KEY CONCEPT The immune systems consists of organs, cells, and molecules that fight infections.

1. KEY CONCEPTThe immune systems consists of organs, cells, and molecules that fight infections.

2. Immunology- Three lines of defense Barriers, Nonspecific responses, specific-targeted response

3. First line of defense-Barriers • Physical and chemical barriers- • Nonspecific-doesn’t distinguish, same for all invaders • Skin-outer layer of tough,dead cells • Mechanical barrier • Constantly shedding • Bacteria can’t enter. • Sweat and oil glands- chemical barrier • secrete acids • Sweat has lysozyme- breaks down cell walls.

4. Barriers continued • Mucous membranes • Mechanical barrier • Mucous traps pathogens • Cilia moves trapped particles out of body • Secretions- • Saliva and tears- • washing action • Lysozyme enzymes breaks down cell walls. • Stomach acids, enzymes • Destroy pathogens • Microorganisms in foods,drinks

5. Second line of defense- • Nonspecific- doesn’t single out a specific pathogen. • When pathogens get through primary first line of defense. • Includes- • Pathogen destroying white blood cells • Inflammatory response • Specialized proteins

6. White Blood Cells-wbcs • bloodstream, interstitial fluid, and lymphatic system • attacking invaders • Macrophages ( big eaters) mainly in interstitial fluid. • macrophage engulfs the organism. • the pathogen is drawn into the macrophage, where enzymes such as lysozyme kill the pathogen.

7. Neutrophiles-smaller and more numerous • 60-70% of wbcs. • Multilobed- PMNs • Neutrophils also kill by phagocytosis • neutrophil releases chemicals - kill the invading pathogen. Chemicals also kill the neutrophil. • White blood cells can identify certain proteins and carbohydrates on the surface of an invading pathogen. These "foreign" molecules triggers the cells' responses. • Pus- fluid containing wbcs and debri from dead tissue

8. Natural killer cell (NK) • Do not kill pathogens directly • Recognize body cells that have become infected by a virus • Release chemicals to break infected cell’s membrane • Also attack cancer cells/ abnormal cells before a tumor is formed.

9. Inflammatory Response • Nonspecific defense characterized by 6 characteristics • redness, heat, swelling, pain, fever phagocytosis. • mast cells release histamine • nearby blood vessels to dilate (expand). • Increases the volume of blood flowing to the injured tissue. • Other chemicals attract additional phagocytes and other white blood cells to the area, where they pass through the leaky blood vessel walls into the interstitial fluid • Local increase of blood flow, fluid, and white blood cells produces the redness, heat, swelling, and pain at the injured area.

10. Low fevers stimulate white blood cells to mature. • In fever, body temperature increases. • High fevers can cause seizure, brain damage, and even death.

12. Specialized Proteins • Interferon- • a family of proteins produced by T-cells or virus-infected cells. • The infected cell may die, but its interferon reaches healthy cells in the area, stimulating them to produce proteins that interfere with virus reproduction. • Interferon is effective against many viruses and is therefore nonspecific. Interferon seems to be effective against viruses that cause the flu and the common cold. • Genetically engineered

14. Third line of defense • Immune system • Specific • Recognizes specific pathogens, cancer cells,certain chemicals • Immune system must recognize self from nonself.

15. antigens virus Cells of the immune system produce specific responses. • Specific immune responses begin with the detection of antigens. • Antigens are surface proteins on pathogens. • Means antibody generating. • Each pathogen has a different antigen.

16. B cell pathogen antibodies T cell memory B cells activated B cells • 1. Humoral immunity - B cells to produce antibodies. There are two specific immune responses.

17. pathogen antigens antigens T cell receptors activated T cells memory T cells 2.Cellular immunity -T cells -destroys infected body cells.

18. B cell T cell Both responses produce memory cells. • specialized T and B cells • provide acquired (active) immunity

19. Immunity • Resistance to a pathogen that causes disease. • Antigens- large molecules of protein or polysaccharides that induce a specific response. • Rarely can be lipids or nucleic acids • Small molecules are poor antigens- • They are not attracted to macrophages.

