The Immune System

By Lexy Mcalpin

All Systems Go:• The immune system is the body's defense

against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade body systems and cause disease.

• The immune system is made up of a network of cells, tissues, and organs that work together to protect the body. The cells involved are white blood cells, or leukocytes, which come in two basic types that combine to seek out and destroy disease-causing organisms or substances.

• The organs of the immune system are positioned throughout the body. They are called lymphoid organs because they are home to lymphocytes, small white blood cells that are the key players in the immune system.

• Bone marrow, the soft tissue in the hollow center of bones, is the ultimate source of all blood cells, including lymphocytes. The thymus is a lymphoid organ that lies behind the breastbone.

• Lymphocytes known as T lymphocytes or T cells (“T” stands for “thymus”) mature in the thymus and then migrate to other tissues. B lymphocytes, also known as B cells, become activated and mature into plasma cells, which make and release antibodies.

• Lymph nodes, which are located in many parts of the body, are lymphoid tissues that contain numerous specialized structures.

• T cells from the thymus concentrate in the paracortex.• B cells develop in and around the germinal centers.• Plasma cells occur in the medulla.

•Bone MarrowAll the specialized cells of the immune system are formed

in the bone marrow, where they mature. When they are fully mature they move into the blood stream where they do their work.

•ThymusThis small but important organ is where lymphocyte

precursors become thymocytes, which in turn mature into T-cells. In addition, the thymus actually chooses which T-cells are best suited for the immune system. The remaining ones are eliminated by the body, assuring a healthy, effective immunity.

•SpleenYou can think of the spleen as a filter for the blood. It catches foreign

material in the blood and activates different types of immune system cells.

•Lymph NodesThe lymph nodes filter foreign material from the lymph fluid. Fluid

that drains from various tissues in the body collects in the lymph system and passes through the nodes, being filtered as it passes.

T-Cells:There are two subsets of T-cells: CD4 cells and CD8 cells. CD4 cells

secrete factors that activate other white blood cells that participate in the immune response. HIV attacks CD4 cells, damaging the body's ability to initiate the immune response. CD8 cells are important in directly killing tumor cells, viral infected cells and some parasites.

WHAT functions

with the

IMMUNESYSTEM.

• Skeletal System: The skeletal system makes up the framework of the body and allows movement for when our muscles contract. This system protects internal organs and produces blood cells. It also stores minerals such as calcium and releases them into the body when they are needed.

• The skeletal system provides the blood cells that the immune system needs as a method of transportation

• Integumentary System: The integumentary system contains receptors that respond to touch, regulates body temperature, and protects the inside of the body from damage.

• The integumentary system works along with the immune system in defending your body against various diseases, for this system fights infection on the outside of the body.

• Circulatory System: The circulatory system is responsible for transporting materials, such as nutrients, water, and oxygen, throughout the entire body. It transports those materials to billions of body cells and carries away wastes such as the carbon dioxide that body cells produce.

• The immune system works closely with the circulatory system for transportation needs by means of blood cells, allowing the immune cells to travel throughout the body and survey the body for infection.

WHAT KIND?• What is natural and acquired immunity?

1. Natural immunity is created by the body's natural barriers, such as the skin, and protective substances in the mouth, the urinary tract, and on the eye surface. Another type of natural immunity is in the form of antibodies passed on from mother to child.

2. Acquired immunity develops through exposure to specific foreign particles which are "remembered" by the body's immune system. When that antigen enters the body again, the immune system "remembers" exactly how to respond to it.

Active and Passive ImmunityActive immunity

Lymphocytes are activated by antigens on the surface of pathogensNatural active immunity - acquired due to infectionArtificial active immunity – vaccination

Takes time for enough B and T cells to be produced to mount an effective response.

Active and Passive ImmunityPassive immunityB and T cells are not activated and plasma

cells have not produced antibodies.The antigen doesn’t have to be encountered

for the body to make the antibodies.Antibodies appear immediately in blood but

protection is only temporary.

Active and Passive ImmunityArtificial passive immunity

Used when a very rapid immune response is needed e.g. after infection with tetanus.Human antibodies are injected. In the case of tetanus these are antitoxin antibodies.Antibodies come from blood donors who have recently had the tetanus vaccination.Only provides short term protection as abs destroyed by phagocytes in spleen and liver.

Active and Passive ImmunityNatural passive immunityA mother’s antibodies pass across the

placenta to the foetus and remain for several months.

Colostrum (the first breast milk) contains lots of IgA which remain on surface of the baby’s gut wall and pass into blood

Homeostasis:

• The lymphatic system, also known as the immune system, is responsible for protecting the body from foreign invasion. Lymph, lymph nodes, vessels, tonsils, thymus and the spleen all comprise the organs of the lymphatic system to help keep temperature maintained, and bodily fluids free from foreign particles maintaining homeostasis.

FUN FACT!Lack of immune system response

indicates immunodeficiency!This may be acquired through

family genetics or may be acquired through

infection(Mrs. Sullivan)

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