1. THE LYMPHATIC SYSTEM

2. The Lymphatic System  Two Semi-Independent Parts 1. Lymphatics (vessels) Collects leaked plasma & proteins from bloodstream (lymph) One way flow  toward heart Minivalves 2. Lymphoid tissues & organs Immune functions

3. Lymph Nodes  Contain macrophages to digest bacteria  Contain lymphocytes  B cells that generate plasma cells (antibody- releasing cells)  T cells that destroy tumor cells  More afferent than efferent vessels

4. Lymphoid Organs  Spleen – filters worn erythrocytes, bacteria, viruses, & other debris  Thymus – Releases hormone thymosin during childhood to help T lymphocytes mature  Tonsils – Trap foreign pathogens entering throat  Peyer’s patches – capture & destroy bacteria in the small intestine

5. The Immune System  Two Types of Resistance: 1. Nonspecific Resistance General protection against many pathogens Immediate Present since birth (inherited) 2. Specific Resistance Develops in response to contact with specific invaders

6. First Line of Defense: Barriers  Physical Barriers:  Skin  Hairs  Mucous Membranes Digestive Respiratory Urinary Reproductive  Cilia

7. First Line of Defense: Barriers  Chemical Barriers  Acid secretions – skin, vagina, stomach; kill bacteria  Sebum – oil of skin; toxic to bacteria  Lysozyme – enzymes in tears, saliva, and urine that destroys bacteria

8. Second Line of Defense: Cells  Nonspecific; Attack pathogens but don’t “remember” for next time.  Phagocytes – perform phagocytosis  Neutrophils – first to enter infected tissues; kill bacteria  Macrophages – slower; BIG eaters

9. Second Line of Defense: Cells  Natural Killer Cells (Killer T cells) –  Kills cancer cells  Kills virus-infected body cells  Lyses cell with perforin

10. Second Line of Defense: Inflammatory Response  Triggered when tissues are injured  Four Signs:  Redness  Heat  Swelling  Pain

11. Second Line of Defense: Inflammatory Response First Step: Alarm  Injured cells release histamine & kinins causing:  Vasodilation – increases blood flow  Leaky capillaries – causes edema  Activated pain receptors – forces rest  Chemotaxis – chemical gradient attracts phagocytes and other white blood cells

12. Second Line of Defense: Inflammatory Response  One hour later: Neutrophils perform diapedesis and start clean-up  8-12 hours later: Monocytes become macrophages!

13. Second Line of Defense: Inflammatory Response  Prevents the spread of infection  Disposes of cell debris & pathogens  Sets the stage for repair and healing

15. Second Line of Defense: Antimicrobial Chemicals  Interferon – protein released by virus-infected cells to prevent neighboring cells from reproducing new viruses  Urine

16. Second Line of Defense: Antimicrobial Chemicals  Complement System  At least twenty proteins always circulating  Activated by foreign antigens  Release chemicals: Vasodilators Chemotaxis Opsonization – cause foreign cell membranes to become sticky (and yummy)

17. Second Line of Defense: Fever  White blood cells secrete pyrogens  Triggers hypothalamus to raise body temperature  Inhibits bacterial growth  Stimulates phagocytosis  Causes liver & spleen to store iron, reducing availability for bacteria

19. Third Line of Defense: The Immune System  Two parts (working simultaneously):  Humoral Immunity – (antibody-mediated), antibodies present in the body fluids  Cellular Immunity – (cell-mediated), lymphocytes defend the body  Specific  Systemic  Has memory

20. Overview: Antigens  Nonself antigens  Self antigens – MHC (major histocompatibility) complex

21. Overview: Antibodies  AKA immunoglobulins (Igs)  Bind to specific antigen  Inactivates by:  Activating complement proteins = cell lysis  Binds to toxic secretions, rendering them harmless  Agglutination  Causes precipitation of soluble antigens

22. Effects of Antibodies

23. Cell Overview: Lymphocytes  Formed from hemocytoblasts in bone marrow  Mature by gaining immunocompetence (ability to respond to specific antigen)  In Bone marrow = B cells  In Thymus = T cells

24. Cell Overview: Macrophages  Antigen Presentation – present fragments of the antigens they’ve eaten on cell surface, for T cells to recognize  Secrete monokines, that further activate T cells

26. Primary Humoral Response  Antigen binds to immature B lymphocyte causing clonal selection  Helper T cells activate B cells  B cell makes clones!  Plasma cells (most) Make antibodies  Memory cells (few) Remember invader for faster response in future

27. Clonal Selection/T cell activation

28. B cell cloning/Antibody Production

29. Secondary Humoral Response  Achieved by memory B Cells in response to the old antigen  Faster  More prolonged  More effective

31. Active Immunity  Active immunity – activation of B Cells  Naturally – bacterial or viral infection  Artificially – vaccine Spared threat of the disease Still primes immune system for secondary response

32. Passive Immunity  Passive immunity – antibodies are transferred into the body\  Naturally – from mother to baby through placenta or breastmilk  Artificially – antivenin (snake bites), antitoxin (botulism, rabies, tetanus)  B cells are not challenged by antigen  Immunological memory does not occur

34. Cellular Immune Response: Helper T cells  Recruit other immune cells to join fight  Cannot recognize free-floating antigen  Macrophages present antigens: double recognition (self & non-self)

35. Cellular Immune Response: Helper T cells  Activation of Helper T cells:  Stimulates B cells & Killer T cells to grow/divide  Attracts other white blood cells to area  Enhances macrophage ability to eat & destroy  Releases lymphokines – chemicals that help destroy antigens

38. Cellular Immune Response: Other T cells  Suppressor T Cells – slows or stops the activity of B and T cells once the infection has been conquered  Memory T Cells – same as memory B cells  Killer T Cells (cytotoxic T cells)