31. Cell Death and Repair, Inflammation, Anti-Inflammatories Flashcards

Question

What is abundance of leukocytes in the blood (in cells/L)?

Answer 1

7 x 10⁹ cells/L

Answer 2

* Neutrophils -\> 40-70% * Lymphocytes -\> 20-40% * Monocytes -\> 6% * Eosinophils -\> 3% * Basophils -\> 1%

Answer 3

* Bacterial infections * Stress

Answer 4

* Neutrophils: * Bacterial infections * Stress * Lymphocytes: * Mononucleosis * Whooping cough * Viral infections * Monocytes: * Malaria * TB * Fungal infections * Eosinophils: * Allergic reactions * Autoimmune diseases * Parasitic worms * Basophils: * Cancers * Chicken pox * Hypothyroidism

Answer 5

* A type of immune cell that has granules (small particles) with enzymes that are released during infections, allergic reactions, and asthma. * Neutrophils, eosinophils, and basophils are PMNs. * For some reason, the spec calls neutrophils PMNs (almost implying that eosinophils and basophils are not, so double check this!)

Answer 6

In the bone marrow.

Answer 7

* GM-CSF * G-CSF These colony stimulating factors are glycoproteins. GM-CSF is a cytokine that acts as growth factor, stimulating the production of granulocytes and monocytes in the bone marrow, with G-CSF specifically increasing neutrophil numbers

Answer 8

Bone marrow (50% of the nucleated leukocytes in bone marrow are PMNs)

Answer 9

* In response to infection * This is called granulocytosis/neutrophilia

Answer 10

Neutropenia, caused by: * X-irradiation * Chemotherapy * Kostmann disease These patients are susceptible to bacterial and fungal infection.

Answer 11

Increased/Decreased granulocytes in the blood, although typically this may be used to simply refer to neutrophilc counts, since they are the most abundant.

Answer 12

They are mobilised to sites of infection.

Answer 13

Yes, so they do not synthesis DNA, although they do synthesis some limited mRNA and proteins.

Answer 14

They undergo apoptosis and are cleared by tissue macrophages.

Answer 15

Hematopoietic stem cell -\> Myeloid stem cell -\> Myeloblast -\> Granulocytes

Answer 16

It is also known as severe congenital neutropenia: * A group of rare disorders that affect myelopoiesis, causing a congenital form of neutropenia. * SCN manifests in infancy with life-threatening bacterial infections. * Most cases of SCN respond to treatment with granulocyte colony-stimulating factor, which increases the neutrophil count and decreases the severity and frequency of infections.

Answer 17

Serum proteins that attach to the surface of microbes, rendering them more attractive to phagocytes.

Answer 18

* IgG -\> Binds to Fc receptor [IMPORTANT] * C3b (complement) -\> Binds to CR3 receptor [IMPORTANT] * Surfactant proteins A and D -\> ??? * C-reactive protein (CRP) -\> ???

Answer 19

Neutrophils and macrophages (Mast cells and dendritic cells also phagocytose, to a lesser extent)

Answer 20

* PAMPs * DAMPs * Opsonins In essence, you can think of the phagocyte as being able to recognise conserved molecules (**PAMPs and** **DAMPs**) via the **PRRs** it has on its surface. However, the phagocyte can also recognise **opsonins** using **opsonin receptors**,

Answer 21

* Phagocytosis is triggered by: * PAMPs and DAMPs binding to PRRs on the phagocyte surface * Opsonins (like IgG) binding to opsonin receptors (on the phagocyte) * A suggested mechanism for engulfing the pathogen is the zipper mechanism, where the binding points are used to gradually move the cytoplasm around the pathogen * Engulding occurs via pseudopods that move around the bacterium to create a phagosome. This process is dependent on actin remodelling. * The phagosome then fuses with a lysosome and granules, which enables digestion of the bacterium by a variety of mechanisms.

Answer 22

* Pseudopods around the bacterium to create a phagosome. * This process is dependent on actin remodelling, which can be experimentally demonstrated by cytochalasins. * These are fungus-derived products that block actin polymerisation, so that formation of a phagosome is inhibited.

Answer 23

* Regurgitation while feeding -\> Can damage local cells * Frustrated phagocytosis (exocytosis) -\> Release of toxic agents into the environment when the phagocyte fails to engulf its target * Surface phagocytosis * Bacteria evasion of phagocytosis

Answer 24

If a phagocyte fails to engulf its target, toxic agents can be released into the environment.

