the lymphatic system and immunity

1. The Lymphatic System and Immunity Chapter 14 Pgs 427-455

3. Introduction Pathogens: microorganisms responsible for human diseases Bacteria Viruses Fungi Parasites Lymphatic system Keeps us alive and healthy

4. Organization of Lymphatic System 3 components Lymphatic vessels Fluid (lymph) Lymphoid organs

5. Functions of Lymphatic System Production, maintenance, distribution of lymphocytes Respond to presence of: Invading pathogens Abnormal body cells (virus-infected cells, cancer cells) Foreign proteins (toxins released by bacteria) Return of fluid and solutes from peripheral tissues to blood Distribution of hormones, nutrients, and waste products from tissues of origin to general circulation

6. Lymphatic Vessels

8. Types of Lymphocytes T cells (Thymus dependent) 80% of circulating lymphocytes Cytotoxic T cells Directly attack foreign cells or body cells infected by viruses (cell-mediated immunity) Helper T cells Stimulate activities of both B and T cells Suppressor T cells Inhibit both T and B cells

9. Types of Lymphocytes B cells (Bone-marrow derived) 10-15% circulating lymphocytes Plasma cells Responsible for production and secretion of antibodies (immunoglobulins) Responsible for antibody-mediated immunity NK cells (Natural Killer) 5-10% Attack foreign cells, normal cells infected with viruses, and cancer cells Immunological surveillance

11. Lymphoid Nodules Masses of lymphoid tissue w/o a capsule Increase and decrease size depending on # lymphocytes present Found beneath epithelial lining of organs in: Respiratory system Digestive system Tonsils Peyer’s patches Urinary system

12. Lymphoid Organs: Lymph Nodes

13. Lymphoid Organs: Thymus

14. Lymphoid Organs: Spleen

15. The Lymphatic System and Body Defenses Nonspecific Defenses Do not distinguish one threat from another Physical barriers Phagocytic cells Immunological surveillance Interferons Complement Inflammation Fever Specific Defenses Protect against particular threats Develop after birth Dependent on activity of lymphocytes B cells T cells

18. The Complement System

20. Macrophage

21. Specific Defense: The Immune Response Respond to specific antigens T cells Cell-mediated immunity (cellular immunity) Provide defense against abnormal cells and pathogens in living cells B cells Antibody-mediated immunity (humoral immunity) Provide a defense against antigens and pathogens in body fluids

22. Immune System

23. Forms of Immunity Either innate or acquired Innate Genetically determined Acquired Active or Passive Active Immunity Naturally acquired immunity Induced active immunity Passive Immunity Induced passive immunity Natural passive immunity

25. Properties of Immunity Specificity Versatility Memory Tolerance

26. Overview of Immune Response

28. T Cells and Cell-Mediated Immunity T cells recognize antigens when bound to membranes of other cells Membrane receptors called major histocompatibility complex (MHC) proteins 2 classes Class I MHC proteins Class II MHC proteins

29. Class I MHC Proteins Found on the surfaces of all of our cells MHC proteins bind small peptide molecules normally present on cell membrane Normal peptides: T cell ignores Abnormal, virus, or bacteria (nonself): T cell activated Destroys abnormal/infected cell

30. Class II MHC Proteins Found only on membranes of lymphocytes and phagocytic antigen-presenting cells (APCs) Such as monocyte-macrophage group, free and fixed macrophages Specialized for activating T cells against foreign cells and proteins Phagocytic APCs engulf and break down foreign antigens or pathogens Fragments of foreign antigens displayed on phagocytic cell’s membrane Bind to Class II MHC proteins T cells come in contact and become activated, starting the immune response

32. T Cells T cell activation for both occur when MHC protein contains specific antigen T cell programmed to detect Once activated, T cells divide and differentiate in to cells with specific function in immune response Cytotoxic T cells Helper T cells Memory T cells Suppressor T cells

33. Cytotoxic T Cells Responsible for cell-mediated immunity Activated by exposure to antigens bound to Class I MHC proteins Activated cells under cell division that produce active cytotoxic T cells and memory cells Track down and attack bacteria, fungi, protozoa, or foreign transplanted tissue

34. Cytotoxic T Cells Destruction occurs by: Releasing perforin (destructive protein) Ruptures antigenic cell membrane Secreting lymphotoxin (poison) Kills target cell Apoptosis Genetically programmed cell death T cells activate the genes within the target cell Also called Killer T cells

37. Apoptosis and Macrophages

38. Helper T Cells Activated by exposure to antigens bound to Class II MHC proteins Activated ? divide to produce Active Helper T cells and memory cells Release variety of cytokines that: Coordinate specific and nonspecific defenses Stimulate cell mediated and antibody-mediated immunity

39. Memory T Cells During cell division for both cytotoxic and helper T cells, some develop into memory cells Remain in reserve If same antigen attacks 2nd time, memory T cells immediately differentiate into cytotoxic T cells and helper T cells Allows for more rapid and effective immune response

40. Suppressor T Cells When activated, depress responses of other T and B cells Does not occur immediately Takes much longer for these cells to become activated Act after initial immune response

41. B Cells and Antibody-Mediated Immunity: B Cell Activation Each B cell carries its antibody molecules in its cell membrane If ISF contains antigens that can bind to antibodies, B cells become sensitized Antigens enter B cell and become displayed on Class II MHC proteins on surface of B cell Helper T cell activated by same antigen attaches to MHC protein-antigen complex and secretes cytokines that: Promote B cell activation Stimulate B cell division Accelerate plasma cell production Enhance antibody production

42. B Cell Activation Activated B cells divide several times Produce daughter cells that differentiate into: Plasma cells Synthesize and secrete large numbers of antibodies on surface of sensitized B cells Memory cells Similar to memory T cells If exposed to same antigen, will differentiate into plasma cells

46. Antibody Structure Consist of short and heavy chains of polypeptides Each chain has constant and variable segments Constant heavy chains form base of antibody molecule B cells produce only 5 types of constant segments Specificity depends on variable segments of light and heavy chains Free tips contain antigen binding sites (very specific for each type of antigen) Antigen-antibody complex Forms when antibody binds to proper antigen Binds to sites and leads to B cell sensitization and an immune response

49. Classes of Antibodies (Immunoglobins Igs) IgG Largest and most diverse Resist many viruses, bacteria, bacterial toxins Can cross placenta What type of immunity is that? IgM Circulate; attack bacteria IgA Found in exocrine secretions Ex? Attack pathogens before they enter the body IgE When bound to antigen, stimulates basophils and mast cells to release chemicals to stimulate inflammation IgD Attached to B cell and involved in their activation

50. Antibody Function Neutralization Agglutination and Precipitation Activation of a complement Attraction of phagocytes Enhancement of phagocytosis Stimulation of inflammation

51. Primary and Secondary Responses to Antigen Exposure

52. Cool Links! Fun immune game http://nobelprize.org/medicine/educational/immunity/index.html Cool Cytotoxic T cells http://www.cellsalive.com/ctl.htm Copy and paste them into your browser