Lymphatic Immune System

1. Lymphatic Immune System Chapter 14

2. Introduction Intro to Immunity • Includes: • Network of vessels that transports fluids • Similar to cardiovascular • Organs, etc: • Lymph nodes/vessels/fluid, capillaries, veins/arteries, thymus, spleen, bone marrow • Functions: • Drain interstitial fluid back to the circulatory system • Dietary lipid absorption/transport • Initiate & regulate immune responses

4. Flow of Lymph • Lymphatic capillaries → Lymphatic vessels → Lymphatic Trunks → Collecting Ducts → Veins • The lymph will also pass through lymph nodes found along vessels

5. Lymphatic Capillaries • Closed-ended tubes • Form network with blood capillaries • Thin-walled • Fluid inside is called lymph

6. Lymphatic Vessels and Trunks • Lymphatic vessels • Structure is very similar to veins • Lymphatic Trunks • Larger vessels than lymphatic vessels; drain into collecting ducts

7. Collecting Ducts • Two Main Ducts • 1) Thoracic Duct- collects lymph drained from the lower limbs, abdomen, left upper limb, and left side of the thorax, head, and neck • 2) Right Lymphatic Duct- collects lymph drained from right upper limb and right side of the thorax, neck, and head

9. Tissue Fluid • Interstitial fluid surrounding capillaries • Constant movement in and out of capillaries • Generally same composition as plasma (except doesn’t contain plasma proteins) • Some excess fluid stays in tissue and is not recollected by capillaries

10. Formation of Lymph • Volume pressure of interstitial fluid causes some of the fluid to enter lymphatic capillaries • Lymph will return to the bloodstream but will be filtered along the way • Removing: Wastes, pathogens, carbon dioxide

11. Movement of Lymph • Controlled by: • Skeletal muscle movement • Pressure changes (due to breathing) • Valves keep the movement going in one direction

12. Lymph Node Function • Filter foreign particles from blood before returning the lymph to the blood stream • Immune surveillance

13. Lymph Nodes (outside structure) • Usually small and bean shaped • Afferent lymphatic vessels: • Carry lymph into lymph node • Come in at various points along convex surface • Efferent Lymphatic vessels: • Carry lymph out of lymph node • Come out at hilum (area on the concave side) • Blood vessels and nerves enter at hilum

15. Lymph Node (Inside structure) • Connective tissue encloses lymph node and creates sub-compartments inside • Compartments are lymph nodules • Lymph sinus: space inside the nodule • Sinuses are filled with lymphocytes and macrophages

17. Thymus • Bilobed structure found in the chest region • Largest during childhood • Creates T-cells • Also an endocrine gland • Releases thymosins (make T-cells mature after leaving the thymus)

18. Spleen • Largest lymphatic organ • Found near stomach • Similar structure to lymph nodes • Sinuses contain blood instead of lymph • White pulp • High in lymphocytes • Red pulp • High in red blood cells, lymphocytes, and macrophages • Filters Blood

19. Immunity • Protection against pathogens • Pathogens include: • Viruses • Bacteria • Fungi • Protozoans

20. Types of Immunity • Innate vs Adaptive • Natural vs Artificial • Active vs Passive

21. Innate Defenses • Species specific • First line of defense: • Skin and mucous layers • Second line of defense: • Chemical barriers • Tears, gastric juices, and sweat • Interferons • Fever • Inflammation • Phagocytosis

22. Adaptive Immunity • Third line of defense • Lymphocytes are responsible • Lymphocytes: WBCs specific for adaptive immunity • Types of lymphocytes: B and T cells • Responds to specific antigen on the invading pathogen

23. Origin of Lymphocytes • Undifferentiated lymphocytes made by fetal bone marrow • T cells • Lymphocytes travel to thymus and become T cells • T cells either circulate in blood or are found in lymph system • B cells • Made in marrow • B cells either circulate in blood or found in the lymph system

24. Differences in response • 1) Cellular Immune response • Attack up close • Performed by T cells • 2) Humoral immune response • Attack from afar • Performed by B cells

26. Helper T cells • Antigen-presenting cells processes and displays antigen of pathogen • Displayed antigen must be matched with a circulating helper T cells antibody receptor • Helper T cell is activated

28. Cytotoxic T cells • Known as Tc • Function: • Attack cells infected virus or cancerous cells • Release destructive enzymes into pathogen • Must be activated by a matching antigen

29. B cells • Sequence of events: • B cell must match with an antigen • Activated Helper T cell secrete cytokines • Cytokines make B cell proliferate to form plasma cells and memory cells • Plasma cell secrete antibodies

30. Antibodies • Globular proteins; all immunoglobulins • Contain heavy and light protein chains • Contain variable region (area that is specific to antigen – foreign body- attachment)

31. Antibody Types

32. Antibody Function • Two types: • 1) Attack directly • Allows antibody to more easily phagocytize cells, eliminate them • Types of Direct Attack: • Agglutinate (Clump pathogens together) • Precipitate (Make pathogen insoluble) • Neutralize (Cover or destroy toxic part of antigen)

33. Antibody Function • 2) Complement • Bind antigens • Starts a series of rxns that activate the complements circulating in the plasma • Complement Function: • Opsonization- coating antigen-antibody complex • Chemotaxis- bringing macrophages to the area • Lysis- rupturing membranes • Agglutination • Neutralization

35. “And the Band Played On” reaction • Get out a piece of paper: • Did you know about the AIDS struggles illustrated in the movie BEFORE watching it? • Did you find yourself angry at anytime during movie? When? • Did you find yourself sympathetic at anytime? When? • Did you find yourself sad? When? • Overall view of movie…

36. Memory Cells • Memory T and B cells • Circulate after primary immune response • Body will be able to respond quickly during secondary immune response

37. Natural vs. Artificial Acquired Immunity • Natural: • Through exposure to pathogen • Resistance is the result of primary immune response • Artificial: • Through vaccine injection • Vaccine: bacteria or virus that has been killed or weakened • Contains antigens that stimulate primary immune response • Don’t produce severe symptoms of disease • Ex: Measles, mumps, flu, rubella

38. Active vs. Passive Acquired Immunity • Naturally Acquired Active: • Occurs during pregnancy • Certain antibodies (IgG) pass from maternal blood to fetal blood • Fetus acquires limited immunity against pathogens • Artificially Acquired Passive: • Through injection of antiserum (ready-made antibodies) • Obtain from globulin proteins from people who have already developed immunity against a certain disease

39. Allergic Reactions • Immune response to everyday, non-harmful antigens (allergens) • Types: Delayed and Immediate • Delayed-reaction allergy: • Exposure to allergen on skin • Collects T cells and macrophages in the area • Causes dermatitis

40. Allergic Reactions • Immediate-reaction allergy: • Occurs within minutes • First exposure- B cells become sensitized; IgE is attached to basophils and mast cells • Subsequent exposures- mast cells and basophils secrete several substances including histamine • These substances produce the reactions seen in allergy reactions

42. Transplantation • Transplant tissue or organ • Ex: Organ – liver, kidney, heart; Tissue – skin, bone • New transplant tissue/organ has its own antigens • Recognized as foreign • Starts immune response (which can often reject the new transplant tissue/organ) • Tissue matching helps minimize reaction • Immunosuppressive drugs • Suppress immune reaction, avoid rejection (usually)

43. Autoimmunity • Cytotoxic T cells cannot correctly identify self cells and attacks self cells • Why? • Pathogen borrows self antigens during attack • Pathogen antigen is very similar to a self antigen