L3 - Innate immunity 2

Question 1

INNATE IMMUNE CELLS

i) name one role of neutrophils and two things that they produce?
ii) name four things macrophages produce? what can this activate?
iii) which cell can antigen present? (2)
iv) what is the main role of NK cells? what two molecules does it release to do this? which other cells can they activate?
v) name two cell types that have both adaptive and innate qualities
vi) what are the two types of dendritic cell? what does each one produce/do?

Answer 1

i) ROS, antimicrobial peptides
- do phagocytosis

ii) macrophages produces inflam mediators, ROS, cytokines, complement proteins > activates complement cascade
iii) dendritic cells (myeloid) and macrophages can APC

iv) NK cells lyse viral infected cells
- release granzyme and perforin
- can also activate macrophages

v) adaptive and innate = GD T cells and NK cells (express PRRs)

vi) plasmacytoid dendritic > lymphoid and produces IFN
myeloid dendritic > APC and prod pro inflam cytokines

Question 2

PHAGOCYTE RECRUITMENT

i) name two things phagocytes release
ii) what action do cytokines have on local blood vessels? what two cell types do chemokines attract to site of infection?
iii) name two cell adhesion molecules that are upregulated on the endothelium? what do these bind?
iv) what are the four stages of phagocytes getting to site of infection?

Answer 2

i) release cyto and chemokines

ii) cytokines cause bv to dilate
- chemokines attract monocytes and neutrophils to infection

iii) ICAM1 and VCAM1 are upreg on the endothelium and bind integrins on leucocytes in the blood

iv) phagocyte rolls > activates >
arrest/adhesion > transendothelial migration

Question 3

PHAGOCYTOSIS

i) name three cells it is performed by?
ii) what is it?
iii) what do opsonins do? name three things that opsonise?
iv) name four phagocytic receptors and what they bind to
v) what do scavenger receptors bind to? what do they recognise? (3)

Answer 3

i) neutrophils, dendritic cells, macrophages
ii) capture and digestion of a foreign particle

iii) opsonins highlight molecules to be phagocytosed and engage with receptors on phagocytic cells
- complement components (C3b), collectins (MBL), antibodies

iv) phago receptors = complement receptors, Fc receptors (for antibodies), mannose R (for MBL), scavenger receptors

v) scavenger receptors bind to lipid
- they recognise bacteria, viruses and apoptotic cells

Question 4

RECEPTOR MEDIATED PHAGOCYTOSIS

i) what do phagocytic receptors bind?
ii) by what mechanism are pathogens internalised?
iii) once internalised - what forms? how does this degrade the microorganism?

Answer 4

i) phago receptors bind opsonins
ii) receptor mediated endocytosis

iii) once inside > phagolysosome (fusion of endosome and lysososome)
- bacteriocidal enviro inside the phagolyso causes MO to be degraded

Question 5

ANTIMICROBIAL MECHANISMS OF PHAGOCYTES

i) what pH are products from MPs/neutrophils?
ii) name three toxic oxygen derived products? what do these do?
iii) name two antimicrobial peptides produced by macrophages? and two produced by neutrophils?
iv) what role does lyosozyme play?
v) name two competitors that stop bacterial growth

Answer 5

i) pH 3.5-4

ii) superoxide, hydrogen perioxide, singlet oxygen
- these can break down pathogens

iii) MP > cathelicidin, macrophage elastase derived peptide
NP > defensins, cathelicidin

iv) lysozyme digest cells walls of some gram positive bacteria (peptidoglycan)
v) competitors > lactoferrin and vitamin B12 binding protein

Question 6

NEUTROPHIL EXTRACELLULAR TRAPS

i) what is NETosis?
ii) what is released during NETosis? what does this do?

Answer 6

i) a special form of cell death that some neutrophils under go

ii) nuclear chromatin is released from cells
- this traps MOs and aids phagocytosis

Question 7

PATTERN RECOGNITION RECEPTORS

i) where are C type lectin receptors found?
ii) name two places TLRs are found?
iii) name three PRRs that are found in the cytosol? which type of pathogens may these target
iv) what do these receptors recognise? what are these called?

