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Copy of Immune System
Transcript of Copy of Immune System
There are two types of immunity: natural immunity and aquired immunity.
Natural immunity is achieved when activated T and B cells become memory cells. When someone has the same antigen, they immune system is ready to destroy it.
Natural immunity is also achieved through breast milk. Babies who are nursed can receive some antibodies from their mother.
People gain acquired immunity through vaccines and serums rich in antibodies.
Mounting an Immune Response
What is the Immune System?
The immune system is a network of cells, tissues, and organs that work together to defend the body against "foreign" invaders.
These invaders include bacteria, parasites, and fungi that cause infections.
Structure of the Immune System
Organs that are associated with the immune system are called lymphoid organs because they house lymphocytes (small white blood cells).
Bone marrow (tissue in the center of bones) is the ultimate source of all blood cells (so red blood cells and lymphocytes).
The thymus is where lymphocytes (specifically T cells) mature before moving to other tissues.
The spleen functions like a lymph node.
Lymphocytes travel through blood cells and through lymphatic vessels.
the lymphatic vessels carry lymph which is a clear fluid that covers the body's tissues.
Lymph nodes are found along the lymphatic vessels. This is where immune cells congregate and encounter antigens.
B cells are one of the main types of lymphocytes.
They secrete antibodies.
Antibodies ambush foreign antigens in the bloodstream. They cannot attack infected cells.
Each B cell is programed to make one specific antibody.
When a B cell encounters an antigen that triggers it to become active, plasma cells arrive and produce antibodies.
Some examples of antibodies sare:
Immunoglobulin G (IgG): coat microbes and speed their uptake by other cells in the immune system.
IgM: Kills bacteria.
IgA: guards the entrances to the body in body fluids.
IgE: protect against parasitic infections and is responsible for allergy symptoms.
IgD: attached to the B cells and initiate early B cell responses.
Types of Immune Cells
Each immune cell is responsible for different things. Some are responsible for attacking antigens while others "memorize" them.
Immune cells include:
T cells contain receptors that see fragments of antigens on infected cells.
T cells have two important functions: they direct and regulate immune responses and they attack infected cells.
Helper T cells (Th cells) are responsible for directed and regulating immune response. They can stimulate B cells to produce antibodies, call phagocytes, and activate other T cells.
T cells destroy infected cells by binding to their targets and send chemicals trough it. Two types of attack cells are:
Cytotoxic T lymphocytes (CTLs) are the killer T cells. They attack cells that have foreign or abnormal molecules covering MCH molecules (which are the proteins that show that they are "self cells" to immune cells).
Natural Killer (NK) cells are filled with chemicals that kill infected cells. these cells recognize cells lacking MHC molecules.
Immunology and Transplants
The Immune System
T Cell Receptors
T cell receptors are molecules that are found on the surface of T cells and recognizes foreign antigens bound to self-MHC molecules on other cells.
Toll-like Receptors (TLRs) are proteins that the body uses first against microbes. they also alarm other immune cells to attack microbes.
Some are activated by molecules while others are activated by the molecules on the cell walls of bacteria.
The complement system is made up of 25 proteins working together to assist the antibodies in destroying bacteria.
This system also rid of the antigens.
Complement proteins are responsible for inflammatory responses because they cause the blood vessels to dilate.
Complement cascade: molecular cylinders are inserted to and puncture holes in the cell walls that surround the bacteria. Fluids flow into the bacteria cell causing it to swell, burst, and die.
How do they know what to attack?
The immune system can distinguish between the body's own cells (self) and foreign cells (nonself) through markers.
Nonself cells or antigens have specific markers that immune cells attack.
when the immune system mistakens self for nonself it results in an autoimmune disease (arthritis and diabetes)
Sometimes the immune system attacks harmless foreign substances like pollen. this results in an allergy. in an allergy the antigen is an allergen.
Phagocytes swallow and digest microbes and other foreign particles.
Macrophages dispose of worn-out cells and other debris in the blood. They are also response for immune response.
Dendritic cells display antigens for T cells and help stimulate T cells during an immune response.
Granulocytes contain potent chemicals that destroy microorganisms. some of the chemicals contribute to inflammation and allergy (histamine).
Neutrophil use chemicals to breakdown the microbes that they ingest.
