Innate cellular immunity

Transcription

1 Innate cellular immunity Bartosz Wojciuk Immunology course for the 2nd year Medical Faculty students Pomeranian Medical University Academic year 2017/2018, winter semester

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

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

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

5 Cells of the Immune System basic scheme

6 Antigen recognition Immune response Effectory mechanisms

7 Innate cellular immunity mechanisms

8 Innate cellular immunity mechanisms Inflammatory reaction NK cells function

9 Inflammatory reaction Tissue reaction that delivers mediators of host defence- cells and proteins-to sites of infection and tissue damage. Consists of recruitment of cells and leakage of plasma proteins through blood vessels and vascular tissues. Abbas, Lichtman, Pillai Basic immunology 5th Ed Elservier 2016

10 Inflammatory reaction Source: Abbas, Lichtman, Pillai Basic immunology 5th Ed Elservier 2016

11 Inflammatory reaction Breaking the skin or other epidermal layer triggers nonspecific inflammatory response in the region of the puncture Tissue damage leads to cascade of chemical signals: Release of histamine, stored in granules of mast cells into the surrounding tissue Diffusion of histamine cause that nearby capillaries become dilated and leaky, allowing passage of macrophages and increased blood flow Increased local blood supply leads to redness (cappilaries dilate and become leaky), heat and swelling (plasma leaks into the tissue) (inflammation) In damaged or infected tissue activated proteins called complement proteins and other chemicals attract phagocytes to the area Macrophages move out into damaged tissues, in interstitial spaces between cell engulfing and digesting dead cells and bacteria.

12 Inflammatory reaction

13 Antigen recognition Immune response Effectory mechanisms

14 Inflammatory reaction- initiation Pattern recognition receptors Source: Abbas, Lichtman, Pillai Basic immunology 5th Ed Elservier 2016

15 Inflammatory reaction- initiation- Pattern recognition receptors Source: Abbas, Lichtman, Pillai Basic immunology 5th Ed Elservier 2016

16 Antigen recognition Immune response Effectory mechanisms

17 Phagocytosis Phagocytosis = process of engulfment and destruction of extracellularly - derived materials by phagocytic cells Phagocytic cells (phagocytes): monocytes, macrophages and polymorphonuclear leucocytes (PMNs)- neutrophils. professional phagocyte or eating cell (phago= eating, cyte= cell).

18 Phagocytosis Phagocytosis involves the ingestion and digestion of: - microorganisms - insoluble particles - damaged or dead host cells - cell debris - activated clotting factors

19 Phagocytes - Neutrophils (PMNs) Characteristic nucleus (lobed), Granules CD 66 membrane marker Function: are recruited to the site of infection where they kill invading organisms intracellularly and then die contribute to collateral tissue damage that occurs during inflammation

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

21 Phagocytes Monocytes, Macrophages Characteristic nucleus (kidney-shaped) Not granules, but have numerous lysosomes CD14 membrane marker Different cells: Monocytes- in blood Tissue macrophages: in the lungs - pulmonary macrophages, in the liver - Kuppfer cells; histiocytes in connective tissue

22 The functions of macrophages phagocytosis and intracellular killing of microorganisms extracellular killing of infected or altered self target cells contribute to tissue repair act as antigen-presenting cells (APC), which are required for the induction of specific immuno response.

23 Macrophages differentiation Source: Male, Brostoff, Roth, Roitt Immunology Ed 8th Elservier Saunders 2013

24 QUIZ?!

25 The stages of phagocytosis Chemotaxis Vascular adherence Diapedesis Engulfment (by endocytosis) Phagocytosis/ intracellular killing

26 The stages of phagocytosis: Chemotaxis Residual macrophages and mastocytes recognize pathogen associated molecular patterns (PAMPS) and pattern recognition receptors (PRR) Circulating PMNs and monocytes respond to danger (SOS) signals (peptides released by bacteria, clotting system peptides, C products and cytokines) generated at the infection site- using pathogen associated molecular patterns (PAMPS) and pattern recognostion receptors (PRR) like Phagocytes recognize chemicals (i.e. SOS signals) produced by bacteria and migrate toward the smell - movement towards a an increasing chemical gradient of chemotactic agents. The chemotactic agents: C3a, C5a, LPS, peptidoglycan, teichoic acids, fibrinogen, PAF, LTB4, Il-1. Il-8, eosinophil chemotactic factor, or neutrophil chemotactic factor Some of the SOS signals in tissue spaces attract phagocytes to the infection site by chemotaxis and activate them (increase phagocytosis and intacellular killing of the invading organisms).

27 The stages of phagocytosis: Vascular adherence Some of the SOS signals stimulate endothelial cells (near the infection site) to express cell adhesins such as ICAM-1 and selectines.they bind to components on the surface of phagocytes and cause adhesion of the phagocytes to endothelium works reasonably well for whole bacteria or viruses, but less so for proteins or encapsulated bacteria. In order to deal more effectively with encapsulated bacteria, antibodies directed against the capsule enable the phagocytic cells to ingest the organisms, using their Fc receptors.