20. Examples of antigens • Bacterial capsules • Lipopolysaccharides of gram neg. bacteria • Glycoproteins in cell membranes • Attachment sites on viruses that interact with mammalian cells. • Soluble bacterial toxins,venoms • Pollens, food, house dust

21. Properties of antigens- • Foreign to host • Capable of inducing an antibody response • Large • Antibody must bind to the antigen • Epitope- Specific location on antigen that combines with antibody • Hapten- if molecule is too small to induce an antibody response by itself it combines with a carrier molecule (protein). Ex. penicillin

24. Antibodies • Antibodies- proteins found on the surface of certain white blood cells, or in blood plasma, that attach to particular antigens. • Also known as immunoglobulins- Ig

25. Specific B-Cell Receptor: Immunoglobulin • Composed of 4 polypeptide chains: • 2 identical heavy chains (H) • 2 identical light chains (L) • Y shaped arrangement – • ends of the forks formed by light and heavy chains contain a wide range of variable antigen binding sites • Variable regions • Constant regions

28. T-Cell Receptors for Antigen • Formed by genetic recombination, with variable and constant regions • 2 parallel polypeptide chains • small, without humoral functions

30. Classes of Immunoglobulins 5 classes of Immunoglobulins (Ig): 1. IgG - long term immunity- crosses placenta 2. IgA – secretory antibody- mucous 3. IgM – immediate response 4. IgD – receptor on B cells 5. IgE – allergic response

32. Classes of Antibodies(Ab) • IgG- • 2 antigen binding sites • Crosses placenta • 80% of all immunoglobulins • IgM- • 5 or more binding sites • Largest • Found in plasma • 1stAb after injection of antigen • Especially effective against gram negative bacteria

33. Immunity Titers

34. IgA- • Secretions of exocrine glands- mother’s milk • Saliva, tears • Effective against bacteria and viruses • IgD- • 2 sites • On B cells that recognizes antigens • Function difficult to determine • IgE- • Least amount • In allergic reactions • Allergen- IgE- mast cells- histamine.

35. Lymphocytes- special wbcs that recognize specific invaders. In bone marrow, lymphocytic stem cells differentiate into either T or B lymphocytic cells. B cells mature in the bone marrow B- bursa of birds T cells migrate to thymus gland to mature. Mature T and B cells migrate to lymph nodes and other parts of the lymphatic system. Lymphocytes

37. B Cells and Humoral Immunity Antibody proteins on the surface of B cells act as specific receptors for antigens. • ~ 100 million different B cell surfaces • B Cells act primarily against bacteria and viruses in body fluids outside of cells.

38. Humoral Immunity

39. Steps: Activation occurs: B cell with matching antigen receptor binds to the antigens of the pathogen. B cell grows and clones itself, forming millions of identical cells. Each cell can become a plasma cell, which produces and secretes antibodies specific to the original antigen that activated the original B cell. Plasma cells are carried by lymph and blood to sites of infection in the body. Termed humoral immunity since antibodies travel in the blood and other body fluids once called “humors”.

40. T cells and Cell-Mediated Immunity • T cells directly attack infected host cells that contain bacteria or viruses. • Each T cell has a receptor for a specific antigen.

41. Steps: 1. The infecting pathogen’s antigens are displayed on the host body cell. 2. Activation occurs- the antigens on the host body cell bind to receptors on the matching T cell, activating the T cell. • 3. Activated T cell divides producing clones. • 4. T cell clones become cytotoxic T cells- • 5. Cytotoxic T cells attack infected cells. • bind to infected cell membranes • secrete perforin - pokes holes in the membrane-leakage and cell death.

43. Role of Helper T Cells • Role in both humoral and cellular immunity. • Helper T cells are activated by binding to macrophages that display antigens of a pathogen. • Helper T cells then secrete chemicals that activate both cytotoxic T cells and B cells

44. How the Immune System Remembers Pathogens • Memory B and T cells- • After the first exposure of a pathogen some of the B and T cells remain in your body. • The first formation of T and B cells is called the primary immune response. • A slower and weaker response- requires time • Second exposure to the same pathogen- Secondary immune response. Quicker and stronger response- don’t develop symptoms Memory T cells produce cytotoxic T cells Memory B cells produce plasma cells that secrete Ab

46. Passive and Active Immunity • Passive immunity- receive antibodies from another source • Antibodies to fetus from mother. • Travelers receive antibodies rather than antigens. • hepatitis A • Lasts a short time- weeks or months • Active Immunity- your body produces antibodies • Get disease. • Vaccines- • Heat killed dose of pathogen (antigen) • Attenuated (very low, nonvirulent) dose of pathogen • Booster shot- tetanus- additional dose of antigen- needed because initial memory cells have died