Answer 25

* The phagosome fuses with a lysosome * It is also further acidified by activation of a V-ATPase on the surface * This eventually leads to digestion and destruction of the pathogen inside

Answer 26

* Oxygen-dependent antibacterial mechanisms -\> Using oxidising radicals and halides to kill the pathogen * Oxygen-independent antibacterial mechanisms -\> Using enzymatic and non-enzymatic mechanisms to kill the pathogen

Answer 27

Respiratory burst

Answer 28

* Following uptake of pathogens for phagocytosis, the oxygen demand of phagocytes increases. * The oxygen burst is used largely to generate NADPH from glucose via the pentose phosphate pathway. The NADPH in turn can be used to generate reactive species that kill pathogens.

Answer 29

* Upon uptake of a pathogen, oxygen is used to rapidly generate NADPH from glucose via the pentose phosphate pathway. * The NADPH in turn can be used to generate superoxide (O₂^-), which then forms hydrogen peroxide (H₂O₂) via breakdown. These are then used in the production of reactive oxygen species (ROS): * Superoxide and hydrogen peroxide can react with each other to produce hydroxyl radicals * In neutrophils, hydrogen peroxide can react with halide ions to oxidise them, which is catalysed by MPO (myeloperoxidase) in the phagolysosome. * The NADPH is also used in the generation of nitric oxide (NO) (see other flashcard).

Answer 30

* The importance of oxygen-dependent killing mechanisms can be demonstrated by culturing bacteria with neutrophils, both in the presence and absence of oxygen. * Faster culture growth is seen in the deoxygenated experiment.

Answer 31

MPO (myeloperoxidase)

Answer 32

They are powerful oxidising agents, and lipid oxidation is particularly effective for breaking down cell membranes.

Answer 33

* Individuals have a defect in the phagocyte NADPH oxidase enzyme that catalyses the reaction of NADPH with O₂ to produce superoxide. * The symptoms include a higher susceptibility to and frequency of infection, as well as the development of granulomas (collections of macrophages) in various tissues, both of which are due to the reduced immune capacity of phagocytes. * Treatment involves antibiotic use to manage infection, and cure is currently only possible via use of hematopoietic stem cell transplant.

Answer 34

* Proteases * Phospholipases * Nucleases * Lysozyme * Cationic proteins (BPI & ECP) * Lactoferrin * Defensins (Anti Microbial Peptides – AMPs)

Answer 35

Lysozyme breaks down the peptidoglycan in the cell wall of bacteria.

Answer 36

Modify cell membranes, such as BPI (bactericidal/permeability-increasing protein) which acts on lipopolysaccharides.

Answer 37

Lactoferrin reduces the amount of iron available for bacterial use, which is significant because iron is an essential ion for bacterial growth. It can also bind to LPS and thus lead to cell lysis.

Answer 38

* Peptides (AMPs) of fewer than 50 amino acids that are an evolutionarily conserved part of the innate immune response * Primarily target the cell membrane and create transmembrane channels, meaning that they have broad specificity within bacteria and other pathogens. * They are not affected by antibiotic resistance of a bacterium. * Experimentally, the broad specificity of AMPs can be demonstrated by an *in vitro* assay.

Answer 39

LL-37 and defensins

Answer 40

* NADPH (from the respiratory burst) here is also used in the generation of nitric oxide (NO), which is a substrate (along with superoxide), for the production of more reactive nitrogen species. * Nitric oxide synthase 2 is inducible mostly in macrophages (by inflammatory mediators). * Reactive nitrogen species have broad antimicrobial action by reacting with transition-metals in proteins (e.g. haemoglobin or cytochrome c) or the amino acids in a protein.

Answer 41

* Neutrophil extracellular traps * Neutrophils have a short lifespan (relative to macrophages), but before and during apoptosis they leave an extracellular net of DNA and histones, with proteins such as MPO bound to them. * These bound proteins have antimicrobial properties, so the net functions to kill pathogens outside of cells.

Answer 42

(Zychlinsky, 2009): * These may include prevention of formation of the NET by catalase and digestion of the NET by endonuclease, along with some protection provided by the bacterial capsule * Studies of this rely partly on observation of NET formation in vitro and comparisons between the resistance of known bacteria to neutrophils and NET.

Answer 43

* Rapid (10-120mins) -\> Faster than apoptosis * Active against a wide range of pathogens * Trap bacteria locally to prevent spread * Work even when the neutrophil is dead

Answer 44

* ROS (reactive oxygen species) * Degranulation (especially elastase) * Activate cascades (e.g. caogulation and complement) Conditions involving tissue damage relating to neutrophil activation include: emphysema, septic shock and ARDS.

Answer 45

Note that macrophages are derived from blood monocytes.

