1. Brian Stith, Karina Barragan, Salwa Hanna
The Body's Defenses
Brian Stith, Karina  Barragan, Salwa Hanna

2. Body Defenses All environments include millions of microbes
Microbes- tiny organisms to tiny to see in a microscope that are abundant on earth.
Bodies have three different layers of defenses that protect us from these invisible and potentially harmful substances.
First Layer and second layer are classified Nonspecific Defense third layer is Specific Defense.

3. External Barriers
The first line of our body's protective barrier is called our External Barrier.
Prevent infects
Includes:
Skin
Mucous Membrane
Secretion of skin and mucous membrane

4. Internal Barriers The second layer of our bodies defenses. Includes:
White blood cells (phagocytes & NK cells)
Defensive Proteins (Interferons & Complement proteins)
The inflammatory response(Histamine, Prostaglandins, and Pyrogens)

6. Inflammatory Response

7. The Lymphatic System
Network of vessels, numerous lymph nodes, bone marrow and other organs.
Lymph Nodes- Saclike organs packed with macrophages and a white blood cell called lymphocytes
Two functions- Return tissue fluid and fight infections

8. Lymphatic Collecting Vessels and Regional Lymph Nodes `

9. Specific Defenses: The Immune System
The immune system consists of a large collection of cells that work together to present a specific response to an infection.
Presents elaborately coordinated response to infection.
Response must first be primed.
Antigen is a foreign substance that elicits an immune response.
Most are molecules on the surface of viruses or other surfaces of other foreign cells.

10. When the immune system detects an antigen, it produces defensive proteins called antibodies which are proteins found in blood plasma that attaches to one particular kind of antigen and helps counter its effects. The immune system has a remarkable "memory" Can "remember" antigens it encountered before and react against them more promptly and vigorously on second or subsequent exposure. Immunity is usually acquired by a natural infection or achieved by a vaccination. A vaccine is composed of harmless variant of a disease- causing microbe or one of its components. Once a person is successfully vaccinated, the immune system will respond quickly, if exposed to the microbe.

11. Active immunity involves the production of antibodies by the body conferred by recovering from an infectious disease. Passive immunity is obtained by acquiring ready-made antibodies or immune cells and is temporary lasting for only a few weeks of months.

13. Lymphocytes, a type of white blood cells, produce the immune response.
Originate from stem cells in bone marrow
Immature lymphocytes continues to develop in bone marrow and becomes B cells
Other immature lymphocytes migrate via blood into a gland in the chest, Thymus, and becomes T cells
Humoral immune response is the first type of immunity in which B cells secrete antibodies as a form of defense.
Defends mostly against bacteria and viruses present in body fluids.
Second type of the immune response, cell-mediated immune system in which T cells circulate in the blood and lymph attacking infected body cells.
T cells also work against fungi and protozoans.
T cells are important in protecting the body from its own cells if they become cancerous.
T cells function indirectly.

14. When a T cell or B cell develops in either the thymus or bone marrow, cell synthesizes molecule of a specific protein and build them into its plasma membranes.
Protein molecules are antigens receptors that stick out from the cell's surface.
All antigens receptors are capable of binding to only one specific type of antigen.
Once surface proteins are in place, a B cell or T cells can recognize a specific antigen and mount immune response against it. Tiny fraction of the immune system's lymphocytes will ever be used but all are available if needed.

15. Antibodies produced by B cells serve as molecular weapons of defense.
Typical antibodies consists of two longer  polypeptide chains  and two shorter chains.
Chains join to form a Y shape.
In humoral immune response, an antibody binds and recognizes a certain antigen and by doing this, it helps counter its effects.
Structure of antibody allows it to perform these functions

17. Main role of antibodies in eliminating invading microbes and molecules is to mark the invaders Antibody marks an antigen by combining with it to form antigen-antibody complex.
Binding triggers one of several mechanisms that help destroy the invader.
Binding sometimes blocks antigens making it harmless.
Sometimes can cause viruses, bacteria, or foreign eukaryotic cells to form large clumps that are easily captured by circulating phagocytes.
May activate complement proteins that destroy marked antigens.

18. Responding to the Invaders
Immune system stops infections by destroying antigens-bearing invaders.
Detects antigen, responds by increasing number of cells that either produce defensive proteins of attack infected cells.
Clonal Selection is the production of a lineage of genetically identical cells.
Mechanism that underlies the immune system's specificity and memory or antigens.

20. Effector cells are specialized for defending against the very antigen that triggered the response. Antibody molecules produced by a single clone of cells are known as monoclonal antibodies.
Scientists can artificially produce monoclonal antibodies in large quantities that have practical uses including home pregnancy tests.
The primary immune response is the first exposure of lymphocytes to an antigen that takes several days to produce effector cells via clonal selection.
Antibodies produced reach peak level about two weeks after the first exposure and then start to decrease
Effector cells lives only 4  or 5 days

21. Colonial selection also produce memory cells that can live for decades in the lymph nodes are ready to be activated by a second exposure to the antigen. Secondary immune response is when the antigen is encountered again and the memory cells bind to it faster.
Memory cells multiply quickly.
New clone produces antibodies that are more effective.
Two main types of T cells are helper T cells and cytotoxic T cells. Helper T cells help active other types of T cells and may help B cells produce antibodies.

24. Cytotoxic T cells are the only T cells that actually kill other body cells.
Identify infected body cell same way helper T cells identify target through binding of a membrane receptor to a self-nonself complex.

25. Immune Disorders
Allergies: Are abnormal sensitivity to antigens in the environment. Allergens: Antigens that cause allergies. Ex. Protein molecules on pollen grains, feces of tiny mites in house dust, animal dander.

26. Two-Stage Allergic Reaction Sequence
Stage 1: Sensitization
1. When the allergens enters the bloodstream it binds to B cells with complementary receptors.
2. B cells proliferate through the clonal section and let out large amounts of antibodies of that allergen.
3. Some of the antibodies attach to the receptor proteins of the mast cells, may cause chemicals that trigger inflammatory response in a normal human body.

27. Two-Stage Allergenic Reaction Sequence Cont.
Stage 2: Allergy symptoms begin
When the same allergens re-enters the body and binds to the antibodies of the mast cells.
The mast cells release histamine causing allergy symptoms.
Ex. Sneezing, coughing, itching.

29. The most dangerous type of allergic reaction
Anaphylactic shock: a sudden release of inflammatory chemical making blood vessels to dilate abruptly causing fatal drop in blood pressure.

30. Autoimmune Diseases
Everyone has their particular collection of proteins that provide the molecular "fingerprints". The immune system can distinguish the individual's cells from another. Ex. Organ transplant
To minimize rejection doctors look for donors with very similar self proteins.

31. Autoimmune Diseases Cont.
Autoimmune diseases: results when the immune system turns against the individuals own molecules. Ex. Lupus B cells make antibodies against many molecules, even histones and DNA.

32. Immunodeficiency Diseases
Immunodeficiency Disease: lack of one or more components of the immune system. Ex. Severe combined immunodeficiency (SCID) A marked defect in both T cells and B cells.

33. AIDS
Has killed more than 25 million people worldwide since million are currently living with the new AIDS virus HIV. HIV destroys the immune system and often attacks help T cells, usually resulting in death.