1. The Lymphatic System and Immunity A.Pathogen: B. Antigen: C. Lymphatic System: An organism or virus that causes disease. Foreign antigens trigger the immune response. *Antibodies mark antigens or clump them together, making it easy for white cells to destroy them. A system of ducts and nodes that collect, filter, and return fluid that leaked from the *Lymph nodes contain white cells to kill circulatory system. This fluid is called “lymph”. pathogens in lymph. [have antigens (proteins) on surface] Cellular “ID” tags (protein-based)

4. Nonspecific Defense MechanismsSpecific Defense Mechanisms First Line of DefenseSecond Line of DefenseThird Line of Defense  Skin  barrier  Sweat & sebaceous gland secretions are acidic (pH 3-5)  Mucus membranes secrete mucus to trap microbes  Skin and mucus secretions contain lysozyme – enzyme that digests bacterial cell walls  Stomach acid  Chemotaxis - damaged cells release chemokines that attract phagocytes  Phagocytic white cells attack anything foreign that gets past the first line of defense  Neutrophils  Monocytes  Eosinophils (limited phagocytosis)  Natural Killer Cells (kill infected cells)  Inflammatory Response  Damaged cells release histamine (by basophils & mast cells) & prostaglandins that increase blood flow  Pyrogens – released by certain leukocytes to produce fever  Interferons – Released by virus-infected cells to signal other cells, inducing them to produce chemicals that inhibit viral reproduction  Lymphocytes provide specific immunity  produced in marrow  circulate in blood, lymph, spleen, lymph nodes, tonsils, adenoids  B Cells produce anitibodies (humoral response)  T Cells are involved in the cell- mediated response  See Diagram  Passive Immunity  Temporary (borrowed antibodies)  Maternal antibodies through placenta and in breast milk  Active Immunity  Individual makes antibodies after vaccination or infection

6. Leukocytes (White Blood Cells): Neutrophils Monocytes Basophils Eosinophils Lymphocytes B cells: Helper T’s: Killer T’s: *Phagocytes: white blood cells that engulf and digest foreign material. Short- lived phagocytes. Often become macrophages – large, long-lived phagocytes. Release histamines – chemicals that trigger the Inflammatory Response. Release enzymes that destroy pathogen membranes. Make antibodies specific to a particular pathogen Help B cells recognize a particular pathogen. Lyse infected cells

8. Cytotoxic T B Cell Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Free antigens directly activate Infected cells activate Produces Clonal Selection Give rise to Clonal Selection Give rise to First Exposure to Antigen Lyse infected cells Humoral Cell-Mediated

9. APC Cytotoxic T B Cell Memory Helper T Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Engulfed by Macrophage Stimulates Produces Clonal Selection Give rise to Clonal Selection Give rise to Lyse infected cells Humoral Cell-Mediated Helper T Free antigens directly activate Infected cells activate First Exposure to Antigen

13. Memory Helper T Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Produces Second Exposure Stimulates Lyse infected cells Humoral Cell-Mediated Stimulates

14. APC Helper T Cytotoxic T B Cell Memory Helper T Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Free antigens directly activate Engulfed by Macrophage Stimulates Infected cells activate Stimulates Produces Clonal Selection Give rise to Clonal Selection Give rise to Second Exposure Stimulates First Exposure to Antigen Lyse infected cells Humoral Cell-Mediated Stimulates

15. Clonal Selection

17. Cytotoxic T B Cell Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Free antigens directly activate Infected cells activate Produces Clonal Selection Give rise to Clonal Selection Give rise to First Exposure to Antigen Lyse infected cells Humoral Cell-Mediated

18. APC Cytotoxic T B Cell Memory Helper T Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Engulfed by Macrophage Stimulates Produces Clonal Selection Give rise to Clonal Selection Give rise to Lyse infected cells Humoral Cell-Mediated Helper T Free antigens directly activate Infected cells activate First Exposure to Antigen

19. Memory Helper T Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Produces Second Exposure Stimulates Lyse infected cells Humoral Cell-Mediated Stimulates

20. APC Helper T Cytotoxic T B Cell Memory Helper T Plasma Cell Memory B Memory T Active Cytotoxic T Antibodies Free antigens directly activate Engulfed by Macrophage Stimulates Infected cells activate Stimulates Produces Clonal Selection Give rise to Clonal Selection Give rise to Second Exposure Stimulates First Exposure to Antigen Lyse infected cells Humoral Cell-Mediated Stimulates