Answer 46

* Phagocytosis * Degranulation (of anti-microbial agents) * Production of NETs * Mediation of inflammation (via release of cytokines)

Answer 47

Defence: * Phagocytosis and killing * Control of inflammation -\> Via cytokines and interferons * Antigen presentation Tissue maintenance: * Tissue homeostasis via scavenger receptors * Tissue remodelling * Apoptotic cell clearance * Tissue repair (e.g. in wound repair)

Answer 48

* They have overlapping function, in terms of phagocytosis and release of cytokines. * However, neutrophils can also degranulate anti-microbial substances and release NETs, while macrophages can also perform tissue maintenance and antigen-presentation. * Neutrophils are rapidly recruited, but are short-lived and act via enzymatic responses that are short-lasting, making them more numerous in acute inflammation. * Macrophages are slowly recruited (they are initially monocytes in the blood) and act via changes in gene transcription that have more lasting effects, so they play a larger role in chronic inflammation.

Answer 49

No, some tissue resident macrophages are derived from myeloid precursors in embryonic life and proliferate in situ throughout adult life.

Answer 50

* Embryonic yolk sac derived tissue macrophages (long-lived, self-renewing) * Macrophages that are formed by bone marrow-derived monocytes that infiltrate the tissue

Answer 51

* Tissue resident (e.g. Kupffer cells) macrophages (mostly arising from embryonic yolk sac) -\> Mediate homeostasis, repair and remodelling * Infiltrating monocytes that become inflammatory macrophages -\> Antimicrobial functions

Answer 52

* Macrophage gene expression is very plastic and hence so is their phenotype * We know that a wide range of cytokines act on monocytes to give multiple macrophage types M0, M1, M2 in our in vitro experimental systems * In vivo we now appreciate that monocytes can differentiate into many different cell types including myeloid-derived dendritic cells (mDCs), Tumour Associated Macrophages (TAMs) and myeloid derived suppressor cells (MDSCs)

Answer 53

* Macrophages can differentiate during development to give various types of resident macrophages * They can also respond to environmental signals, including cytokines, transcription factors and epigenetic changes Note that the diagram shows the resident tissue macrophages as being derived from bone marrow (presumably via monocytes). This used to be the dominant theory, although we now know that most come from embryonic yolk sac, so I'm not sure why this is drawn this way.

Answer 54

A process by which macrophages adopt different functional programs in response to the signals from their microenvironment: * M1 macrophages -\> Promoted by IFN-γ and have a more classical pro-inflammatory and pro-immune role * M2 macrophages -\> Promoted by IL-4 and IL-13, and have a more anti-inflammatory role and suppress immunity

Answer 55

* A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances which it is unable to eliminate. * Langhans giant cell -\> An accumulation of several macrophages, containing a ring of macrophage nuclei * Epitheliod macrophages -\> Look like epithelial and have a busy nucleus to secrete huge amounts of proteins

Answer 56

Pattern-recognition receptors (PRRs)

Answer 57

* Pattern-recognition receptors * These are receptors on the surface of cells of the innate immune response * They bind PAMPs and DAMPs

Answer 58

They bind to ligands that are not variable and are present during a pathogenic infection (PAMPs and DAMPs), so they allow us to differentiate between a pathogen and a non-harmful foreign substance (e.g. a salmon sandwich).

Answer 59

Mainly cells of the innate immune system, such as dendritic cells, macrophages, monocytes, neutrophils and epithelial cells.

Answer 60

* Pathogen-associated molecular patterns * These are molecules that are highly conserved between pathogens, so that their detection by PRRs tells the immune cell that this is a pathogen * An example is LPS

Answer 61

* Damage-associated molecular patterns * These are typically nuclear or cytosolic proteins with defined intracellular function that, when released outside the cell after tissue injury, denature and activate PRRs. * They essentially signal to immune cells that host cell damage has occurred and therefore trigger an inflammatory response. * An example is DNA.

Answer 62

* Innate immunity * Acquired immunity * Auto-immunity

Answer 63

They are expressed mostly in innate immune cells: * Cytosolic PRRs * Cell-surface PRRs -\> On both neutrophils and macrophages, but more types on macrophages Some are also secreted into the plasma: * Certain acute phase reactants (floating free in the plasma) -\> These tend to activate complement, which in turn activates phagocytes

Answer 64

* Mannose-binding lectin (MBL) * C-reactive protein (CRP) Both of these are involved in complement, meaning that they trigger phagocytes indirectly.

Answer 65

* NLRs (Nod-like receptors): * NODs [IMPORTANT] * NLRPs * RIG

Answer 66

* TLRs (Toll-like receptors) [IMPORTANT] * Macrophage scavenger receptor * Lectins: * Dectin-1 (in macrophages and neutrophils) * Macrophage mannose receptor

Answer 67

Neutrophils and macrophages both have PRRs, but macrophages have more cell-surface PRRs, including mannose receptors and scavenger receptors.

