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Immune System

Immune System. Chapter 43. Introduction to the Immune System. The human body must defend itself against unwelcome intruders. It must also deal with abnormal body cells, which, in some cases, may develop into cancer. Two major kinds of defense have evolved to counter such threats.

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Immune System

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  1. Immune System Chapter 43

  2. Introduction to the Immune System The human body must defend itself against unwelcome intruders. • It must also deal with abnormal body cells, which, in some cases, may develop into cancer. • Two major kinds of defense have evolved to counter such threats. • Innate Defenses • Acquired Defenses

  3. Overview of the Immune System

  4. External Barriers: • intact skin epidermis • Acid mantle of skin • Keratin • Intact mucous membranes • Mucus • Nasal hairs • Cilia • Gastric juice • Acid mantle of vagina • Lacrimal secretion • Urine • Oil (sebum) secretions

  5. Internal Cellular Defenses: • Phagocytic cells • Neutrophils • Monocytes • Eosinophils • Dendritic cells

  6. Internal Cellular Defenses

  7. Phagocytic Responses • Pseudopodia • Ingestion • Vacuole • Fuse with lysosome • Digestion • Exocytosis

  8. Internal Cellular Defenses: • Natural Killer Cells • Non-specific • Perforins • Apoptosis

  9. Natural Killer (NK) Cells (Cytotoxic lymphocyte) • Promote cells lysis by direct cell attack against virus-infected or cancerous body cells • Referred to as null third population cells that are spontaneous non antigen recognizing. • Lack surface antigen receptors but recognize certain surface sugars on infected or cancerous cells • Release cytolytic chemicals (perforins) that attack a targets cell's cell membrane and bore hole. Granzymes are released and cellular enzymes disrupted. • Present in spleen, lymph nodes, red bone marrow, and blood

  10. Inflammatory Response

  11. Inflammatory Response • Cardinal signs of inflammation redness, pain, heat and swelling • Local versus systemic inflammation • Septic shock

  12. Interferons - proteins that diffuse to nearby cells, where they stimulate the synthesis of a protein known as PKE, which then interferes with viral replication in those cells by blocking protein synthesis at the ribosomes • Gamma interferon - produced by lymphocytes, mobilizes and activates macrophages and NK cells, stimulates synthesis and expression of more class I and II MHC, and enhances activity of B cells and cytotoxic T cells • Alpha interferon - produced by most leukocytes, mobilizes and activates macrophages and NK cells • Beta interferon - produced by fibroblasts, mobilizes and activates macrophages and acts to reduce inflammation

  13. Complement - twenty plasma proteins that amplify the inflammatory response, lyses microorganisms and enhances phagocytosis by opsonization. Two pathways: classic and alternative. • Pyrogens - secreted by macrophages and signal the body to increase temperature; high body temperature inhibits microbial multiplication and enhances body repair processes.

  14. Antigen (Ags) • Antigens are substances that can mobilize immune system and provoke a response • Are considered nonself • ii. Nonself Antigens • Types: • Complete antigen - functional properties: • immunogenecity - stimulate B and T cell formation and antibody production • reactivity - react with B and T cells

  15. Small antigens (peptide, nucleotide, hormones) - may bind to body's own biological molecules (proteins); antigen when bound to body's own molecules may cause an immune response, this is called an allergy. Small antigens are calledhaptens (incomplete antigen) and alone are not immunogenic. • Reactivity (immune response) is dependent upon antigen structure; localized regions, antigenic determinants are where antibodies or B and T lymphocytes can bind. • iii. Self Antigens • Are not foreign or antigenic to us, but are strongly antigenic to other individuals • egs. blood transfusions and organ transplants

  16. Major Histocompatibility Complex (MHC) antigens Found on all cells except RBCs • Involved in tissue recognition (aids in transplantation recognition) • Two types of MHC antigens: MHC class I found on all body cells • MHC class II found on antigen present cells • Antigen Presentation Ingestion of the antigen • Digestion of antigen into peptide fragments • Fusion of vesicles (peptide fragments with MHC-II molecules) • Binding of peptide fragments to MHC-II molecules • Insertion of antigen-MHC-II complex into plasma membrane

  17. ACQUIRED IMMUNITY • All cells have cell surface macromolecules • Adaptive immunity is sensitive to specific infections • Antigens distinguish self versus non-self

  18. ACQUIRED IMMUNITY

  19. ACQUIRED IMMUNITY

  20. Humoral Immunity • Also known as antibody-mediated immunity • Utilizes B-lymphocytes • Recognizes antigen directly • Made in the bone marrow

  21. Clonal Selection and Proliferation

  22. Antibody Structure

  23. Antibody Classes

  24. Antibody Classes

  25. Antibody Functions

  26. Cell-Mediated Immunity • Utilizes T-lymphocytes • T-cells are made in the bone marrow but mature in the thymus gland. • Cannot recognize antigens directly

  27. Cell-Mediated Immunity CLASS I MHC PROTEIN CLASS II MHC PROTEIN

  28. Helper T-Lymphocyte Stimulation

  29. Helper T-cells stimulate B-cells

  30. Cytotoxic T-Lymphocyte Stimulation

  31. Overview of Adaptive Immunity

  32. Adaptive Immunity

  33. Problems with the Immune System • Blood Transfusion Reaction • Tissue Rejection • Allergies • Autoimmune disease • Immunodeficiencies

  34. Blood Transfusion Reactions

  35. Rhesus Factor

  36. Tissue Transplant and Rejection • Autograft • Isograft • Allograft • Xenograft

  37. Allergies or Hypersensitivities • Type I • Type II • Type III • Type IV

  38. Autoimmune Diseases • Multiple sclerosis • Rheumatoid arthritis • Systemic lupus • Grave's disease • Type I diabetes mellitus

  39. Immunodeficiency Diseases • Primary Immunodeficiency • a.k.a. “inborn” • SCID • Secondary Immunodeficiency • a.k.a. “acquired” • Drugs • Stress and Hodgkin’s • AIDS

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