Immune System

1. Immune System Chapter 43

3. 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

4. Overview of the Immune System

6. 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

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

8. Internal Cellular Defenses

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

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

12. 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

13. Inflammatory Response

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

17. 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

19. 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.

20. 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

21. 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

23. 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

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

26. ACQUIRED IMMUNITY

27. ACQUIRED IMMUNITY

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

30. Clonal Selection and Proliferation

31. Antibody Structure

32. Antibody Classes

33. Antibody Classes

34. Antibody Functions

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

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

37. Helper T-Lymphocyte Stimulation

38. Helper T-cells stimulate B-cells

39. Cytotoxic T-Lymphocyte Stimulation

40. Overview of Adaptive Immunity

41. Adaptive Immunity

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

43. Blood Transfusion Reactions

44. Rhesus Factor

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

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

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

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