Answer 68

* Opsonic * **Phagocytic receptors** -\> These bind to opsonins (such as IgG and complement components) that are marking out pathogens for phagocytosis (e.g. Fc receptors and CR3) * Non-opsonic: * PRRs * **Phagocytic receptors** -\> These bind to PAMPs/DAMPs and trigger phagocytosis (e.g. lectins and macrophage scavenger receptor, mostly in macrophages) * **Non-phagocytic** -\> These bind to PAMPs/DAMPs and assist with phagocytosis, but do not trigger it (e.g. TLRs). They also lead to release of cytokines (e.g. NLRs). * **Cytokine receptors** -\> Involved in cytokine release and killing mechanisms (not phagocytosis) * **GPCRs** -\> Mostly involved in recruitment of the phagocyte Don't deep the whole phagocytic/non-phagocytic thing. Just remember that TLRs and NLRs are not phagocytic like you might expect. Thus, in the diagram, phagocytic receptors refer to opsonic receptors and PRRs apart from TLRs and NLRs.

Answer 69

* TLRs * NLRs (such as NOD) TLRs may stimulate, but do not trigger phagocytosis, while NOD receptors lead to the release of cytokines.

Answer 70

They are receptors on phagocytes that bind to opsonins that are marking out cells for phagocytosis: * Fc receptors (on neutrophils and macrophages) -\> Bind to the Fc region of IgE immunoglobulins * CR3 -\> Binds to iC3b, which is part of the complement cascade

Answer 71

Macrophages

Answer 72

* They are a type of PRR found on macrophages * They trigger phagocytosis * They bind to non-native LDL, and features of bacteria (e.g. LPS)

Answer 73

* (Brown, 1983) found that scavenger receptors lead to the uptake of modified LDL by macrophages to give foam cells. * Clinically, this is relevant in the development of atherosclerosis (and possible subsequent myocardial infarction or stroke), since macrophages that are recruited to fatty deposits in arteries can convert ingested LDL to cholesterol and become foam cells that form the plaque. Depending on conditions, the foam cells can then promote further foam cell formation.

Answer 74

* They are carbohydrate-binding proteins that are highly specific for sugar groups of other molecules * They act as phagocytic receptors * They include, for example, dectin-1 and macrophage mannose receptor

Answer 75

* Dectin-1 * Found on macrophages and neutrophils * Binds to fungal polysaccharides * Stimulates phagocytosis and release of TNF-α * Macrophage mannose receptors * Found on macrophages * Bind to mannose and fucose at the ends of glycoproteins and glycolipids, which are predominantly found in bacterial cells * Stimulates phagocytosis

Answer 76

Dectin-1 knockout mice are more susceptible to fungal infection.

Answer 77

Toll-like receptor

Answer 78

* The Drosophila Toll gene is required for dorso-ventral axis formation in fly embryos. * Toll is also important for the Drosophila response to fungal but not bacterial pathogens. * Unlike Drosophila Toll, the 10 mammalian TLRs have no role in development.

Answer 79

* They are a type of PRR that is non-opsonic and non-phagocytic. * Activation leads to amplification and changes to transcription that are pro-inflammatory. * This leads to inflammatory cytokine production, proliferation and sometimes greater adaptive immunity.

Answer 80

* Macrophages express at least TLR2, TLR4 and TLR9. * Neutrophils only express TLR2 and TLR4, in very small amounts.

Answer 81

* TLR2:TLR6 dimer -\> Recognises teichoic acids * TLR4 -\> Recognises LPS * TLR5 -\> Recognises flagellin * TLR3, TLR7, TLR8, TLR9 -\> Recognise genetic material inside cells (Note: Not all of these are expressed by macrophages and neutrophils. In an essay, it is best to be clear about this.)

Answer 82

* LBP transfers LPS to the immune cell (macrophage) CD14 receptor * CD14 facilitates TLR4 recognition of LPS * This requires MD-2 (bound to TLR4) * Inside the cell, TLR4 binds MyD88, which sets of a phosphorylation cascade * This ultimately results in NF-κB entry into the nucleus, stimulating transcription of cytokines

Answer 83

TLR signalling

Answer 84

* TNF-α * Activates vascular endothelium, increasing cell and metabolite entry * Fever * IL-1β * Activates vascular endothelium and recruitment of lymphocytes, increasing cell and metabolite entry * Fever, along with IL-6. * IL-6 * Fever * IL-12 (in chronic inflammation) * Actives macrophages (via IFN-γ production) and NK cells * CXCL8 * Recruits neutrophils and basophils

Answer 85

* IL-10 * Downregulates the expression of helper T-cell cytokines, MHC class II antigens, and co-stimulatory molecules on macrophages. * Enhances B cell survival, proliferation, and antibody production. * Inhibits pro-inflammatory cytokines TNF-α, IL-1β, IL-12 and IFNγ secretion.

