Unveiling the Intriguing World of Immune Systems

1. Immune System Professor Nathan A. Swaggner, PhD, MD, JD, ED,Esq,MBA,DPhil. And his lovely assistants Chintan and Jonathan

2. Warm- Up • If you have had chickenpox as a child, you are extremely unlikely to have the disease again. WHY? Be specific.

3. Immune System in Invertebrates • Immune system is non-specific, but it still capable of distinguishing foreign material from normal cells. • If the cells of two sponges of the same specifies are mixed, the cells separate out and reform into two distinct groups. • Earthworms attack tissue grafted from a different earthworm.

4. Plant Immune System • Plants lack antibodies, T-cells, and white blood cells. • Plants do recognize pathogens; triggers a chemical signal that prompts an immune response. • Causes an isolated hypersensitive response that results in programmed cell death (cell suicide or apoptosis).

6. Nonspecific Defenses in Vertebrates • First line of defense • Skin: Intact skin serves as a physical barrier that blocks out most viruses and bacteria • Mucous Membrane: Another physical barrier to pathogen entry • Secretions of skin and mucous membranes: pH of skin is acidic ranging from 3 to 5; secretions contain lysozymes (digests cell walls of bacteria)

7. Nonspecific Defenses in Vertebrates • Second Line of Defense: • White Blood Cells (leukocytes): Phagotysosis (engulfing of pathogens) • Neutrophils – attracted from chemical signals from infected cells • Monocytes- develop into large macrophages (most effective WBC) • Eosinophils- defend against larger parasitic invaders • Attach to cell wall and discharge destructive enzymes

8. http://www.youtube.com/watch?v=JnlULOjUhSQ&list=PL3D7350341CD58E75http://www.youtube.com/watch?v=JnlULOjUhSQ&list=PL3D7350341CD58E75

9. Nonspecific Defenses in Vertebrates • White Blood Cells • Natural Killer (NK) • Destroy virus –infected somatic cells • Mount attack on cell membrane (lyses)

10. http://www.youtube.com/watch?v=HNP1EAYLhOs&list=PL3D7350341CD58E75http://www.youtube.com/watch?v=HNP1EAYLhOs&list=PL3D7350341CD58E75

11. Think Tank • How would an allergic response in an individual be triggered?

12. Inflammatory Responses • Local blood supply increases (causes redness and inflammation) • Histamine • Released by basophil WBC’s in response to tissue injury • Triggers dilation and permeability of nearby capillaries • Prostaglandins • Released by leukocytes and damaged tissue to promote further blood flow

14. Inflammatory Responses • Chemokines • Aids in phagocyte migration to local inflammation • Chemical signals • Pyrogens • Sets the body’s temperature higher • Inhibits growth of microorganisms

15. Antimicrobial Proteins • Complement System • Collection of serum proteins that cause microbes to lyse • Aids in attracting phagocytes to inflammation site • Interferons • Secreted by virus-infected cells • Induces neighboring cells to inhibit viral reproduction

17. Specific Immune Responses • Antigen • specific chemical marker on a pathogen • Epitope • portion of antigen that lymphocyte receptor binds to • Lymphocytes (type of WBC) activated by cytokines secreted by phagocytotes • B: Secretes protein antibodies • Contain antigen receptors on their membrane that are derivatives of antibodies • T: Contain T-cell receptors • Helper T cell: bind to peptides that are class II MHC molecules (derived from materials broken down by phagocytosis) • B Cells and macrophages present foreign materials to helper T cells • Cytotoxic T Cells: Bind to virus-infected cells and cancerous cells that display epitopes that are class I MHC and then destroy the cell

18. Lymphocyte Development • T Cells originate in the thymus • B cells originate in the bone marrow • Through random shuffling of DNA segments, a variety of receptors are produced by lymphocytes • Receptors are tested to make sure they don’t bind to chemical markers in the body’s own tissue

19. Clonal Selection of Lymphocytes • A new antigen is recognized by a receptor on a lymphocyte • Prompt the lymphocyte to make many copies of itself • Two types of copies: • Effector cells- combat current infection • Memory cells: bear the receptors for the same antigen • Memory cells are why the primary immune response at first exposure is much slower than the secondary immune response

20. Humoral Immune Response • Humoral: Foreign Pathogens ingested by phagocytotes (class II MHC) • B Cells Produce antibodies • Some antigens can only activate B cells when helper T cells are also present • Called T dependent antigens • Antibodies bind to antigens on pathogens and neutralize them or cause them to clump together • Clumps are digested by WBC through phagocytosis

22. Think Tank • Why would a virus that infects T cells be particularly harmful?

23. Cell Mediated Responses • Cytotoxic T cells bind to cells infected by viruses or cancerous cells • It kills the target cell by releasing perforin (pores form in target cell membrane) • Pores cause water and ions to flow into the cell and it lyses