28 The stages of phagocytosis Diapedesis Vasodilators produced at the infection site loose the junctions between endothelial cells and then the phagocytes pass through the endothelial barrier by squeezing between the endothelial cells in a process called diapededsis.

29 Initiation of Phagocytosis Phagocytic cells have a variety of receptors on their cell membranes: Fc receptors (FcR) Binding to the Fc receptor requires prior interaction of the antibody with an antigen, binding of IgG-coated bacteria enhanced phagocytosis and activation of the metabolic activity of phagocytes (respiratory burst) Complement receptors (C3bR) for the C3b -enhanced phagocytosis and stimulate respiratory burst. Scavenger receptors bind a wide variety of polyanions on bacterial cells Toll-like receptors (TLR) = (Pattern Recognition Receptors (PRRs) recognize broad molecular patterns called PAMPs (pathogen associated molecular patterns) on infectious agents Binding results in phagocytosis and the release of inflammatory cytokines (IL-1, TNF-alpha and IL-6) by the phagocytes

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

31 Opsonin An opsonin (Greek word meaning prepare for eating ) is a plasma protein that will attach to a foreign substance and prepare it for phagocytosis. Types of opsonins include:c-reactive protein (CRP), complement (C3b), antibodies (IgM and IgG)

32 Bacteria in extracellular space Effector mechanisms against extracellular pathogens OPSONISATION + Ab OPSONISATION Fc receptor binding Phagocytosis

33 Bacteria in plasma + Ab & COMPLEMENT Effector mechanisms against extracellular pathogens COMPLEMENT Activation Lysis Opsonisation Complement & Fc receptor binding Phagocytosis

34 The stages of phagocytosis- scheme: 1. Attachment of the bacterium to the long membrane evaginations called pseudopodia. 2. Phagosome formation - ingestion of the bacterium forming a phagosome, which moves toward the lysosome. 3. Phagolysosome formation- fusion of the lysosome and phagosome, releasing lysosomal enzymes into the phagosome and intracellular killing oxygen- dependent and oxygen-independent pathways are activited (respiratory burst). 4. Intracellular killing/digestion of the ingested material 5. Release of digested products from the cell.

35 Intracellular killing is known as the oxidative burst, and leads to digestion of the phagolysosomal contents, after which they are eliminated by exocytosis.

36 Killing by phagocytes is made possible by : phago-lysosome,which contains next substances: - hydrogen peroxide (H2O2) - oxygen free radicals - peroxidase, - lysozyme - hydrolytic enzymes

37 Intracellular killing invloves the following mechanisms: oxygen-dependent The consequence of the respiratory burst is the greater number of oxygen-containing compounds myeloperoxidase-independent myeloperoxidase-dependent oxygen-independent bacteria can be killed by pre-formed substances released from granules or lysosomes Nitric oxide-dependent killing (only macrophages)

38 Intracellular Killing Pathways Intracellular Killing Oxygen Dependent Oxygen Independent Myleoperoxidase Dependent Myleoperoxidase Independent

39 Respiratory Burst Oxygen-Dependent Myeloperoxidase-Independent Reactions During phagocytosis glucose is metabolized via the pentose monophosphate shunt and NADPH is formed. Cytochrom B which was part of the specific granule combines with the plasma membrane NADPH oxidase and activates it. The activated NADPH oxidase uses oxygen to oxidize the NADPH. The result is the production of superoxide anion(o 2- ). Some of the superoxide anion is converted to H 2 O 2 and singlet oxygen by superoxide dismutase. Superoxide anion can react with H 2 O 2 resulting in the formation of hydroxyl radical and more singlet oxygen. The result of all these reactions is the production of the toxic oxygen compounds superoxide anion (O 2- ), H 2 0 2, singlet oxygen ( 1 O 2 ) and hydroxyl radical (OH)

40 Respiratory Burst Oxygen-Dependent Myeloperoxidase-Independent Reactions Glucose +NADP + NADPH + O 2 G-6-P-dehydrogenase NADPH oxidase Cytochrome b558 Pentose-P + NADPH NADP + + O 2-2O H + Superoxide dismutase H2 O O 2 2O H2 O 2 OH* + OH O 2 Toxic compounds Superoxide anion (O 2 - ), Hydrogen peroxide (H 2 O 2 ), Singlet oxygen ( 1 O 2 ) and Hydroxyl radical (OH*)

41 Oxygen-Dependent Myeloperoxidase-Dependent Reactions As the azurophilic granules fuse with the phagosome, myeloperoxidase is released into the phagolysosome. Myeloperoxidase utilizes H 2 O 2 and halide ions (usually Cl - ) to produce hypochlorite, a highly toxic substance. Some of the hypochlorite can spontaneously break down to yield singlet oxygen. The result of these reactions is the production of toxic hypochlorite (OCl - ) and singlet oxygen ( ).

