The Lymph and Immune System

1. The Lymph and Immune System Defense Against Infectious Disease

2. Pathogens • Defined as any living organism or virus that is capable of causing disease is called a pathogen • Include • Viruses • Bacteria • Protozoa • Fungi • Various worms

3. The Lymphatic System • Consists of two semi-independent parts • Lymphatic vessels • Lymphoid tissues and organs • Lymphatic system functions • Transport fluids back to the blood • Play essential roles in body defense and resistance to disease

4. The Lymphatic System • Lymph – excess tissue fluid carried by lymphatic vessels • Properties of lymphatic vessels • One way system toward the heart • No pump • Lymph moves toward the heart • Milking action of skeletal muscle • Rhythmic contraction of smooth muscle in vessel walls

5. The Lymphatic System • Lymphatic collecting vessels • Collects lymph from lymph capillaries • Carries lymph to and away from lymph nodes

6. Lymphatic Organs • Several other organs contribute to lymphatic function • Spleen • Thymus (sweet breads) • thymosin • Tonsils • Peyer’s patches

7. Preventing Pathogens from Entering the Body • Non-Specific Immune Mechanisms • Skin • Primary outer defense • Dermis layer contains phagocytes • Stomach acid • Acidic environment kills most pathogens • Mucous membranes • Goblet cells create mucus and enzyme called lysozyme • Saliva and lacrimal glands produce lysozyme too

8. If/When Pathogens Get In: Specific (i.e., Immune System) • Homeostatic Imbalance or Illness: Viral/Bacterial load exceeds the body’s ability to defend • White Blood Cells (WBC’s/Phagocytic Leukocytes) • Macrophages are 1st line of defense • Identify “self” or “non-self” via protein identification (antigens) • Called a non-specific response

9. Antibody Production • Produced by B lymphocytes in response to a specific pathogen • All pathogens have unique antigen combinations on the surface of their cells • Antibodies are ‘Y’ shaped protein molecules that have binding sites for these specific antigens on the open end • Antibodies bind to pathogen • Identifies it for disposal by body • Does not allow it to reproduce (bacteria) or bind to host cell (virus)

10. Steps of Immune Response (vaccination/immunizations) • 1. A specific antigen type is identified • 2. Specific B lymphocyte is identified that will produce an antibody that will bind to antigen • 3. B lymphocyte and other identical B lymphocytes rapidly clone themselves (mitosis) to increase lymphocyte count • 4. Lymphocytes begin antibody production • 5. Antibodies circulate in blood to find antigen match • 6. Antibodies attach and help eliminate pathogen • 7. Some antibodies remain in bloodstream and provide immunity (memory cells)

11. HIV, AIDS and the Immune System • Human immunodeficiency virus (HIV) has antigen binding site that binds to helper-T cells • Helper-T cells communicate via bloodstream as to which cells need to undergo cloning in order to begin antibody production • Without helper-T cells, antibody production cannot take place and no immunities develop • Secondary infections cause Acquired Immunodeficiency Syndrome and eventual death

12. Types of Immunities • Active • Production of antibodies by organism itself • Passive • Acquisition of antibodies from another organism • Natural immunity • Immunity due to infection/acquisition from mother • Artificial • Due to vaccine inoculation/antibodies

13. Antibiotics v. Bacteria and Viruses • Antibiotics are chemicals that take advantage of the differences between prokaryotic and eukaryotic cells with respect to the chemical pathways within the cell • Some block protein synthesis in prokaryotic cells but eukaryotic cells (yours) • Others inhibit bacterial cell walls • For these same reasons, viruses are not affected because they utilized out eukaryotic cells for replication • Cytotoxic T-cells • Destroy virus infected cells in the body • Interferon