Answer 86

* Opsonic receptors are critical for phagocytosis * Phagocytic PRR receptors can be considered a back-up to this

Answer 87

* NOD-like receptors * This is a family of cytosolic PRRs, including NOD1/2 and NLRPs * Found in macrophages (and maybe neutrophils?) * NOD1/2 -\> Lead to release of cytokines * NLRPs -\> Are a component of the inflammasome, a molecular assembly that regulates IL-1 and IL-18 secretion in response to intracellular bacterial toxins.

Answer 88

* When there is damaged tissue (due to infection or otherwise), the cells there detect the damage and send out cytokines * These recruit immune cells and induce a state of inflammation * Thus, the symptoms experienced are not due to the infection, but much rather the immune response itself

Answer 89

* Swelling (tumor/oedema) * Redness (rubor) * Heat (calor) * Pain (dolor) Inflammation leads to loss of function.

Answer 90

An accumulation of fluid, living and dead white blood cells, dead tissue, and bacteria or other foreign invaders or materials.

Answer 91

* A localized collection of pus in any part of the body, often caused by an infection by pyogenic bacteria. * An abscess is a circumscribed cavity filled with pus (purulent exudate) that is associated with liquefactive necrosis of related solid tissue.

Answer 92

Their interiors have little or no vascularization, making it difficult to deliver therapeutic agents effectively.

Answer 93

* Resolution with no scarring * Resolution with scarring * Rupture external * Rupture internal -\> Leading to a septic embolus * Cyst formation (neutral outcome)

Answer 94

Surgical drainage and antibiotics

Answer 95

* PAMPs are present in infection and DAMPs are released by tissue damage * Resident macrophages, mast cells and dendritic cells release chemical mediators in response * These increase the permeability of local venules * This causes cells, fluid and plasma proteins to enter the site of injury/infection

Answer 96

Resident macrophages, mast cells and dendritic cells.

Answer 97

Rapidly recruited: * Neutrophils * Platelets Recruited soon after: * Monocytes (that become macrophages) * T-lymphocytes If the site is of allergic inflammation: * Eosinophils/Basophils

Answer 98

* Albumin * Antibodies * Complement proteins * Coagulation factors

Answer 99

Albumin released as part of the exudate leads to osmotic pressure that pulls water in.

Answer 100

* Margination * Leukocyte rolling * Leukocyte activation * Leukocyte tight adhesion * Diapedesis (Leukocyte extravasation) * Chemotaxis

Answer 101

* The cells at the site of inflammation send out cytokines and other molecules to partially activate neutrophils and macrophages passing through an adjacent venule * This triggers them to cross the blood vessel barrier * Once crossed, the neutrophils and macrophages follow chemokines, pathogen molecules and other molecules to the site of infection * Here they are fully activated

Answer 102

* It is the process of leukocytes being forced to flow along the outside of venules. * This is the first step in their recruitment to sites of inflammation.

Answer 103

* Histamine -\> Vasodilation, Vascular leakage * Serotonin (5HT) * Bradykinin (BK) * Platelet Activating Factor (PAF) -\> Vasodilation * Prostanoids * Prostaglandins (e.g. PGI2 - prostacyclin) -\> Vasodilation * Thromboxanes (e.g. TxA2)

Answer 104

* Released from mast cells * Stored in granules with heparin * Acts via histamine receptors -\> H1-H4 * Actions: * Increased vascular permeability (H1) * Smooth muscle cell contraction (H1) * Vasodilatation (H1) * Cardiac stimulation (H2) * Stimulation of gastric secretion (H2)

Answer 105

"Triple reaction of Lewis" a.k.a. "Wheal and flare": * When skin is gently scratched for some time, there are 3 stages to the reaction: * Initial red line * Flare around the line * Light wheal replaces the line * This same response can be obtained by injecting histamine

Answer 106

* Released from activated inflammatory cells * Derived from phospholipids via phospholipase A2 * Acts on GPCRs * Main actions: * Vasodilatation * Aggregation of platelets * Increased vascular permeability * Leukocyte chemotaxis * Leukocyte activation * Bronchospasm

Answer 107

The rolling of leukocytes along venule walls due to weak attractions.

Answer 108

Selectins enable weak interactions between the venule wall and the leukocyte: * Endothelial cells express * P-selectin * E-selectin * L-selectin ligands * Leukocytes express * L-selectin * P-selectin ligands

Answer 109

* P-selectin -\> Released from Weibel-Palade bodies by histamine or thrombin * E-selectin -\> Transcription upregulated by TNF-α, IL-1, LPS

Answer 110

* TNF-α * Activates vascular endothelium, increasing cell and metabolite entry * Fever * IL-1 * Activates vascular endothelium and recruitment of lymphocytes, increasing cell and metabolite entry * Fever, along with IL-6. * IL-6 * Fever

Answer 111

* It occurs via GPCRs on the leukocytes * The molecules that stimulate these mostly include cytokines, C5a, PAF and others Note that partial activation occurs during recruitment of the leukocytes, while complete activation occurs at the site of inflammation.