Eosinphils and basophils "degrandulate" by spraying chemicals onto harmful cells or microbes.
these types of cell are found in the lungs, skin, tongue, and linings of the nose and intestinal tract.
Cytokines are chemical messengers that cells of the immune system use to communicate.
Some cytokines, like the interleukin 2 (IL-2) turn certain immune cell types on and off.
One group of cytokines chemically attracts specific types. They are released by cells at a site of injury or infection and call other immune cells to help repair the damage or attack an invader.
Research Frontiers in Immunology
Scientists that study the immune system can have an enormous impact on medicine, agriculture, and industry.
Monoclonal antibodies are promising treatments for a range of diseases.
Genetic Engineering allows scientist to take genes from one organism and combine them with genes of a second organism.
Through genetic engineering scientis can manufactor proteins from infectious agents for vaccines. Maybe this allows humans to become immune to different viruses while having less shots.
SCIDS can be treated by giving the patient a genetically engineered version of the missing gene.
Scientists hope to remove cancer-fighting lymphocytes from the cancer patient's tumor.
Disorders of the Immune System
Pathogens must get into the body my first moving past the skin or cell lining of the internal passages.
The skin is a barrier to microbes and is only penetrable through cuts or abrasions.
In the digestive system the stomach contains a strong acid that destroys many pathogens swallowed with food.
Microbes that enter the nose causes the nasal surfaces to secrete more mucus. Any microbe that attempts to enter the nose or lungs trigger a sneeze or cough.
Bacteria, Viruses, and Parasites
Bacteria, viruses, and parasites are the most common diseas-causing microbes.
Bacteria general live in spaces between the cells, so they are usually attacked by antibodies.
Viruses must enter cells to survive, so T cells must destroy any infected cells.
Parasites live inside or outside of the cells. intracellular parasites trigger t cell repsonses. Extracellular parasites are larger than bacter and viruses and require a bigger attack.
Immune tolerance is the tendency of T or B cells to ignore the body's own tissue.
Tolerance prevents the immune system from attack its own cells.
There are two ways tolerance occurs: central tolerance and peripheral tolerance.
Central tolerance: immune cells are exposed to many self molecules in the body during development.
Peripheral tolerance: lymphocytes recognize a self molecule but cannot respond because there are no chemical signals required to activate the T or B cells.
Immune Complex Diseases
Immune Deficiency Disorders
Allergic Diseases occurs when the immune system responds to a false alarm.
A normally harmless material is mistaken for a treat and is attacked. The response is the reason for the symptoms.
In an autoimmune disease the immune system's recognition breaks down and the body begins to create T cells and antibodies that are directed against self antigens.
For example: a form of diabetes results when T cells attack certain cells in the pancreas.
Unfortunately researchers don't know what causes an autoimmune disease.
Immune complexes are clusters of interlocking antigens and antibodies.
they are usually removed form the bloodstream, but they sometimes get trapped in the kidneys, lungs, skin, joints, or blood vessels causing inflammation and tissue damage.
Some examples are malaria, viral hepatitis, and many autoimmune diseases.
Immune dficiency disorders result from a missing part in the immune system.
These disorders can be inherited, acquired through infection or produced as a side of effect by medications.
They can be temporary.
Some examples are AIDS and SCID.
Aids is caused by the HIV virus, which destroy T cells.
SCID is when infants are born lacking all of the major immune defenses.
For transplants to be successful the body's immune system against foreign tissue must be overridden.
To avoid rejection is to ensure that the donor's tissue are as similar as possible to the recipient.
Another way to avoid a rejection is to dull the recipient's immune system through immunosuppressive drugs (like Cyclosporine A) or by using antibodies that attack mature T cells.
Bone Marrow Transplants
The Immune System and the Nervous System
Bone marrow transplant is one possible remedy people with autoimmune disorders or people with cancer.
A close match is extremely important in bone marrow transplants because the body can reject the bone marrow cells and mature T cells from the bone marrow transplant can counterattack and destroy the recipient's tissues.
The immune system and the nervous system are linked
One connection is through the adrenal glands. As the adrenal glands release hormones due to stress messages from the brain, the hormones stifle the protective effects of antibodies and lymphocytes.
another link is that hormones and other chemicals convey messages among nerve cells also "speak" to cells of the immune system.