NOTES: CH 43, part 1 The Immune System - Nonspecific & Specific Defenses ( )

Transcription

1 NOTES: CH 43, part 1 The Immune System - Nonspecific & Specific Defenses ( )

2 The lymphatic system is closely associated with the cardiovascular system.

3 LYMPHATIC PATHWAYS Lymphatic capillaries microscopic, closed-end tubes that extend into intercellular spaces receive LYMPH through their thin walls (LYMPH = the fluid of the lymphatic system) lymphatic capillary networks parallel blood capillary networks

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6 Functions of lymph: 1) returns to the bloodstream small proteins that leaked out of blood capillaries 2) transports foreign particles, such as bacteria or viruses, to lymph nodes

7 **if lymph movement is impaired, it may accumulate within the intercellular spaces and produce EDEMA, or swelling (example: after surgery, the lymphatic vessels and lymph nodes around the wound may be damaged, causing fluid to accumulate around the surgery site and lead to swelling)

8 Lymph Nodes: Structure of a Lymph Node: lymph nodes are subdivided into nodules nodules contain masses of lymphocytes and macrophages

9 Locations of Lymph Nodes: lymph nodes aggregate in groups or chains along the paths of larger lymphatic vessels

10 Functions of Lymph Nodes: filter potentially harmful foreign particles from lymph are centers for the production of lymphocytes (attack invading viruses, bacteria, parasites, etc.) contain phagocytic cells (engulf and destroy foreign substances, damaged cells, cellular debris)

11 Thymus: THYMUS AND SPLEEN shrinks slowly after puberty contains large numbers of LYMPHOCYTES which mature into T CELLS (T lymphocytes) important in providing immunity (more on these later )

12 Spleen: largest lymphatic organ resembles a large lymph node (divided into lobules)

13 Spleen: spaces within splenic lobules are filled with blood contains many macrophages, which destroy/remove foreign particles and damaged RBCs from the blood **the spleen filters blood as the lymph nodes filter lymph!**

14 So, how does the body defend itself???

15 The body has nonspecific and specific defenses against infection / pathogens. Why don t YOU have mold on your skin???

16 PATHOGEN: a disease-causing agent; causes infection -pathogens include: viruses bacteria fungi protozoans

17 Nonspecific Defenses: general defense provide protection against many different pathogens involve physical and chemical barriers, fever, inflammation, phagocytosis

18 very precise Specific Defenses: target certain pathogens also known as IMMUNITY involve specialized lymphocytes (T cells and B cells) that recognize and respond to specific pathogens **nonspecific defenses are quick to respond; specific defenses are slower-torespond

19 NONSPECIFIC DEFENSES 1) Species Resistance each species is resistant to certain diseases that may affect other species examples: measles, mumps, gonorrhea, and syphilis infect humans but not other animal species one species may be resistant to a disease that affects another species because its tissues somehow fail to provide a suitable environment for the pathogen (temperature, chemical environment, receptors, etc.)

20 2) Mechanical Barriers = FIRST LINE OF DEFENSE mechanical barriers / physical barriers include: -skin (and associated hairs) -mucous membranes -fluid (sweat and mucus) as long as they remain intact, they can keep out many pathogens

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22 SKIN MUCUS SALIVA

23 **all other nonspecific defenses are considered the SECOND LINE OF DEFENSE

24 3) Chemical Barriers gastric juice: contains hydrochloric acid and enzymes (e.g. pepsin) that are lethal to pathogens tears: contain the enzyme LYSOZYME (which has antibacterial action) the salt in perspiration accumulates on the skin and kills bacteria on the skin

25 3) Chemical Barriers (cont.) INTERFERONS: chemicals released by virus-infected cells; they stimulate other immune cells to: -synthesize antiviral proteins that stimulate phagocytosis, block virus replication

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27 Interferons: most effective against cold and flu virus now mass-produced by recombinant DNA technology to be potentially used as treatment for viral infections and cancer!

28 3) Chemical Barriers (cont.) COMPLEMENT SYSTEM: group of 30 proteins; catalyze a series of steps resulting in lysis of invading microbes and/or inflammatory response

29 4) Fever higher body temperature increases the rate of phagocytic cells also lowers iron levels in the blood (bacteria and fungi require iron, so this slows their growth)

30 5) Inflammation produces: localized redness, swelling, heat and pain HISTAMINE and prostaglandins released by damaged tissues attract WBCs to the site the mass of WBCs, bacterial cells, and damaged tissue forms a thick fluid called PUS

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33 6) Phagocytosis removes foreign particles from the lymph and blood the most active phagocytes in blood are NEUTROPHILS and MONOCYTES Monocytes give rise to MACROPHAGES

34 MACROPHAGES are found in the linings of blood vessels in the: -bone marrow -liver -spleen -lungs -lymph nodes

35 EOSINOPHILS: kill antibody-coated parasites

36 Specific Defenses / Immunity

37 Immune System the body s third line of defense characterized by: specificity diversity self / non-self recognition memory

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39 ANTIGENS ANTIGENS: specific foreign molecules that trigger an immune response; usually located on a cell s surface -antigens include: proteins polysaccharides glycoproteins glycolipids

40 ANTIGENS before birth, body cells sort self proteins and other large molecules lymphocytes develop receptors that allow them to differentiate between nonself (foreign) and self antigens nonself antigens combine with T cell and B cell surface receptors and stimulate these cells to cause an immune reaction

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42 LYMPHOCYTES (T and B Cells) originate in the red bone marrow some reach the THYMUS, where they mature into T CELLS others, the B CELLS, mature in the RED BONE MARROW both T cells and B cells reside in lymphatic tissues and organs (lymph nodes, spleen, etc.)

43 LYMPHOCYTE FUNCTIONS **a lymphocyte must be ACTIVATED before it can respond to an antigen**

44 Antigen Presentation: Carried out by a group of approx. 20 glycoproteins that make up the MAJOR HISTOCOMPATIBILITY COMPLEX (MHC)

45 Two main classes of MHC molecules: Class I MHC: located on all nucleated body cells *cytotoxic T cells (T C ) bind to fragments of antigens displayed by class I MHC Class II MHC: found only on specialized cells (macrophages, B cells, activated T cells) *helper T cells (T H ) bind to fragments of antigens displayed by class II MHC

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48 Antigen-Presenting Cells (APCs): -cells that take up antigens (B cells, macrophages); -engulfed foreign matter binds to a class II MHC molecule and is conveyed to the outside of the APC; -foreign antigen is recognized by a helper T cells (T H ); -this interaction is enhanced by CD4, a membrane protein on T H cells.

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50 *CLONAL SELECTION: antigen-specific selection of a lymphocyte; activates lymphocytes to divide and differentiate to produce CLONES of effector cells & memory cells designed to eliminate the antigen that provoked the initial response SPECIFICITY & MEMORY!

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53 PRIMARY IMMUNE RESPONSE PRIMARY IMMUNE RESPONSE: the first reaction / response to an antigen (first exposure) during this response, antibodies are produced for several weeks antibodies first show up within 5-10 days some B cells remain dormant as MEMORY B CELLS

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56 SECONDARY IMMUNE RESPONSE SECONDARY IMMUNE RESPONSE: the second response (exposure) to an antigen rapid response due to memory cells produced during the first exposure antibodies produced within a day or two

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