Introduction To Clinical Immunity PHCL 505 Dr: Wael H Mansy; MD Assistant Professor College of Pharmacy

Mechanisms of protection against infection and disease. Primarily they can be divided into two major categories: 1.non-specific (innate) 2.specific (adaptive) What is the immunity?

Overview of the Immune System Immune System Innate (Nonspecific) 1 st line of defense Cellular ComponentsHumoral Components Adaptive (Specific) 2 nd line of defense Protects/re-exposure Cellular ComponentsHumoral Components Interactions between the two systems

Non-specific Immunity (innate)Specific Immunity (adaptive) Its response is antigen- independent. Its response is antigen-dependent. There is immediate response. There is a lag time between exposure and maximal response. It is not antigen-specific.It is antigen-specific. Exposure does not result in induction of memory cells. Exposure results in induction of memory cells. Some of its cellular components or their products may aid specific immunity Some of its products may help non- specific immunity. Comparison of Innate and Adaptive Immunity

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

Development of the Immune System ery pl mye neu mφmφ lym nk thy CD8 + CD4 + TH2 TH1

Infection and Immunity Balance infection immunity Bolus of infection x virulence immunity Disease =

Beneficial: Protection from Invaders Elimination of Altered Self. Detrimental: Discomfort and collateral damage (inflammation) Damage to self (hypersensitivity or autoimmunity) Effects of the Immune System

Innate (Nonspecific) Immunity

Overview of the Immune System Immune System Innate (Nonspecific) Cellular Components Humoral Components Adaptive (Specific) Cellular Components Humoral Components

Innate Host Defenses Against Infection Anatomical barriers –Mechanical factors –Chemical factors –Biological factors Humoral components –Complement –Coagulation system –Cytokines Cellular components –Neutrophils –Monocytes and macrophages –NK cells –Eosinophils

Anatomical Barriers - Mechanical Factors System or OrganCell typeMechanism SkinSquamous epitheliumPhysical barrier Desquamation Mucous MembranesNon-ciliated epithelium (e.g. GI tract) Peristalsis Ciliated epithelium (e.g. respiratory tract) Mucociliary elevator Epithelium (e.g. nasopharynx) Flushing action of tears, saliva, mucus, urine

Anatomical Barriers - Chemical Factors System or OrganComponentMechanism SkinSweatAnti-microbial fatty acids Mucous MembranesHCl (parietal cells) Tears and saliva Low pH Lysozyme and phospholipase A Defensins (respiratory & GI tract) Antimicrobial Sufactants (lung)Opsonin

Anatomical Barriers - Biological Factors System or OrganComponentMechanism Skin and mucous membranes Normal floraAntimicrobial substances Competition for nutrients and colonization

Humoral Components ComponentMechanism ComplementLysis of bacteria and some viruses Opsonin Increase in vascular permeability Recruitment and activation of phagocytic cells Coagulation systemIncrease vascular permeability Recruitment of phagocytic cells Β-lysin from platelets – a cationic detergent Lactoferrin and transferrin Compete with bacteria for iron LysozymeBreaks down bacterial cell walls CytokinesVarious effects

Cellular Components CellFunctions NeutrophilsPhagocytosis and intracellular killing Inflammation and tissue damage MacrophagesPhagocytosis and intracellular killing Extracellular killing of infected or altered self targets Tissue repair Antigen presentation for specific immune response NK and LAK cellsKilling of virus-infected and altered self targets EosinophilsKilling of certain parasites

Phagocytosis and Intracellular Killing

Characteristic nucleus, cytoplasm Granules CD 66 membrane marker Phagocytes - Neutrophils (PNMs)

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 Characteristics of Neutrophil Granules

Characteristic nucleus Lysosomes CD14 membrane marker Phagocytes - Macrophages

Phagocyte Response to Infection Chemotaxis –N-formyl methionine-containing peptides –Clotting system peptides –Complement products –Cytokines released by tissue macrophages Phagocyte response –Vascular adherence –Diapedesis –Chemotaxis –Activation –Phagocytosis and killing

Attachment via Receptors: IgG FcR Scavenger R Complement R Toll-like R Initiation of Phagocytosis

Phagocytosis Attachment Pseudopod extension Phagosome formation Granule fusion Phagolysosome formation

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

Respiratory Burst Oxygen-Dependent Myeloperoxidase-Dependent Reactions myeloperoxidase OCl - + H 2 OH 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 )

Respiratory Burst Detoxification Reactions H2O2 + O2H2O2 + O2 Superoxide dismutase H 2 O + O 2 Catalase 2O H + 2 H 2 O 2

Effector MoleculeFunction Oxygen-Independent Killing in the Phagolysosome 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

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

Nitric Oxide Dependent Killing IFNγ  TNF Nitric Oxide

Non-specific Killer Cells NK and LAK cells Killer cell Activated macrophages Eosinophils They all kill foreign and altered self targets

Natural Killer (NK) cells ualso known as large granular lymphocytes (LGL) ukill virus-infected or malignant cells uidentified by the presence of CD56 & CD16 and absence of CD3 uactivated by IL2 and IFN-γ to become LAK cells

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

K Cells umorphologically undefined uhave Fc receptor urecognize antibody coated targets ucould be NK cells (IgG), macrophages (IgG), eosinophils (IgE) or other cells (IgG)