Innate immunity Properties of innate immunity Components of innate immunity –Epithelial barriers –Cellular mechanisms –Humoral mechanisms Role of innate immunity in stimulating adaptive immune response

Principle mechanisms of innate and adaptive immunity

Mechanisms of innate immunity - phylogenetically older - exist before or react immediately after contact with pathogen - first line of defense - are not enhanced upon repetead contact with pathogen (no memory) - react predominantly to infectious agents - stimulate and shape adaptive imunity

Components of innate immunity - epithelial barriers (skin and mucosal membranes) - humoral components (complement, cytokines etc.) - cells (phagocytes, NK cells...)

- physical barrier Functions of epithelia in innate immunty

- chemical barrier (production of antimicrobial peptides) - physical barrier Functions of epithelia in innate immunty

- intraepithelial lymphocytes - normal bacterial flora - chemical barrier (production of antimicrobial peptides) - physical barrier Functions of epithelia in innate immunty

Cells of innate immunity NK cells Dendritic cells Mast cells Neutrophils Monocytes/Macrophages Phagocytosis, inflammation Phagocytosis, inflammation, T-cell activation, tissue repair Killing of infected or tumor cells Eosinophils Inflammation Defense against parasites Phagocytosis, activation of naive T-cells Cell type Pricipal function(s)

Role of phagocytes in innate immunity Order of events in infection 1. Entry of pathogen

Role of phagocytes in innate immunity Order of events in infection 1. Entry of pathogen 2. Recognition of pathogen (macrophages and dendritic cells) - molecular patterns and receptors

Molecular patterns Structures common for certain groups/classes of pathogens - essential for their life, replication and/or infectivity structures of bacterial cell wall (LPS, peptidoglycan, flagellin...) nucleic acids of pathogens (dsRNA, unmethylated CpG dinucleotides...) - not present on human cells Lipoproteins Flagellin Examples:

Role of phagocytes in innate immunity Order of events in infection 1. Entry of pathogen 2. Recognition of pathogen 3. Phagocytosis and killing of a pathogen (macrophages) - reactive oxygen species (ROS), nitric oxide (NO) and lysosomal enzymes

Phagocytosis and killing of microbes Pathogen recognition

Zipping of membrane around microbe Phagocytosis and killing of microbes

Ingestion of microbe Phagocytosis and killing of microbes

Fusion of phagosome with lysosome Phagocytosis and killing of microbes

Phagocyte activation Phagocytosis and killing of microbes

Killing of microbe Phagocytosis and killing of microbes hill.com/sites/ /student_view0/chapt er31/animation_quiz_3.html

Role of phagocytes in innate immunity Order of events in infection 1. Entry of pathogen 2. Recognition of pathogen 3. Phagocytosis and killing of a pathogen 4. Induction of inflammation (macrophages) - production of pro-inflammatory cytokines (TNF, IL-1, chemokines...)

Inflammation induction Proinflammatory cytokines TNF ― Tumor Necrosis Factor IL-1 ― Interleukin-1 Chemokines ― Chemotactic cytokines

Role of phagocytes in innate immunity Order of events in infection 1. Entry of pathogen 2. Recognition of pathogen 3. Phagocytosis and killing of a pathogen 4. Inflammation induction 5. Attraction of cells to infection site - adhesive molecules (selectins and integrins) and chemokines

Leukocytes arrive at the site of infection (extravasation) Weak binding and rolling Activation and firm binding Endothelium TNF & IL-1 Transmigration Arrival to the site of infection Selectins Integrins Various adhesive molecules Chemokines Macrophages In some inflammatory diseases therapy is directed against proinflammatory cytokines or adhesive molecules (eg: TNF in rheumatoid arthritis or VLA-4 in multiple sclerosis)

Role of phagocytes in innate immunity Order of events in infection 1. Entry of pathogen 2. Recognition of pathogen 3. Phagocytosis and killing of a pathogen 4. Inflammation induction 5. Attraction of cells to infection site 6. Pathogen elimination and/or adaptive immunity activation (dendritic cells) - cytokines, costimulatory molecules...

Role of phagocytes in innate immunity Order of events in infection 1. Entry of pathogen 2. Recognition of pathogen 3. Phagocytosis and killing of a pathogen 4. Inflammation induction 5. Attraction of cells to infection site 6. Pathogen elimination and/or adaptive immunity activation 7. Tissue repair and remodeling (macrophages) - enzymes and cytokines (growth factors, metaloproteinases...)

Role of NK cells in innate immunity Killing of cells infected by intracellular pathogens (eg. viruses) and tumor cells NK – Natural killer

Role of NK cells in innate immunity NK – Natural killer Killing of cells infected by intracellular pathogens (eg. viruses) and tumor cells Activation of macrophages (by IFN- γ )

NK cell killer function Depends on balanse of signals by activating and inhibitory receptors Inhibitory Activating

Inhibitory Activating NK cell is inhibited NO KILLING NK cell killer function Depends on balanse of signals by activating and inhibitory receptors

Inhibitory Activating NK cell is activated KILLING NK cell killer function Depends on balanse of signals by activating and inhibitory receptors

Inhibitory Activating - activating receptors recognize stress-derrived structures on cells (including infected and malignant cells) - inhibitory receptors recognize MHC class one molecule NK cell killer function Depends on balanse of signals by activating and inhibitory receptors

Mechanism of NK cell recognition

Apoptosis induction in infected and tumor cells Killing mechanisms same as in cytotoxic T-cells - Perforin and granzymes - FasL and Fas granzymes Infected or tumor cell apoptosis NK cell perforin FasL Fas NK cell killer function

- complement proteins (8 th week seminar) - other plasma proteins (CRP, MBL etc.) - cytokines Humoral mechanism of innate immunity

Cytokines in innate immunity Inflammation induction (TNF, IL-1, chemokines...)

Macrophage and NK cell Activation (IL-12 and IFN-γ) Antiviral effects (IFN type I, IFN-α and IFN-β) Differentiation of T-cell subpopulation (eg. IL-12) (eg. INF-α in HCV therapy) Cytokines in innate immunity Inflammation induction (TNF, IL-1, chemokines...)

Role of innate immunity in stimulation of adaptive immune response T or B-cells need two signals for activation First signal antigen recognition Second signal derrived by innate immunity

Thanks for your attention! Questions?

Peptide antibiotics productionj.Innate immunity cells stimulate adaptive immunity by 10. Leukocyte migrationi.Bacteria can avoid phagocytosis by9. When a target cell does not express MHC class I h.IL-12 produced by macrophages stimulates 8. Structures that a group of pathogens has in common g.Chemokynes are important for7. NK and T- cellsf.NK cells are activated6. molecules that provide “second signal”e.NK cells5. TNF, IL-1 and other mediatorsd.Macrophages kill phagocytosed microbes by 4. Polysaccharide capsule productionc.Macrophages stimmulate inflammation by production of 3. Kill our own virus-infected cellsb.Epithelial cells provide chemical barrier for pathogens by 2. Production of enzymes, ROS and NOa.Receptors on innate immunity cells recognize ____9.____8.____7.____6.____5.____4.____3.____2.____1.____ gjda bhifce