Lymphatic System: Structures & Immune Response

1. Lymphatic System:Structures & Immune Response Honors Anatomy & Physiology Wbc engulfs bacteria: http://www.youtube.com/watch?v=JnlULOjUhSQ

2. Lymphatic vessels – drainage of excess interstitial fluid (lymph) that is returned to blood vessels • Lymphatic capillaries weave between tissue cells and blood capillaries in areolar tissue • Very permeable • Lacteals – specialized capillaries found in villi of intestinal mucosa to help absorb fats • Flows to collectively larger vessels Lymph Vessels

3. Right lymphatic duct • Right arm, side of head and upper thorax • Empties into the right subclavianvien • Thoracic duct • Much larger • Rest of the body • Empties into junction of left subclavian vein & jugular vein • About 3L enters blood every 24 hours Lymphatic Vessel Drainage

4. Lymphatic ducts get clogged with parasitic roundworms • Swelling of lower limbs and scrotum due to edema What is elephantiasis?

5. Filters lymph fluid • Macrophages destroy microorganisms • Help activate the immune system • Lymphocytes monitor & attack antigens • 100’s of these small organs • Bean shaped • <1inch long • Cortex (outer region) • Dividing B cells • Circulating T cells • Medulla (inner region) • Plasma cells • macrophages • Fewer efferent lymph vessels than afferent vessels Lymph Nodes

6. Spleen – monitors blood • Red pulp -extracts aged & defective blood cells • Stores hemoglobin & platelets (recycled) • White Pulp -contains lymphocytes & macrophages • Thymus – T cells become immunocompetent (specific) • Atrophy after puberty (replaced by adipose tissue) • Does not directly fight pathogens • Tonsils – invaginations trap pathogens • Contains lymphocytes & macrophages • Palatine tonsils • Lingual tonsils • Pharyngeal tonsil • Tubal tonsils Lymph Organs

7. MALT: Mucosa Associated Lymphatic Tissue • Protects passages open to exterior • Produces memory cells against invaders • Includes: • Peyers Patches • Clusters of lymph tissue on small intestine • Appendix • Off shoot of large intestine • Destroys any bacteria may leave intestine Lymphatic Tissues

8. 1st line defense- Surface Barriers: • Skin & Mucous Membranes • Physical barrier • Acidity of skin secretions (ph 3-5) • Sebum – toxic to bacteria • HCl of stomach • Saliva & lacrimal fluid contain lysozyme • Enzyme destroys bacteria • Mucus traps microorganisms Innate (Non Specific) Defenses

9. Cells • Phagocytes – engulfs & digests • Macrophages from WBC monocytes • Free (mobile) or fixed (liver, brain) • Neutrophils (WBC) • Become phagocytic after encounters pathogen • Destroy self in process • Eosinophils (WBC) • defend against parasitic worms • Natural Killer (NK) Cells • “police” blood & lymph • Detect lack of “self” antigens • Direct contact induces target cell to undergo apoptosis • Lyse & kill cancer cells & viral infected cells Innate (Non Specific) Defenses (20 Defense)

10. Chemicals • Inflammation -Prevents spreading of pathogen & disposes pathogens & cell debris • Redness & heat • Mast cells release histamines causing vasodilatation • Swelling & pain • Increased permeability of capillaries • Clotting factors, antibodies & fluid leak into tissues • Antimicrobial proteins • Interferons (IFNs) • Secreted by viral infected cells to prevent other cells from becoming infected • Stimulate synthesis of proteins that interfere w/viral protein synthesis (not specific) • Fever • Response to widespread infection • Macrophages and WBC releasepyrogens • Chem that resets thermostat in Hypothalmus • Increases metabolism Innate (Non Specific) Defenses

12. Must be primed by initial exposure before it can defend against it 3 important features: • Specific against a particular pathogen • Systemic – not restricted to infection site • Humoral Immunity – circulating antibodies in body fluids • Cell Mediated Immunity – lymphocytes attack pathogens • Memory – recognizes and mounts strong attacks against previously encountered pathogens Adaptive Defenses (Specific)

13. Antigens – Foreign substances that provoke an immune response • Non-self - not normally found in the body • Cause proliferation of lymphocytes & antibodies • Self-Antigens • MHC (major histocompatibility complex) proteins on surface of “self” cells • Variety - genetically determined Antigens

14. AKA immunoglobulin (Igs) • Secreted by B cells or plasma cells • Structure: • ‘Y’ shaped; 4 polypeptide chains (2 Heavy, 2 Light) • Variable region – 2 binding sites that responds to specific antigens • Constant region – determines Ig class • Antigen-antibody complex: • Neutralizes - no longer harmful • Agglutination – cross linked causing clumping • Inactivates pathogens and tags for destruction Antibodies

16. Antigen binding to receptor on specific B lymphocyte stimulates proliferation forming clones that differentiate into: • Plasma cells – secrete 2,000 antibodies per second (for about 5 days then dies)!!! • Memory cells – will respond to subsequent exposures to same antigen Humoral Immune Response

17. Contain dead or attenuated (weakened) pathogens or their components • Spares us symptoms of disease that would normally occur during a primary response • Memory cells are formed against antigen (humoral only) How do Vaccines work?

18. T cells mature in Thymus • Targets infected cells, cancer cells, foreign tissues • Helper T cells (CD4) • Stimulates production of cytotoxic T cells and B cells, activates macrophages, and releases cytokines (chemicals that trigger proliferation and inflammation) • Cytotoxic T cells (CD8) • Binds to infected cells and inserts chemicals causing apoptosis • Regulatory T cells • Suppresses immune activity • Memory T cells • Responds quickly to subsequent infections (last years) • Double recognition on an antigen presenting cell: • Non self antigen • MHC proteins indicating “self” cell Cell Mediated Response

19. Innate – genetically determined • Acquired – arises during life • Active – appears after exposure to antigen • Naturally- continually induced as encounter “new” pathogens or antigens • Induced – stimulated under controlled conditions • Vaccine: dead/inactive pathogen that induces an immune response • Passive – transfer of antibodies from another source • Naturally – mother to baby • Gestation – via placenta • Infancy – via breast milk • Induced – antibodies administered to fight infection or prevent disease after exposure Types of immunity

20. Create a comic strip depicting the specific response of lymphatic system (combating a pathogen of your choice) • Write a script for a mini-play describing specific response of lymphatic system • May work in pairs • Either choice should include: B cells, plasma cells, antibodies, helper T cells, cytotoxic T cells, memory cells, suppressor (regulator) T cells, and macrophages Select your Task…