Answer 112

* Leads to altered conformations of cell surface integrins on the leukocytes * The integrins can now form tight interactions with cell adhesion molecules on endothelial cells * Thus, the leukocytes adhese to the vessel wall

Answer 113

ICAM interactions: * Integrins on the leukocyte surface undergo a conformational change upon activation of the leukocyte * This allows the integrins to bind to cell-adhesion molecules on endothelial cells * This ICAM interaction is necessary to halt leukocyte rolling and start diapedesis (NOTE: The diagram also shows the selectin interactions involved in leukocyte rolling)

Answer 114

* The β-2 integrin subunit may be absent in patients with leukocyte adhesion deficiency (LAD) * In these cases, neutrophils and macrophages cannot access the site of inflammation * The first sign of this may be seen in babies, where there is a lack of neutrophils entering the stump of the umbilical cord

Answer 115

Classical activation: * Produces M1 macrophages, which have a pro-inflammatory and pro-immune role * Activated by IFN-γ (during recruitment) and LPS Alternative activation: * Produces M2 macrophages, which have a more anti-inflammatory role and suppress immunity * Activated by IL-4 and IL-13 (during recruitment) (Check whether the cytokines act during recruitment!)

Answer 116

Diapedesis

Answer 117

* They must cross the basement membrane * Neutrophils do this by secreting neutrophil elastase, while macrophages use collagenases * Then they must move between endothelial cells, using CD31

Answer 118

A family of small cytokines that can induce chemotaxis in nearby responsive immune cells.

Answer 119

Movement of a cell in a direction corresponding to a gradient of increasing or decreasing concentration of a particular substance.

Answer 120

* Bacterial products, namely N-formylmethionine (fMLP - an amino acid used to initiate protein synthesis in bacterial cells) -\> mFLP receptor * Cytokines and chemokines (e.g. IL-8, CCL5, etc.) -\> IL-8 receptor, CCR5, etc. * C5a (a chemoattractant product of complement) -\> C5a receptor * Platelet-activating factor (PAF) -\> PAF receptor

Answer 121

* It moves by cytoskeleton remodelling * The protrusions at the front are called pseudopods, while the tail at the back is called the uropod

Answer 122

* There is a membrane between two chambers, with small holes in it * Chemoattractant (CCL5, in this case) is placed in one chamber, while leukocytes expressing a certain type of chemokine receptor are placed in the other chamber * The graph shows that the rate of crossing of leukocytes is greatest when the leukocytes are made to express CCR5, which is the receptor for CCL5

Answer 123

* Minutes to days * It acts to recruit neutrophils to the site of infection and activates them. These neutrophils and other molecules in turn activate other leukocytes.

Answer 124

* Heat is one of the cardinal signs of acute inflammation. This effect is local and is caused mainly by vasodilatation. * Some cytokines generated at sites of inflammation can: * Act distally to cause systemic inflammation * Act at the hypothalamus to raise the set point * e.g. TNF & IL-1 * Localised mechanisms of acute inflammation if initiated throughout the body will give rise to fever and shock.

Answer 125

Gram-negative

Answer 126

* LPS binds to TLR4 on monocytes (with the help of CD14) * This leads to systemic release of TNF-α, IL-1, IL-6 & IL-8 * This leads to fever, endothelial damage, capillary leakage and hypotension * This leads to systemic activation of the coagulation cascade (DIC) * Overall, this leads to hypoperfusion and therefore multiorgan system failure (Note: Other TLR ligands can also lead to sepsis)

Answer 127

It is another name for septic shock -\> It shows the importance of endotoxins in this process.

Answer 128

This shows that acute inflammation on a local scale is beneficial, while on a larger scale it can lead to systemic effects (e.g. fever). At very high levels, it leads to septic shock.

Answer 129

* TNF-α * IL-1 * IL-6 * IL-8 * NO * PAF

Answer 130

Note that this is not a complete list. Add some better flashcards on this.

Answer 131

TNF (tumour necrosis factor) inhibitors are highly effective in treating illnesses characterised by chronic inflammation, such as rheumatoid arthritis.

