Categorization and Actions of Leukocytes

1. Categorization and Actions of Leukocytes Sandy Su Hon Lum Adriana Too Linda Zhang Wendy Chen PHM142H1 September 25th 2013 PHM142 Fall 2013 Instructor: Dr. Jeffrey Henderson

2. What Are Leukocytes? • White blood cells • Primary cells responsible for the body’s defense against infectious diseases and foreign antigens • Originate from bone marrow and circulate within the bloodstream • Larger than RBCs but much less abundant • Amount found in blood can be indicator of disease

3. Types of Leukocytes • Basophils • Eosinophils • Neutrophils • Monocytes/Macrophages • Lymphocytes • B-lymphocytes • T-lymphocytes • Natural killer cells (NK cells)

4. Morphological Characterization • Granulocytes • Cells that contain granules (small secretory vesicles) • Granules contain chemicals required for triggering actions from other leukocytes • Includes: • Basophils • Eosinophils • Neutrophils

5. Functional Characterization • Phagocytes • Cells that engulf or ingest their targets via phagocytosis • Includes: • Eosinophils • Neutrophils • Monocytes/Macrophages

6. Functional Characterization • Cytotoxic cells • Kill cells that present foreign antigens by the release of chemicals • Includes: • Eosinophils • Some lymphocytes

7. Functional Characterization • Antigen-presenting cells (APCs) • Specialized cells displaying foreign antigens on cell surface via major histocompatibiity complex (MHC) Class II • Exogenous (foreign/non-self) antigens • Includes: • Monocytes/Macrophages • One type of lymphocyte

8. Basophils • Rarest leukocyte in circulation • Granules contain: • Heparin to prevent blood clotting • Histamine to cause vasodilation and increase vasopermeability • Involved in allergy and inflammatory responses

9. Eosinophils • Most functioning in mucosal surfaces • Phagocytic, cytotoxic, and contains granules • Attach to antibody-coated parasites and release toxic substances • Contribute to allergy, inflammation, and tissue damage

10. Neutrophils • Most abundant type of leukocyte • First of circulating leukocytes to arrive at infection site • Phagocytic cells that ingest foreign bacteria • Granules fuse with phagosomes to kill ingested material • Secrete various chemical mediators involved in inducing fever and inflammatory responses

12. Monocytes/Macrophages • Monocytes circulate in the blood and are precursors to macrophages • Macrophages are phagocytes and APCs acting as primary scavengers • Present foreign antigens to activate helper T cells • Secrete chemicals that induce fever, promote inflammation, and reinforces activation of T-lymphocytes

13. Inflammatory response fever macrophages Ingest & kill activate cytokines secrete activate pathogens activate bind antibodies helper T cells Clonal expansion active helper T cells memory helper T cells

14. Lymphocytes • B-lymphocytes are activated when: • They recognize specific foreign antigens • Antigen-specific active helper T cells are present • B-lymphocytes differentiate into: • Plasma cells • Actively produce antigen-specific antibodies • Memory B cells • Remains inactive in blood until next exposure to their specific antigen • Faster and larger immune response

15. Lymphocytes • T-lymphocytes develop into: • Helper T cells • Help activate B and other T lymphocytes by binding to APCs and releasing cytokines • Cytotoxic T cells • Recognize and kill host cells with foreign antigens (i.e. Infected cells) by secreting digestive enzymes and inducing apoptosis in target cell • Secrete perforin which causes pores to form on targeted cell

16. Inflammatory response macrophages fever activate cytokines secrete pathogens activate presents antigen bind antibodies helper T cells virus infected cells secrete activate cytotoxic T cells B cells Clonal expansion Clonal expansion Clonal expansion kill active helper T cells memory helper T cells active cytotoxic T cells memory cytotoxic T cells memory B cells plasma cells activate

17. Lymphocytes • Natural killer cells • When activated attack and destroy abnormal host cells (i.e. virus infected cells and cancerous cells) • Use smiliarcytotoxic mechanisms to cytotoxic T cells

18. Legend: Formed elements of circulating blood Tissue cells Pluripotent Stem Cell Lymphoid stem cell Myeloid stem cell T-lymphocyte (T cell) Natural killer (NK) cell Eosinophil Neutrophil B-lymphocyte (B cell) Basophil Monocyte Macrophage Plasma cell

19. Inflammatory response macrophages fever eosinophils neutrophils activate Ingest & kill basophils activate cytokines secrete activate pathogens natural killer cells activate activate bind antibodies kill helper T cells virus infected cells secrete activate cytotoxic T cells B cells Clonal expansion Clonal expansion Clonal expansion kill active helper T cells memory helper T cells active cytotoxic T cells memory cytotoxic T cells memory B cells plasma cells activate

20. Summary • Basophils = granulocytes that release chemicals to promote inflammation • Eosinophils = granulocytes, cytotoxic killers that primarily target parasites • Neutrophils = phagocytic granulocytes that ingest and kill bacteria • Monocytes/macrophages = phagocytic antigen-presenting cells that ingest pathogens and activate helper T cells • B-lymphocytes = antigen specific cells that have NOT come in contact with their antigen • Plasma cells = activated B lymphocytes that have been in contact with their antigen and produces specific antibodies • Memory B cells = inactive B lymphocytes that have been in contact with their antigen and remains in body in the event of secondary exposure to same antigen • Helper T cells = lymphocytes that release cytokines to help activate B lymphocytes • Cytotoxic T cells = lymphocytes that kill self cells carrying foreign antigens by inducing apoptosis and secreting digestive enzymes and perforin • Natural killer cells = lymphocytes that target abnormal self cells and induces apoptosis

21. References Derrickson, B., Tortora, G.J. (2012). Principles of Anatomy and Physiology. New Jersey: John Wiley & Sons, Inc. Doan, T., Melvold R., Viselli, S. Waltenbaugh, C. (2007). Immunology. New York: Lippincott Williams & Wilkins. Murphy, K. (2012). Janeway’sImunobiology. (8thed). New York: Garland Science. Silverthorn, D.U. (2009). Human Physiology: An Integrated Approach (5thed). San Francisco: Pearson. Alberts, B., Johnson, A., Lewis, J., et al. (2002). Molecular Biology of the Cell (4thed). New York: Garland Science