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Your Magic Doctor
Your Magic Doctor
How Does Immune System Work?
How Does Immune System Work?
Barriers Keep the Invaders Out!
Barriers Keep the Invaders Out!
Barriers: Skin, mucous, and hairs work together to keep invaders out! The first line of defense is the skin, which is rich in antibodies (Traps).
Barriers keep germs out!
If invaders get past the skin, they need to get by nonspecific defenses like the Macrophages, Natural Killer cells, and complement proteins.
Antigens: Identifying Marks
Antigens: Identifying Marks
These logos identify brands, just like antigens identify enemy invaders.
Antigens: a code, a symbol, or a mark that triggers an immune response. An antigen is like a fingerprint. Tissue from another person carries foreign antigens. Identical twins, however, have identical antigens.
Phagocytes - The Eating Cells
Phagocytes - The Eating Cells
If invaders get past the barriers, they will soon be detected by Macrophages.
A macrophage is a phagocyte, or eating cell. Macrophage means "big eater."
Macrophages are like a Pacman because it gobbles up germs.
Macrophages are found in all tissues and act as housekeepers, guards, and frontline defenders. They are scavengers. They are garbage collectors. They are voracious eaters and will eat the enemy as well as dead body cells.
Macrophage
Macrophage
Scanning electron micrograph of human macrophage (Gray blob) ingesting Streptococcus pyogenes.
Macrophage
Macrophage
(The bacteria are orange.) The spherical cell riding piggyback on the macrophage is a lymphocyte, an important component in the immune response to infection.
Macrophages place antigens of enemies on its MHC to warn Helper T cells that the body is under attack. The MHC is like a flagpole that displays parts of the invaders (Antigens).
After doing this, the macrophages and Helper T cells reproduce and go to war.
Helper-T Cells: The Generals
Helper-T Cells: The Generals
Macrophages will communicate with the Helper-T Cells which are in command. Helper-T cells are like generals because they identify the enemy and command the other cells in the immune system to go to war.
Helper-T cells are also known as the CD4T Cells. They look at the antigen's epitopes (specific antigenic information) to identify the invader.
The helper T cell then communicates with phagocytes, B cells, and killer T cells and it commands them to replicate and go to war.
The Helper T cell is also known as a CD4 T Cell. It is the leader of the immune system.
B-Cells: Make Antibodies (Traps)
B-Cells: Make Antibodies (Traps)
The y-shaped antibodies stick to germs. These antibody traps slow down invaders and make them visible to other team members of the immune system.
This is a model of a typical antibody. Antibodies slow down invaders and flag them for destruction.
B cells complete maturation in bones. They are later found in Lymph nodes and become "plasma cells."
Antibodies are produced by B-cells that stick to invaders. Antibodies are like traps. Invaders that are flagged or trapped by antibodies are then eaten by phagocytes like macrophages.
B Cells become Plasma Cells: Once stimulated, the B cells replicate and turn into plasma cells that produce chemical antibodies at a rate of 10,000 molecules per second per cell! B cells (plasma cells) are found in lymph nodes. (Lymph nodes are found in your neck, armpits, and groin.)
Macrophages and Helper T cells can alert B cells to go to war. B cells complete maturation in bones and then move to the Lymph nodes. Each B cell is pre-programmed to make one specific antibody.
Lymph Nodes: Battle Arenas
Lymph Nodes: Battle Arenas
Major battles take place at Lymph nodes. Lymph nodes are like fighting arenas because battles occur there.
They are found throughout the body: neck, armpits, and groin. B cells and T cells wait for invaders there and go to war. A swollen gland is a sign that a battle is raging in the lymph node. Lymphocytes can travel in blood vessels or lymphatic vessels. Lymph is a clear fluid that bathes the body's tissues.
White blood cells fight in arenas called lymph nodes.
Your immune system fights off invaders at lymph nodes.
Antibodies: Traps
Antibodies: Traps
Antibodies: Antibodies belong to a family of large molecules known as immunoglobulins. Each has about a dozen parts and is designed for a specific invader.
They float throughout the body and wait for invaders. They are like traps.
Antibodies lock on to the antigen of the invader like a key fits into a lock. They neutralize the enemy and tag it for attack. Antibodies are like guided missiles, handcuffs, straight jackets, mines, or bear traps.
Antibodies hold invaders until Macrophages can eat them up.