Answer 132

* Apoptosis * Necrosis * NETosis * Pyroptosis

Answer 133

* Infectious agents * Chemical agents * Oxygen deprivation * Physical agents (heat, radiation, trauma) * Genetic defects * Immune cell activation (CTL, ADCC) * Aging (cellular senescence)

Answer 134

* Loss of cell membrane integrity * Decreased ATP concentration * Protein unfolding and protein aggregation * Protein trafficking defects * Cation imbalance (Na+, Ca2+, H+) * Loss of integrity of the genome Note: The cellular response to injury depends upon the type of injury, its duration and its severity and the consequences of injury vary depending upon the cell type.

Answer 135

* ATP depletion -\> Leading to rapid shutdown of homeostatic pathways * Generation of Reactive Oxygen Species (ROS) -\> Activates multiple signalling pathways, kinases, phosphatases, NF-kB, phospholipases * Changes in membrane permeablility -\> Leads to breakdown of concentration gradients of ions and metabolites * Loss of calcium homeostasis * Mitochondrial damage

Answer 136

* Lysosomal catabolism - heterophagy and autophagy * Induction of smooth endoplasmic reticulum (p450) * Alterations in mitochondrial number and function * Abnormalities of cytoskeleton * Induction of stress proteins e.g. Heat Shock Proteins (HSPs) & other chaperones

Answer 137

* Autophagy is a cell survival mechanism that aims to derive energy by eliminating defective organelles. * It very rarely result in cell death. * It can be triggered in starvation and can delay or prevent programmed cell death.

Answer 138

In essence, a membrane forms around proteins, damaged organelles and pathogens in the cytosol. This creates an autophagosome. It fuses with a lysosome to release ATP and precursors for protein synthesis.

Answer 139

* If the proteins are not dealt with, they may lead to cell death * Thus, the proteins are either repaired using chaperone proteins, or they are tagged by ubiquitin and degraded using a proteasome

Answer 140

* Necrosis is a form of irreversible cell injury that leads to cell death by autolysis (self-digestion). * It is usually caused by external factors, such as trauma.

Answer 141

* Necrosis does not use an apoptotic pathways, but instead features external factors (e.g. trauma) that lead to irreversible cell damage * Damage to the cell leads to damage to the cell membrane and organelles, accompanies by an influx of calcium * This leads to the loss of cell components, denaturation of proteins and hydrolytic digestion of cell components, destroying the cell

Answer 142

* Liquefactive necrosis -\> Cell structure is destroyed by digestion, leading to the formation of a viscous liquid mass * Coagulative necrosis -\> Cell structure is intact, but there is coagulation due to to protein degradation, where albumin tranforms into a firm state. * Caseous necrosis -\> A combination of coagulative and liquefactive necrosis, with incomplete digestion leaving behind granular particles. * Fat necrosis -\> Associated with acute pancreatitis.

Answer 143

* Necrosis: damage to the cell raises intracellular calcium and activates hydrolytic enzymes. * Result: Cell death and the release of inflammatory mediators.

Answer 144

The appearance of its nucleus.

Answer 145

Apoptotic: * Macrophage detects apoptotic cell using scavenger receptors and phosphatidyl serine receptors, which detect ligands in the membrane that have been exposed by blebbing * This leads to changes in gene expression that are more anti-inflammatory (or no changes) Necrotic: * Macrophage detects necrotic cell using Fc receptors and immmunoglobulin receptors, which detect opsonins that mark out the necrosed cell * This leads to changes in gene expression that are more pro-inflammatory

Answer 146

Add more flashcards on this!

Answer 147

Intrinsic pathway: * Non-receptor mediated: Various stimuli (e.g. DNA damage) lead to eventual release of cytochrome c from mitochondria * Activates caspases * Leads to cell death Extrinsic pathway: * Receptor-mediated: Stimulation of death receptors by death receptor ligands leads to signalling cascade * Activates caspases * Leads to cell death Think of the caspase as the common end goal of these pathways. They can either be triggered by ligands that bind to receptors, or some sort of cell damage (or other change) which lead to release of cytochrome c from mitochondria.

Answer 148

There is release of inflammatory mediators, which can attract phagocytes, etc. However, these can lead to damage of surrounding tissue, so that the process is renewed and is self-reinforcing.

Answer 149

They both trigger the extrinsic apoptotic pathway: * Signalling via the TNF receptor and FAS receptor leads to activation of proteins with a FADD (FAS-associated death domain) * This FADD cleaves pro-caspase 8 into caspase 8, which in turn leaves pro-caspase 3 into caspase 3. * Activated caspase 3 cleaves I-CAD (the inhibitor of CAD) * CAD then enters the nucleus and cleaves DNA

Answer 150

Programmed cell death, which is controlled and done in an orderly fashion.

