You need 1000’s of different antibodies because there are 1000’s of different antigens
Antibody mediated response
Once the antibody and antigen have combined on a B cell it becomes activated and
produces 2 kinds of cells
Plasma cells produce 1000’s of antibody cells per second and move to the sight of
infection
Memory cells: remain in your body long after exposure which gives you immunity to
the disease on subsequent exposures (secondary immune response)
Auto-immune diseases
Self vs non-self system uses your MHC so your immune system recognizes your own
cells so they are not attacked and destroyed
In auto-immune diseases T cells are produced that kill your cells
–Lupus, rheumatoid arthritis, multiple sclerosis, scleroderma
Vaccines
Solutions made from weakened or dead pathogens or their antigens
Causes antibodies to form without making you sick
Production of antibodies gives you active immunity; can last for the rest of your life
Being given antibodies produced by someone else gives you passive immunity; only
lasts a short time
Human Blood Type
ABO Blood type
Blood Groups and Transfusions
Antibodies to non-self blood types exist in the body
Transfusion with incompatible blood leads to agglutination and destruction of the
transfused cells