Answer 7

i) C type lectin receptors are found on the cell surface
ii) TLRs found on cell surface and on the surface of the endosome

iii) PRRs in the cytosol - NOD like receptors (NLRs), Rig I like receptors (RLRs), cytosolic DNA sensors (CDS)
- may target viruses as they can get into cytosol

iv) receptors recognise conserved structures = PAMPs
(pathogen associated molecular patterns)

Question 8

PATTERN ASSOCIATED MOLECULAR PATTERNS

i) what are they? can the pathogen exist without them?
ii) why must the innate immune system focus on PAMPs? give two examples of a PAMP
iii) what is a damage associated molecule pattern?
iv) are PAMPs always on pathogenic bacteria?
v) what occurs in microbes thay plays a role in their ability to survive and adapt?

Answer 8

i) highly conserved elements that the pathogen cannot live without

ii) innate imm sys must focus on PAMPs as microbes evolve rapidly
- cell wall structures and nucleic acids

iii) DAMP = molecules released from necrotic cells
iv) no - can be on gut bacteria etc (MAMPs)
v) random mutations

Question 9

C TYPE LECTIN RECEPTORS

i) where are they expressed?
ii) what do they bind to? what does this depend on?
iii) what do type I CLRs assist with? what are type II CLRs involved in?

iv) name a soluble CLR - what does this bind on the pathogen?
- name two other things this receptor can do

Answer 9

i) by most cell types that phagocytose glycoprotein and microbes
ii) bind to carbohydrates in a calcium dependent mannor

iii) type I > antigen uptake by phagocytes
type II > fungal recogition

iv) soluble CLR = MBL
- binds carbohydrate on pathogen surfaces
- also activates complement and induces phago by acting as an opsonin

Question 10

TOLL LIKE RECEPTORS - STRUCTURE

i) which organism were these receptors discovered in? which two types of infections developed when the organism was deficient in these receptors?
ii) what domain does the extracellular part contain? what is this the site of?
iii) once activated - which domain is there a conformational change in? how many amino acids make up this domain?

Answer 10

i) drosophila
- developed bacterial and fungal infections when deficient

ii) extracell domain = LRR (leucine rich repeats) which is the site of pathogen binding (engages PAMP, DAMP)

iii) activation > conform change in TIR intracell domain
- TIR domain = 200 amino acids conserved across all TLRs

Question 11

TLR FUNCTIONAL DIMERS

i) what has to happen for the triggering of signal activity?
ii) which two type of dimers can be formed? what does this affect?
iii) what do TLRs bind to induce dimerisation? what is brought close when dimerisation occurs?

Answer 11

i) need TLR to come together in a pair and two TIR domains brought close

ii) form homo (2 receptors of same subtype) or heterodimers
- affects downstream signalling and what ligands they bind

iii) TLRs bind the lipid side change on a lipopeptide
- two TLRs must bind the same lipopeptide to induce dimerisation and bring TIR domains close together

Question 12

TLRS - CELLULAR LOCATION

i) how many TLRs are there in humans?
ii) where are most TLRs found? where are some also found? what do they recognise here?
iii) what happens in the endosome? name three things that TLRs will recognise here?
iv) which TLR is TLR10 in competition with? why?

Answer 12

i) 10

ii) most are found on the cell surface (recog lipopeptidesm flagellin and LPS)
- some found on the endosome - recog nuc acid structures

iii) endosome = pathogen is broken down & gen mat exposed
- TLR can recog dsRNA, ss RNA and CpG DNA

iv) TLR10 is in competition with TLR 3 as they both recognise dsRNA

Question 13

WHAT DO TLRS RECOGNISE?

i) which TLRs are found on the cell surface? what do these mainly recognise?
ii) which TLRs are found on the endosomal surface? what do these mainly recognise?
iii) which host/DAMP molecules do cell surface TLRs recognise?
iv) which host/DAMP molecules do endosomal TLRs recognise?
v) what can complement deficiency result in? what does this cause in relation to TLRs? what molecule is released?

