1. Prof M.I.N. Matee Office: Microbiology and Immunology Room 19 Phone: 0713-081162 Email: mmatee@muchs.ac.tz

2. Introduction to Immunology Immunology stems from L.- immunis = “exempt;” Eng. = protection from disease *Protective adaptations in higher organisms to rid the body of foreign particles (microbial and otherwise) and abnormal cells Our Immune system involves the interplay between our Non-specific and our Specific Immune responses Non-specific immunities collectively referred to as our Innate immunity Specific immunities are referred to as our Adaptive immunity

8. Innate Immunity

9. Cells of the Immune System Immune System Myeloid Cells Lymphoid Cells Granulocytic Monocytic T cells B cells Neutrophils Basophils Eosinophils Macrophages Kupffer cells Dendritic cells Helper cells Suppressor cells Cytotoxic cells Plasma cells NK cells

10. Innate immunity is the immunity that is immediately available without having to adapt to the specific pathogen that is present. It is not specific to a particular organism such that identical responses can protect against several organisms. Innate immunity is mediated by phagocytes (cell that ingest bacteria or other particulate matter) such as macrophages and neutrophils . It is also mediated by chemical compounds and physical barriers that will be described later.

11. Three Lines of Defense Against Infection

13. Defensins (epithelium) Figure 8.6

14. Progression of Immunity At least three cell types reside within or beneath the epithelium and induce inflammation in response to trauma or microbial products: Macrophages, Mast Cells, and Langerhan’s cells (a skin dendritic cell) Figure 8.5

15. Anatomical Barriers - Mechanical Factors Flushing action of tears, saliva, mucus, urine Epithelium ( e.g. nasopharynx) Mucociliary elevator Ciliated epithelium ( e.g. respiratory tract) Peristalsis Non-ciliated epithelium ( e.g. GI tract) Mucous Membranes Physical barrier Desquamation Squamous epithelium Skin Mechanism Cell type System or Organ

16. Anatomical Barriers - Chemical Factors Opsonin Surfactants (lung) Antimicrobial Defensins (respiratory & GI tract) Low pH Lysozyme and phospholipase A HCl (parietal cells) Tears and saliva Mucous Membranes Anti-microbial fatty acids Sweat Skin Mechanism Component System or Organ

17. Anatomical Barriers - Chemical Factors Opsonin Sufactants (lung) Antimicrobial Defensins (respiratory & GI tract) Low pH Lysozyme and phospholipase A HCl (parietal cells) Tears and saliva Mucous Membranes Anti-microbial fatty acids Sweat Skin Mechanism Component System or Organ

18. Anatomical Barriers - Biological Factors Antimicrobial substances Competition for nutrients and colonization Normal flora Skin and mucous membranes Mechanism Component System or Organ

19. Humoral Components Compete with bacteria for iron Lactoferrin and transferrin Increase vascular permeability Recruitment of phagocytic cells Β -lysin from platelets – a cationic detergent Coagulation system Lysis of bacteria and some viruses Opsonin Increase in vascular permeability Recruitment and activation of phagocytic cells Complement Various effects Cytokines Breaks down bacterial cell walls Lysozyme Mechanism Component

20. Cellular Components Killing of virus-infected and altered self targets NK and LAK cells Killing of certain parasites Eosinophils Phagocytosis and intracellular killing Extracellular killing of infected or altered self targets Tissue repair Antigen presentation for specific immune response Macrophages Phagocytosis and intracellular killing Inflammation and tissue damage Neutrophils Functions Cell

22. Characteristics of Neutrophil Granules primary granules contain cationic proteins, lysozyme, defensins, elastase and myeloperoxidase secondary granules contain lysozyme, NADPH oxidase components, lactoferrin and B12-binding protein azurophilic; characteristic of young neutrophils; specific for mature neutrophils

23. Receptors on Macrophages: LPS receptor-CD14 Toll-like receptors Fc receptors Mannose receptor Complement receptors IFN  receptor Chemokine receptors Figure 1.13 Macrophages phagocytose and degrade foreign particles, bacteria and dead (and dying) host cells.

24. Attachment via Receptors: IgG FcR ScavengerR Complement R Toll-like R Initiation of Phagocytosis

26. Respiratory Burst Oxygen-Dependent Myeloperoxidase-Independent Reactions Toxic compounds – Superoxide anion (O 2 - ), Hydrogen peroxide (H 2 O 2 ), Singlet oxygen ( 1 O 2 ) and Hydroxyl radical (OH*) Pentose-P + NADPH G-6-P-dehydrogenase Glucose +NADP + NADPH oxidase Cytochrome b558 NADP + + O 2 - NADPH + O 2 Superoxide dismutase H 2 O 2 + 1 O 2 2O 2 - + 2H + 2O 2 - + H 2 O 2 OH* + OH - + 1 O 2

27. Respiratory Burst Oxygen-Dependent Myeloperoxidase-Dependent Reactions myeloperoxidase OCl - + H 2 O H 2 O 2 + Cl - 2OCl - + H 2 O 1 O 2 + Cl - + H 2 O Toxic compounds – Hypochlorous acid (OCl - ), and Singlet oxygen ( 1 O 2 )

28. Respiratory Burst Detoxification Reactions H 2 O 2 + O 2 Superoxide dismutase H 2 O + O 2 Catalase 2O 2 - + 2H + 2 H 2 O 2

