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Immune System

Immune System. Chapter 43. 2 Types of Immunity. 2 major kinds of defenses have evolved to counter threats of viruses, bacteria, & other pathogens Innate Immunity Present PRIOR to exposure Effective from time of birth Nonspecific Acquired Immunity Present only AFTER exposure

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Immune System

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  1. Immune System Chapter 43

  2. 2 Types of Immunity • 2 major kinds of defenses have evolved to counter threats of viruses, bacteria, & other pathogens • Innate Immunity • Present PRIOR to exposure • Effective from time of birth • Nonspecific • Acquired Immunity • Present only AFTER exposure • Highly specific

  3. Innate Immunity • Barrier Defenses • Cellular Innate Defenses • Inflammatory Response • Natural Killer (NK) Cells

  4. Barrier Defenses • Skin • Provides physical barrier to pathogens • Mucous membranes that cover epithelial linings and surfaces • Physical barrier as well • Secretions that lower skin pH • Lysozymes • Found in tears, sweat, & mucous secretions • Digests bacterial cell walls • Especially effective in eyes & Upper Resp. Tract (URT)

  5. Cellular Innate Defenses 1. Phagocytic White Blood Cells (WBC) or Leukocytes • Neutrophils • Leukocytes that ingest + destroy microbes (phagocytosis) • Most abundant leukocyte • Chemotaxis attracts neutrophils to infected cells • http://en.wikipedia.org/wiki/File:S15-Competitive_Phagocytosis_Assay_in_Collagen.ogg

  6. Cellular Innate Defenses (Page 2) • Eosinophils • Leukocytes that discharge hydrolytic enzymes when in close proximity to parasites (eukaryotic organisms) • Monocytes • Phagocytic leukocytes that develop into macrophages • Macrophages are giant phagocytic cells • Stimulate other immune responses Monocyte

  7. Summary of Phagocytic WBCs • IF a microbe gets past the barriers, phagocytosis may occur • Ingestion of invading microbes by WBCs called phagocytes • Neutrophils • WBCs that ingest & destroy microbes by phagocytosis • Monocytes • Develop into macrophages (giant phagocytic cells) • Eosinophils • Leukocytes that defend against parasitic invaders by secreting hydrolytic enzymes on them

  8. Cellular Innate Defenses (Page 3) 2. Antimicrobial Proteins • Interferon • Innate defense against viral infections • Alter cells adjacent to viral-infected cells to produce substances that inhibit viral replication • Complement System • Leads to the lysis of invading cells • Also play a role in inflammation & acquired defense

  9. Inflammatory Response • Tissue damage due to physical injury (trauma) or pathogen entry • This triggers the release of chemical signals which result in an inflammatory response • Histamine – chemical released in response to injury • Stored in Mast Cells (mastocyte) (found in connective tissues) • Trigger the dilation and permeability of nearby capillaries • Delivers clotting agents & phagocytic cells to the injured area • Fever & septic shock

  10. http://video.google.com/videosearch?sourceid=chrome&q=inflammatory+response&um=1&ie=UTF-8&ei=OweUS6ChJoS0tgfrhsTUCg&sa=X&oi=video_result_group&ct=title&resnum=10&ved=0CDAQqwQwCQ#http://video.google.com/videosearch?sourceid=chrome&q=inflammatory+response&um=1&ie=UTF-8&ei=OweUS6ChJoS0tgfrhsTUCg&sa=X&oi=video_result_group&ct=title&resnum=10&ved=0CDAQqwQwCQ# • Videos 2 & 4

  11. Chemical signals (like histamines) released by macrophages & mast cells at the injury site • Nearby capillaries dilate & become more permeable • Clotting begins • Chemokines attract more phagocytic cells from the blood to the injury site • Neutrophils & macrophages phagocytose pathogens & cell debris

  12. -itis = Inflammatory Response • Appendix  appendicitis • Pancreas  pancreatitis • Meninges  meningitis • Liver  hepatitis • Joints arthritis • Septic shock – overwhelming inflammatory response (systemic) • High fever + Low BP • Most common cause of death in critical care units (CCUs)

  13. Natural Killer (NK) Cells • 4th type of innate immunity • Patrol the body and attack virus-infected body cells • Also attack cancerous cells • Recognize & remove diseased cells • NK releases chemicals that lead to apoptosis • Apoptosis = programmed cell death

