L13 Immune defence Flashcards by Yasmin Yau

what are the pathogens were exposed to

bacteria
viruses
parasites
fungi

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what is involved in innate immunity

complement
macrophages/neutrophils
eosinophils
mast cells

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what is the role of complement

opsonisation
cellular recruitment
lysis

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what is the role of macrophages/neutrophils

phagocytosis

intracellular digestion

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what is the role of eosinophils

extracellular digestion

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what is the role of mast cells

inflammation

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what is involved in adaptive immunity

B cells

T cells

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what is the role of B cells

immunoglobulin production

antibody mediated/humoral

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what is the role of T cells

helper T cells
cytotoxic T cells
(cell mediated)

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what are the three pathways

classical
lectin
alternative

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which pathways are antibody independent

lectin

alternative

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which pathways are antibody dependent

classical

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what do the three pathways do

activate C3 and generation of C5 convertase

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what does C5 convertase do

lytic attack pathway

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what happens in the classic pathway

antibody bind to specific antigen on pathogen surface

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what happens in the lectin pathway

mannose binding lectin binds to pathogen surface

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what happens in the alternative pathway

pathogen surface makes local environment conductive to complement activation

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what happens when complement activated

C3b covalently bound to surface compounds of pathogen

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what happens when C3b binds to pathogen

death of pathogen by:
recruitment of inflammatory cells
opsonise pathogen
perforation of pathogen membrane

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what are the physiological complement activation consequences

lysis of bacteria
chemotaxis of phagocyte
opsonisation of bacteria

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what happens in macrophage killing

bacteria bind to endocytic receptors of macrophages
engulfment and degradation
bacterial components binding to signalling receptors of macrophages induce inflammatory cytokines

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what happens in neutrophil killing

neutrophil expresses receptors for many bacterial constituents neutrophils engulf and digest bacteria they bind to

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where is macrophage killing

intracellular

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where is neutrophil killing

intracellular

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what are the macrophage and neutrophil bactericidal agents

``` acidification toxic oxygen derived products toxic nitrogen oxides antimicrobial peptides enzymes competitors ```

what pH is macrophage and neutrophils acidification

3.5-4

what are they toxic oxygen derived products of macrophage and neutrophils

``` superoxide O2- hydrogen peroxide H2O2 singlet oxygen 1O2* hydroxyl radical OH* hypohalite OCI ```

what are the toxic nitrogen oxides of macrophage and neutrophils

nitric oxide NO

what are the antimicrobial peptides of macrophage and neutrophils

defensins | cationic proteins

what are the enzymes of macrophage and neutrophils

NAPDH dependent oxidases lysozyme acid hydrolases

what are the competitors of macrophage and neutrophils

lactoferrin (binds Fe) and vitamin V12 binding proteins

where is eosinophil killing

extracellular

what are the preformed and newly synthesised products of eosinophils

``` enzymes toxic protein cytokine chemokine lipid mediator ```

what are the preformed and newly synthesised proteins of eosinophils products

eosinophil peroxide | eosinophil collagenase

what do eosinophil peroxide do

toxic to target by catalysing halogenation | trigger histamine release by mast cells

what do eosinophil collagenase do

remodel connective tissue matrix

what are the preformed and newly synthesised toxic proteins of eosinophils products

major basic protein eosinophil cationic protein eosinophil derived neurotoxin

what are the biological effects of major basic protein for eosinophils

toxic to parasites and mammalian cells | triggers histamine release by amst cells

what are the biological effects of eosinophil cationic protein

toxic to parasite | neurotoxin

what are the biological effects of eosinophil derived neurotoxin

neurotoxin

what are the cytokines from eosinophils

IL3 IL5 GM-CSF

what do the eosinophil cytokines do

amplify eosinophil production by bone marrow | cause eosinophil activation

what are the eosinophil chemokines

CXCL8

what do the eosinophil and chemokines do

promote leukocyte influx

what are the lipid mediators of eosinophils

leukotrienes C4, D4 and E4 | platelet activating factor

what do eosinophil leukotrienes C4, D4 and E4 do

cause smooth muscle contraction increase vascular permeability cause mucus secretion

what do eosinophil platelet activating factor do

chemotatic to leukocytes amplify lipid mediator production activate neutrophils, eosinophils and platelets

what are the products of a mast cell

``` enzyme toxic mediator cytokine chemokine lipid mediator ```

what are the mast cell enzymes

tryptase chymase cathepsin G carboxypeptidase

what is the biological effect of mast cell enzymes

remodel connective tissue matrix

what are the toxic mediators of mast cells

histamine | herapin

what is the biological effect of mast cell toxic mediators

toxic to parasite increase vascular permeability cause smooth muscle contraction

what are the mast cell cytokines

TNF-alpha IL4, IL13 IL3, IL5, GM-CSF

what are the mast cell TNF-alpha biological effects

promote inflammation | stimulate cytokine production

what are the mast cell IL4 and IL13 biological effects

stimulate and amplify Th2 cell response

what are the IL3, Il5 and GM-CSF

promote eosinophil production and activation

what are the mast cell chemokines

CCL3

what is the biological effect of mast cell chemokines

chemotatic for monocytes, macrophafes and neutrophils

what are the mast cell lipid mediators

leukotrienes C4, D4 and E4 | platelet activating factor

what is the biological effect of mast cell leukotrienes

smooth muscle contraction increase vascular permeability mucus secretion

what is the biological effect of mast cell platelet activating factor

chemotactic for leukocytes amplify lipid mediator production activate neutrophils, eosinophils and platelets

what are the two adaptive immunities

cell mediated | humoral

what happens to bacterial toxins

neutralisation | ingestion by macrophage

what happens to bacteria in extracellular space

opsonisation | ingestion by parasite

what happens to bacteria in plasma

complement activation | lysis and ingestion

what happens in antibody dependent cell mediated cytotoxicity

antibody binds antigens on target cell surface Fc receptors on NK recognise bound antibody crosslinking Fc receptors signal NK to kill - apopotosis

what is ADCC

antibody dependent cell mediated cytotoxicity

what is involved in cell mediated immunity

CD4 TH1 cell and macrophage cytokines activated macrophage

what is involved in humoral immunity

CD4 TH2 and B cell cytokines plasma cell and antibodies

what does cytotoxic T cell recognise

complex of viral peptide with MHCI and kills infected cell

what are the cytotoxic effector moleucles

perforin granzymes granulysin Fas ligand

what are the immune responses

extracellular infection intracellular vesicular infection intracellular cytosolic infection

what happens in extra cellular infection

Innate immune response activated Complement activation and phagocytosis At the same time info on the pathogen transported via lymphatic system to local lymphoid organ Naïve B cells and T cells that are activated recirculate B cells make antibodies T cells activated and effector cells – help clear pathogen

what happens in intra cellular vesicle infection

Interferons and NK cells (innate immune response) Info taken to local lymphoid tissue Activation of Th1 and CD8 cytotoxic T cells Recirculate and kill virally infected cells

what happens in intra cellular cytosolic infection

Phagocytes have already ingested the pathogen Info on the pathogen taken to local lymphoid organ Need cell mediated response (Th1) Th1 activated and recirculate to infection site – make cytokine signals to activate macrophages to better intracellularly digest