Lecture 16

1. Lecture 16 Lymphatic System and Immune Response Anatomy and Physiology JPHubbard Hartnell College – Bio11

2. Drain excess interstitial fluid & plasma proteins from tissue spaces • Transport dietary lipids & vitamins from GI tract to the blood • Produce, maintain and distribute lymphocytes

3. Components of Lymphatic System • Lymph • similar to interstitial fluid • Vessels • Blind ended • Organs • red bone marrow • thymus • spleen • lymph nodes • Diffuse Tissues • tonsils, adenoids & peyers patches

4. Lymphatic Vessels • Capillaries – similar to veins • Specialized to gather tissue fluid • In GI tract, known as lacteals -- contain chyle • Drain through series of trunks to 2 ducts: • Right lymphatic duct: right side head, arm & chest (above diaphragm) • Thoracic duct: Rest of body

6. Lymphedema: swelling and consequent distention of tissue to blockage of lymphatic vessel

7. Lymph Nodes • Fibrous connective covering = capsule • Fibrous partitions = Trabecula • Hilus: point of entry of blood vessels, efferent lymphatic vessel • Afferent vessels enters opposite hilus through cortex • Cortex and Medulla harbor various sorts of immune cells – site of development of specific immune response • Concentrated in different regions

9. Distribution of Lymph Nodes – major areas • Cervical – head/neck • Axillary – upper limbs, mammary in F. • Popliteal – thigh and leg • Inguinal – from lower limbs • Thoracic – lungs, resp. and mediastinal strs. • Also - Nodules: Associations with digestive tract/pharynx

10. Lymphatic Nodules • scattered throughout connective tissue of mucous membranes = mucosa-associated lymphoid tissue (MALT) • Peyer’s patches in the ileum of the small intestine • Appendix • Tonsils form ring at top of throat • adenoids (pharyngeal tonsil) • palatine tonsils (on each side wall) • lingual tonsil in the back of the tongue

11. Fig. 14.08

12. Other Lymphatic Organs • Spleen • Lateral to stomach • Site of • exposure of blood to populations of immune cells • Destruction of erythrocytes • Thymus • superior to heart in mediastenum • Site of maturation and production of hormones which stimulate maturation of T-lymphocytes • Decreases in mass after adolescence

13. Spleen • Largest lymphoid organ in body • The spleen serves two major functions in the body: • 1. It is responsible for the destruction of old red blood cells (RBC) • 2. It is a major site for mounting the immune response. The spleen behaves similarly to a lymph node but instead of filtering the lymphatic fluid it filters the blood.

14. Disease and Immunity • Pathogenesis: Process by which a pathogen causes disease • Virus: Invade and subvert host cell metabolic processes, damage cells • Bacteria, Fungi, Protozoans: Produce toxins, direct tissue damage (enzymes) • Worms: release toxins, feed off blood, compete with host for food • Prions: misfolding of host proteins • Resistance: 2 levels • Innate/nonspecific • Adaptive/specific

15. Innate Defenses • Passive: • Mechanical barriers • Chemical barriers • Active: • Interferons – hormone-like produced in response to virus infection • Fever • Inflammation • Defense cells • Phagocytes • Neutrophils, monocytes – become active in tissues • Macrophages: fixed in certain organs • Natural killer cells

16. Nonspecific Defenses – Surface Barriers

18. Natural Killer Cell at work – hole in cancer cell

19. Complement proteins (~ 20 different ones) • Stimulation • Non-specific – by presence of foreign invader • Specifically – by interaction with antigen specific antibodies • Functions: • Stimulate histamine release • Promote phagocytosis • Kill bacteria through formation of membrane attack complex • Enhance inflammation

21. Pathogen Specific Active Responses • Two Important Characteristics: • Specific • Response to specific antigen or hapten • Memory • Basis for immunization • Development of two cell lines • B-cell line • T-cell line

22. Two Cell Lines – Specific Response • T-cells: produced bone marrow, mature in thymus • produce specific cytotoxic cells • like natural killer cells – but specific • Cell mediated response • B-cells: produced/mature in bone marrow • specific antibodies (immunoglobulins) • Humoral response

23. Specificity Body reacts to: • Antigens – a foreign substance • Protein, Glycoprotein, smaller molecules (hapten) bound to larger molecules • Toxins (poisons) • Molecules unique to microorganisms that are not associated with human cells • Altered major histo-compatibility proteins (MHC protein) identify self (‘Flag’ – friend/foe recognition) • 10 million  1 billion different antigens may be recognized • See: http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/prostruct/toll/toll.html

24. How the specific response is developed: • Antigen digested by macrophages / binds Virgin B cell • Macrophage • Acts as antigen presenting cell • Sends chemical signals which stimulate Helper T-cells division • Helper T cells + antigen (or antigen-MHC complex) activates multiplication of: T cell line  cytotoxic T cells B cell line  plasma cell production of Memory B and T cell lines

25. Fig. 14.13 P371-372

26. Clonal Selection Theory • Diverse B lymphocytes produced during fetal development • Body harbors diverse population of capable of producing specific antibody w/o ever being exposed to particular antigen • Encounter with antigen stimulates multiplication of specific cell line; a clone from ancestral cell • All descendents produce same antibody

27. Role of T cells in defending the body • Act like natural killer cells – but they are specific • Act primarily on cells • Kill • virus infected cells • Cancer cells • bacteria

29. Role of B cells in Defending Body • Produce antibodies – humoral response • Antibodies bind to foreign antigen • either free or on cell surface • Binding may destroy antigen directly, make it a better target for phagocytes • Examples: • Toxins produced by pathogens • Bind bacteria, fungi, protozoan pathogens

30. Antibodies • 5 types – • IgG – main type of antibody involved in response to disease – • Other types: • IgM – involved in activation of complement • IgA – certain secretions, protection of digestive and resp. epith. • IgD – found on surface of virgin B cells • IgE – association with mast cells – allergic response and certain parasites

31. How your immune system ‘remembers’: • Two memory cell lines are produced: • Memory T cells • Memory B cells • Long lived – ready to stimulate immune system to respond rapidly if the same pathogen shows up again • Produce effector B and T cell lines

33. Induced Immunity – Active vs. Passive • Passive Immunity – occurs when individual given antibodies formed in another organism • Active Immunity – results in activation of body to produce its own antibodies – B and T cell lines • Primary immune response – • results in lower and transient titre • Important in elicitation of secondary response

35. Allergies - Immune System out of Control? • Excess IgE antibodies produced • IgE antibodies bind to mast cells – • IgE antibodies interact with allergen and release histamine • Histamine causes swelling of blood vessels, fluid leakage • Type of response depends on where reactions occur and degree of reaction

36. The End. http://marie.guibert.chez.tiscali.fr/html/illsc.html