  14. Acquired Immunity • Lymphocytes provide SPECIFIC defenses • 2nd line of defense • 2 Types of Lymphocytes (NOT Leukocytes (WBCs)) • B Lymphocytes – B Cells • Proliferate in Bone marrow • Produce antibodies • T Lymphocytes- T Cells • Mature in the Thymus • Helper T-cells (CD4) or Cytotoxic T-cells (CD8)

  15. Acquired Immunity (Page 2) • Lymphocytes circulate through the blood and lymph • Lymphocytes are concentrated in the spleen, lymph nodes, & other lymphatic tissues • Recognize antigens by antigen-specific receptors on their plasma membranes • Antigen – any foreign molecule that elicits a response by lymphocytes • A lymphocyte may have 100,000 receptors, but all of them are specific for only 1 epitope • Epitope – small accessible part of an antigen

  16. Antibodies • Produced by B-cells • When secreted, the antibodies are called immunoglobulins • Part of the humoral immune response • Specific to a given antigen

  17. Epitopes

  18. Activation • Either B- or T-cells can be activated • Occurs when an antigen binds to a B or T cell • Activation leads to each lymphocyte forming 2 types of clonal cells • Clonal cells are all specific to the antigen • 1. Effector cells – combat the antigen • 2. Memory cells – Long-lived & bear receptors for the same antigen • Allows for a quick immune response in the FUTURE

  19. How do B-cells and T-cells Differ? • B-cell receptors bind intact antigens • T-cells bind antigens presented to them by antigen-presenting cells (APC) • B-cell or T-cell responds to only ONE antigen (Specific)

  20. MHC Proteins • Immune system’s way of recognizing “self” cells • Major Histocompatibility Complex molecules (MHC) • Every individual is different in their MHC proteins • MHC proteins bind to an antigen and bring it to the cell surface • Called antigen presentation

  21. MHC Proteins (Page 2) • Two types of MHC proteins • Class 1 MHC – All cells but RBCs • Recognized by cytotoxic T-cells (CD8) • Class 2 MHC – B cells & macrophages • The B cells and macrophages that use Class 2 MHC proteins are called APC (Antigen-presenting cells) • Associated with Helper T-cells (CD4)

  22. Immune Response Types • Primary Immune Response • First exposure to an antigen • Lymphocyte activation • Secondary Immune Response • Antigen in encountered again • Rapid & stronger response

  23. Acquired Immunity • Humoral Immune Response • Involves the activation and clonal selection of effector B cells • B cells produce antibodies that circulate in the blood • Helper T-cells are also involved in the activation of B cells • Cell-Mediated Immune Response • Activation and clonal selection of cytotoxic T cells • Cytotoxic T cells identify & destroy infected cells

  24. Notes on Acquired Immunity • Helper T cell (CD4) • Aids in BOTH responses • Class II MHC on an APC activates the Helper T cells • Secrete cytokines which stimulate BOTH Cytotoxic-T-cells and B-cells • CD4 protein holds helper T-cell to class II MHC • Cytotoxic T cell (CD8) • Binds to Class I MHC • Bound together by the CD8 protein

  25. Comparision • B-cells - produce antibodies (provides humoral immunity) • B-cells produce memory cells and plasma cells • Plasma cells secrete antibodies in huge numbers • Antibodies circulate in blood, then bind & destroy antigen • Cytotoxic T-cells – destroy infected body cells • Helper T-cells – activate both B and T cells

  26. Antibody Actions • Neutralization – Antibodies bind to pathogen’s surface proteins • Prevents pathogen from entering & infecting cells • Opsonization • Results in increased phagocytosis of the antigen • Lysis • Caused by activation of the complement system

  27. Immunities • Active Immunity • Body comes in contact with antigens • Actively produces antibodies in response to antigen presentation • Naturally developed immunity after an infection • Vaccination or immunization • Passive Immunity • Individual receives antibodies • Placental transmission of immunoglobulins (Antibodies)

  28. Show vaccination video • Vaccination Video

  29. Erythrocyte (RBC) Antigens • A, B, AB, or none • Determined by antigen presence on RBC surface • IF non-self, antibodies will form on the foreign antigens • Destroy transfused RBCs

  30. Immune System Pathologies • Lupus, Rheumatoid arthritis, and MS • Immune system fails to recognize body cells • Since these cells are detected as foreign, immune system attacks the body’s own healthy cells • HIV – attacks CD4 cells or Helper-T-cells • Allergies – body over-responds to an allergen • IgE – immunoglobulin E • Histamine & other mediators cause vasodilation and other symptoms • Mast cells mediate the histamine production

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