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

43 Respiratory Burst Detoxification Reactions of Oxygen Dependent pathway PMNs and macrophages have means to protect themselves from the toxic oxygen intermediates. These reactions involve the dismutation of superoxide anion to hydrogen peroxide by superoxide dismutase and conversion of hydrogen peroxide to water by catalase

44 Respiratory Burst Detoxification Reactions of Oxygen Dependent pathway 2O H + 2 H 2 O 2 Superoxide dismutase Catalase H 2 O 2 + O 2 H 2 O + O 2

45 Nitric oxide-dependent killing Binding bacteria to macrophages, particularly binding via Toll-like receptors results in the production of TNF-alpha, which induce the expression of the inducible nitric oxide synthetase gene resulting in the production of nitric oxide (NO). If the cells also exposed to interferon gamma additional nitric oxides will be produced. Nitric oxide released by the cell is toxic and can kill microorganism in the vicinity of the macrophage.

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

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48 Innate cellular immunity mechanisms Inflammatory reaction NK cells function

49 Natural killer ( NK ) cells NK APPEARENCE also known as large granular lymphocytes (LGL) are lymphocytes - neither T cells nor B cells are slightly larger have numerous granules NK IDENTIFICATION by: the presence of CD56 and CD16 (Fc-γR III) receptors a lack of CD3 cell surface markers. NK PRODUCTION are still produced and present in organism Blood % of lymphocytes Liver-50%; spleen-10%; lymph nodes-2-7%

50 NK cells - missing self theory : NK FUNCTION dosen t show immunologic memory are not antigen specific are specialized to kill certain types of target cells: virus infected host cells malignant (host) cells graft cells Above mentioned modified host cells loose the host antigens (ex. MHC class I molecule) and then became the target for the NK cells

51 Why do NK cells kill some host cells? Normal cells constitutively express MHC class I molecules on their surface, however, virus infected and malignant cells down regulate expression of MHC-I molecule. Thus NK cells selectively kill virus-infected and malignant cells sparring normal cells. Viruses often suppress MHC expression in infected cells Cancer cells have reduced or no class I MHC expression, Graft cells have another MHC I

52 INHIBITION of NK Healthy host cell: Inhibition KIL(MHC-I) + Activation KAL(stress-induced proteins) + NK cell KIR KAR ACT + INHIB INHIB (no killing) The effector function of NK is trigerred by a balance between opposite signals. If both inhibitory and activating signal is detected the NK cell will not be stimulated to kill

53 ACTIVATION of NK Virus infected host cell: Inhibition KIL (MHC-I) + Activation KAL + NK cell KIR KAR ACT alone granule release cell death (killing) Upon positive stimulus (i.e. stress- induced proteins, lack or reduced MHC-I molecules) an NK cell will kill. An inhibitory signal MUST be present to turn off the NK cell

54 NK cytotoxity Exocytosis of cytotoxic granule contents with: perforin - pore-forming proteins granzymes - enzymes that activate a group of protease enzymes called caspases and lead to apoptosis of the infected cell by means of destruction of its structural cytoskeleton proteins and by chromosomal degradation. NKCF Receptor interactions Fas protein (target cell) - FasL (NK cell)- leads to apoptosis

55 Other funtions: of NK cells NK cells secrete cytokines such as the: - anti-viral cytokine IFN- gamma - inflammatory cytokine TNF-alfa Il-2, Il-3, Il-5, Il-8 take part in ADCC- antibody dependent cell cytotoxity- K cells. Binding of NK cell to antibodycoated target cells also initiates killing, but this is not controlled by an inhibitory signals.

56 NK cells LAK cells NK ACTIVATION don t have to be acivated But activation increase their activity - activated mainly by: IL-2 and IFN-gamma to become LAK cells (lymphokine activated cells) (also Il-12,15,18), - continued exposure to Il-2 and INFγ (gamma) enables the LAK cells to kill transformed as well as malignant cells. - LAK cell therapy is one approach for treatment of malignancies - LAK cells are inhibited by: PGE2 (prostaglandin 2), cortisole

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

58 K Cells (ADCC) morphologically similar to NK cell have Fc receptor (CD 16) recognize Fc part of antibody (IgG) coated target cell except K cell in ADCC reaction participate macrophages

59 Antibody-dependent cell cytotoxicity ( ADCC ) - The Fab fragment of the antibody binds to epitopes on the foreign/target cell. - The NK cell then - binds to the Fc fragment of the antibody, because has (FcγR = CD16) receptor, which recognize this fragment of antibody. - Release perforines and granzymes from cytotoxic granules

60 Other functions of NK cells Interaction of NK cells and macrophages Source: Abbas, Lichtman, Pillai Basic immunology 5th Ed Elservier 2016

61 Laboratory methods for studying of phagocytosis process 1) Chemotaxis agar plate assay two-chamber assay according to Boyden 2) Engulfment process phagocytosis assay 3) Activty of oxygen-dependent killing system spontanous nitroblue tetrazolium test = (NBT test) induced nitroblue tetrazolium test = (NBT test)

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63 Phagocytosis

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