Killer T Cells - Special Forces
Killer T Cells - Special Forces
Killer T Cells: Copies of Helper T cells will also deploy killer T cells.
Killer T cells destroy cells in the body that have been invaded by foreign organisms. These cells inject enzymes that eat away the infected cell. Killer T cells also destroy cancer cells. These cells are also known as CD8 Cytotoxic T Cells.
Natural Killer Cells: There are also natural killer cells. They are always on alert and they can kill any foe. Like the killer T, it kills on contact.
Killer T cells actually destroy your own body cells that have been invaded by viruses.
T Cells Go To School in the Thymus
T Cells Go To School in the Thymus
The thymus is like a nursery or a school.
T cells mature in the thymus: The thymus is an organ that is found near the heart. "T" stands for thymus.
The thymus is like a school.
When The Enemy Has Been Vanquished
When The Enemy Has Been Vanquished
Suppressor T Cells: Once the war is over and the body has won, the Suppressor T Cell slows down or stops the activities of B cells and other T cells.
Supressor T
Memory T Cells
Memory T Cells
Memory T Cell: T and B cells, generated during the initial infection, stay behind and become memory cells.
Memory cells stay on the lookout for future invaders. If the same invader tries to invade the body a second time, an overwhelming attack is mounted by these memory cells, and the new invasion is quickly crushed.
The body is now immune to that particular organism. This mechanism allows vaccinations to work.
Your body can fight off future infections faster because memory T cells remember what to do.
More Information:
More Information:
Classifying Leukocytes
Classifying Leukocytes
Agranulocytes
Agranulocytes
White blood cells (Leukocytes) can be classified as follows:
White blood cells (Leukocytes) can be classified as follows:
a. Neutrophil
b. Eosinophil
c. Basophil
Agranulocytes
a. Lymphocyte (B or T cell)
b. Monocyte (Precursor to Macrophage)
Trauma, bacteria and dirt signal to white cells in nearby vessels there is damage to control. Neutrophils, the most active and phagocytic of the white blood cells, become sticky and begin to adhere to the inside of the vessel wall. Adherence slows the cells down, making them "roll" on the inside of the vessel. The neutrophils then become super-adherent and squeeze out between endothelial cells that line the vessel; a phenomenon called "diapedesis". (Taken From Cells Alive!) From there, the white cells must FIND, EAT, and KILL foreign microbes.
Every tissue in the body is loaded with capillaries, small blood vessels slightly larger than red blood cells. Coursing through the capillaries you find blood plasma transporting nutrients to the tissue and removing waste. Red cells slip by single file releasing their load of oxygen and picking up carbon dioxide for return to the lungs. Lymphocytes can travel in blood vessels or lymphatic vessels. Lymph is a clear fluid that bathes the body's tissues. (Taken From Cells Alive!)
Complement proteins: Complement proteins float throughout the body. They can work with antibody to create holes in invaders. They inject liquid into an invader and cause it to pop.
Lymphokines: These are chemicals that cells use to communicate with one another. Lymphokines start the replication process. For instance, after exchanging these chemicals and replicating, copies of the macrophages and helper T cells rush to the spleen and lymphnodes where they stimulate the production of other cells to fight the invader. The spleen filters antigens from the blood. Lymphocytes, including both T cells and B cells, secrete lymphokines, while monocytes and macrophages secrete monokines.
MHC: MHC stands for "major histocompatibility complex". MHC is like the flag on a ship. It is found on the surface of all cells. It signals the body that the cell is friendly. (It is important for the body to distinguish self and non-self.) MHC can also signal an alarm if a virus is reproducing in the cell.
B cells can also place foreign antigens on their MHC and alert the Helper T cells.
Phagocytes: Phagocyte means, "eating cell", or "cell eater". Phagocytes include monocytes, macrophages, and neutrophils. Phage = eat. Cyte = cell.
The monocytes are phagocytes that circulate in the blood. When monocytes migrate to tissues, they become macrophages. Special macrophages can be found in the lungs, kidney, brain, and liver. Neutrophils are similar to macrophages, but smaller.
Influenza - Worldwide Pandemic
In 1918-1919, the influenza pandemic occurred. 20 million people died worldwide! Influenza is a mutation-prone RNA virus and it underwent an antigenic shift that year; it changed so much that human immune systems could not recognize the virus. Pigs, ducks, chickens are mixing vessels for the viruses.
Influenza Virus
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