29. Oxygen-Independent Killing in the Phagolysosome Effector Molecule Function Cationic proteins (cathepsin) Damage to microbial membranes Lysozyme Hydrolyses mucopeptides in the cell wall Lactoferrin Deprives pathogens of iron Hydrolytic enzymes (proteases) Digests killed organisms

30. Summary of Intracellular Killing Pathways Intracellular Killing Oxygen Dependent Oxygen Independent Myleoperoxidase Dependent Myleoperoxidase Independent

31. Nitric Oxide Dependent Killing IFN γ  TNF TNF Nitric Oxide Nitric Oxide

34. Lymphokine Activated Killer (LAK) cell IL2 IFN IFN IL2 kills malignant cells kills transformed and malignant cells

36. Cells, tissues and organs I. Cells B. mononuclear cells: monocytes, macrophages monocytes – in blood macrophages – larger, more organelles receptors for antibody and complement two populations – fixed and wandering

37. Cells, tissues and organs I. Cells C. granulocytes PMN irregular nucleus, 2-5 lobes many granules, differ in staining properties 1. basophils – granules stain with basic dyes two-lobed nucleus non-phagocytic secrete vasoactive agents (histamine, serotonin, prostaglandin) affinity for IgE – coats surface of the cell triggers cell to secrete vasoactive agents hayfever, asthma, exzema

38. Cells, tissues and organs I. Cells C. granulocytes PMN 2. eosinophils – granules stain with acidic dyes two-lobed nucleus, connected by thin strand migrate to tissues defend against protozoa and helminths release cationic proteins & oxygen metabolites damage parasite’s membrane 3. neutrophils – granules stain at neutral pH 3-5 lobed nucleus receptors for antibody & complement migrate to site of tissue damage/infection major phagocytes many hydrolytic enzymes – digestion O 2 -dependent & O 2 -independent paths

39. Cells, tissues and organs I. Cells C. granulocytes PMN 4. mast cells in connective tissue granules of histamine, pharmacological agents contribute to inflammatory response allergies and hypersensitivities

40. Chemical barriers (below skin & mucous membranes) fibronectin – glycoprotein binds bacteria to block attachment, enhance removal β -lysin – cationic polypeptide from platelets disrupts Gram-positive cell’s membrane interferon – family of glycoproteins block viral mRNA transcription enhance destruction of ‘infected cells’ intracellular parasites ( Rickettsia & Chlamydia ) tumor necrosis factor alpha (TNF- α ) secreted by phagocytes & some T cells in response to LPS, M . tuberculosis , etc. activates macrophages involved in inflammatory response complement – later

41. Barriers – Chemical Chemical barriers (below skin & mucous membranes) complement – heat-labile component of blood family of serum proteins participate in immune response, specific and non-specific mediate inflammation enhance cytolysis, on antibody-coated cells activate phagocytosis complement cascade activation of one factor activates others three pathways classical – specific immune response (later) lectin pathway alternative pathway

42. Inflammation or inflammatory response generalized response to tissue damage (scrape, bite) mediators: histamine, kinins, 5-hydroxytryptamine four signs/symptoms erythema (rubror) edema (tumor)– IgG, complement, etc., to tissues pain (dolor) – tissue distension warmth (calor) – slight temperature elevation (LOCAL) clot to wall off area inflammatory mediators: histamine, leukotrienes, bradykinin, prostaglandin capillary endothelium activated attract/catch neutrophils dilate to increase permeability, blood supply

43. Chronic inflammation two weeks or longer duration dense infiltration by lymphocytes and macrophages cause tissue damage granuloma forms, due to continual presence of pathogens or large antigen-antibody compleses new connective tissue formed

44. Phagocytosis opsonin-dependent – mediated by antibodies or C3b recognized by phagocytes

45. Phagocytosis opsonin-independent variety of non-specific & specific receptors on phagocytes lectin – carbohydrate binding protein protein-protein binding

46. Cytokines immunoregulators – soluble proteins/glycoproteins intercellular mediators, intracellular meditors monokines – from mononuclear phagocytes lymphokines – from T lymphocytes interleukins – from leukocytes, act on other leukocytes colony-stimulating factors (CSF) – stimulate immature leukocytes in bone marrow

47. Interferon family of glycoproteins block viral mRNA transcription enhance destruction of ‘infected cells’ intracellular parasites ( Rickettsia & Chlamydia )

48. Fever elevation of body temperature prostaglandin targets hypothalamus heat conservation mode – decrease circulation to skin heat generation mode – shivering heat dissipation mode – increase circulation to skin sweating aspirin inhibits prostaglandin release

49. Figure 8.10 **

50. Figure 8.14

51. Natural killer (NK) cells are lymphocytes the can kill host cells (e.g., virus infected cells) without making their own antigen-specific receptor (do not require ab or TCR)(innate immunity) Once referred to as large grauular lymphocytes or LGLs

52. Natural killer cells (NK) large, non-phagocytic granular lymphocytes non-T, non-B lymphocytes lack target cell specificity 1. antibody-dependent cell-mediated cytotoxicity possess FC receptor 2. surface receptor-mediated cytotoxicity target cells lacking MHC I

53. Natural Killer cells 1. antibody-dependent cell-mediated cytotoxicity possess FC receptor

54. Natural killer cells 2. surface receptor-mediated cytotoxicity target cells lacking MHC I