Answer 151

* It can be developmentally programmed * Lack of a specific growth factor * Unrepaired DNA damage

Answer 152

Apoptosis: * Controlled * Cells play an active role (cell suicide) * Does not lead to cell lysis and release of inflammatory mediators Necrosis: * Uncontrolled * Cells are more passive * Leads to cell lysis and release of inflammatory mediators

Answer 153

You can see how there are the extrinsic pathway (via receptor-ligand interactions) and the intrinsic pathway (via all the other number 1s). They all ultimately lead to executioner caspase activation, although these caspases can be regulated by various mitochondrial regulators. The caspases lead to DNA fragmentation, cytoskeleton breakdown, and formation of apoptotic bodies that are broken down by macrophages.

Answer 154

* TNF-α activating the TNF receptor * FAS ligand activating the FAS receptor * Cytotoxic T-cell granule release

Answer 155

FAS signalling explains the concept of immune privileged sites (in some cases): * Cells in immune-privileged sites (such as in the eye) expressed FAS ligand. This binds to the FAS receptor of any incoming T-cells, causing them to die by apoptosis. * Some cancers make use of this immune privilege by also expressing FAS ligand, so that T cells cannot target them

Answer 156

The common end to the intrinsic and extrinsic pathways of apoptosis are the executioner caspases. These are under the control of various mitochondrial regulators.

Answer 157

* The executioner caspases lead to endonuclease activation (leading to degradation of DNA) and catabolism of the cytoskeleton. * DNA fragments and organelles are packed into cytoplasmic buds (blebbing), known as apoptotic bodies, which are dealt with by macrophages (without release of inflammatory mediators)

Answer 158

* Bcl-2 is an inhibitory regulator of the caspase cascade in apoptosis * Thus, when it is upregulated, it can lead to development of cancers

Answer 159

* TLR and TNF receptor activation leads to increased transcription of pro-IL-1β, pro-IL-18 and inflammasome components. * The presence of PAMPs and DAMPs (e.g. in internalisation of pathogens) and mitochondrial dysfunction leads to the assembly and activation of the inflammasome * The inflammasome produces caspase-1, which cleaves the pro-IL-1β and pro-IL-18 into their active forms * Caspase-1, along with caspases 4 and 5, also cleaves gasdermin D * The cleaved gasdermin D can now form a pore through which the inflammatory cytokines and DAMPs can leave, leading to inflammation

Answer 160

* Activation of multiple proteolytic pathways. * Cytoskeletal changes -\> Forming apoptotic bodies. * Chromatin is broken down into 180-200bp fragments. * Cleavage of enzymes involved in DNA repair and replication.

Answer 161

* Normal tissue homeostasis * Embryonic morphogenesis * Deletion of self-reactive lymphocytes

Answer 162

* NETosis is a slow form of apoptosis seen in neutrophils. * It is characterized by the release of decondensed chromatin and granular contents to the extracellular space, forming a NET.

Answer 163

NET formation is triggered by innate immune receptors acting through intracellular mediators that include reactive oxygen species (ROS) produced by NADPH oxidase or mitochondria, which activate myeloperoxidase (MPO), neutrophil elastase (NE) and protein-arginine deiminase type 4 (PAD4) to promote chromatin decondensation.

Answer 164

* Capture pathogens * Degrade bacterial toxic factors * Kill bacteria * Prime other immune cells to induce inflammation * Occlude the vasculature by promoting thrombosis and obstruct important organ areas

Answer 165

A controlled form of cell necrosis that is highly inflammatory, since it releases cytokines and DAMPs.

Answer 166

* Necrosis is caused by physical or mechanical tissue injury -\> It is not controlled. * Pyroptosis is carried out in a deliberate and highly self-programmed process that generally involves innate immune cells and activation of inflammasomes.

Answer 167

Death of bacterially infected cells and the bacteria they contain.

Answer 168

* Cellular Senescence is a ‘permanent’ arrest of the cell division cycle. * It is associated with hyperactivated secretion of pro-inflammatory factors that affect a range of patho-physiological processes such as impaired wound healing, cancer and aging. * This behaviour of aging cells has been referred to as senescence-associated secretory phenotype (SASP).

Answer 169

Classic activation: * IFN-γ (in CLASSIC activation) * Endotoxins (LPS) Alternative activation: * IL-4 * IL-13

Answer 170

* Interferons (IFN) are cytokines that are released primarily in respones to viral infection (and tumours) * Thus they mostly activate the innate immune system -\> In particular, macrophages * The two types: * Type 1 interferons -\> IFN-α and IFN-β * Type 2 interferons -\> IFN-γ

Answer 171

Pro-inflammatory: * TNF-α * IL-1 * IL-6 Anti-inflammatory: * IL-10 * IL-12 They also produce IFN-α and IFN-β according to the spec

Answer 172

In chronic inflammation.

31. Cell Death and Repair, Inflammation, Anti-Inflammatories Flashcards

(218 cards)