Answer 13

i) TLR 1,2,4,5,6
- recognise bacterial products eg LPS

ii) TLR 3,7,8,9,10
- mainly recognise viral products eg dsRNA

iii) cell surface TLRs recog protein/lipid from host eg HSP70
iv) endosomal TLRs recog host DNA/RNA

v) complement defic > autoantibodies that are not cleared and bound to own DNA and RNA
- taken up by immune cells and trigger TLRs in the endosome to release IFN = classic of lupus

Question 14

TLR SIGNALLING CASCADE

i) which four adaptor proteins can be used ds of TLRs? which TLR uses all four?
ii) what adaptor protein do most TLRs engage with? which two pathways does this drive? what is ultimately produced?
iii) why type of cytokines does TLR signalling induce gene expression of?
iv) name two molecules that can be upregulated following TLR activation
v) name two things that can be released following TLR activation
vi) which downstream pathway activates IFN? which pathway activates interleukins?

Answer 14

i) Trif, TRAM, MYD88, Mal
- TLR4 uses all of them

ii) most TLRs engage with MyD88
- this drives NFKb and AP1 which ultimately activated interleukins

iii) TLRs induce expression of pro inflammatory cytokines
iv) upregulation of MHC and co-stimulatory molecules
v) release of antimicrobial peptides and complement components

vi) Trif pathway > IFN
MyD88 pway > interleukins

Question 15

MYD88 GOF MUTATION

i) what is waldenstrom macroglobulinemia?
ii) what % of these patients have a MyD88 mutation? what does this cause?
iii) which Ig do B cells make large amounts of? name three things this can cause
iv) name three things that lymphoma cells proliferating in the BM can cause?

Answer 15

i) a rare type of non hodgkins lymphoma

ii) 90% of patients have MyD88 mutation
- causes cell growth and survival

iii) B cells make lots of IgM which causes excess bleeding, vision problems and headaches
iv) prolif lymphoma cells can cause anaemia, neutropenia and thrombocytopenia

Question 16

MYD88 DEFICIENCY

i) can you live without it?
ii) in a study - what did MyD88 defic children suffer from? how was their resistance to microbes?
iii) what did clinical status improve with? give a suggestion of the mechanism of this?

Answer 16

i) yes

ii) children had recurrent pyogenic bacterial infections (pneumonia/s.aureus infec)
- normal resistance to microbes and otherwise well

iii) clinical status improved with age
- compensatory effect of adaptive immunity (as this improves with age)

Question 17

IMPORTANCE OF TLRs

i) deficiency in which TLR is the only one to be linked to immunodeficiency?
ii) which virus does deficiency in this TLR predispose to? what type of virus is this?

Answer 17

i) TLR3

ii) linked to herpes simplex encephalitis (HSE)
- inflammation in the brain
- dsDNA virus that prodces dsRNA during replication

Question 18

TLRS IN DISEASE

i) name four diseases that activate TLR2 and TLR4?
ii) name a TLR agonist that can be used for treatment of genital warts and melanoma? what TLR does it agonise?
iii) what environmental agent can be used to tolerise against an allergen? which TLR does it work on?
iv) in what situation would you want to antagonise TLR activity? (2)
v) what three TLRs does SLE activate? where are these found?

Answer 18

i) alzheimers, atheroscleoris, sepsis, tb
ii) aldara > agonises TLR7
iii) ragweed pollen can tolerise against allergens and works on TLR9
iv) antagonise in autoimmunity and sepsis
v) SLE > TLR 7,8,9 (endosomal)

Question 19

NOD LIKE RECEPTORS (NLRs)

i) what repeats do they have in them? what do these interact with?
ii) where are they exclusively found?
iii) what are the two main groups?

Answer 19

i) leucine rich repeats that interact with PAMPs
ii) exclusively found in the cytoplasm
iii) NLRCs and NLRPs

Question 20

NLRCs

i) give two examples of receptors in this family
ii) what does the C stand for?
iii) which amino acid is rich in the domain? what does this bind?
iv) which domain is used to signal? what does this produce (2)

Answer 20

i) NOD1 and NOD2
ii) C = caspase recruitment domain
iii) leucine rich domain that binds peptidoglycan in bacteria
iv) CARD domain used to signal > NFKb and cytokine prod

Question 21

NOD1 AND NOD2

i) what do they detect?
ii) what does NOD1 bind? which type of bacteria is this found in?
iii) what does NOD2 bind? what type of bacteria is this found in?
iv) what is NOD2 GOF mutation linked to? what happens in this condition?
v) what is NOD2 LOF mutation associated with?

Answer 21

i) similar yet distinct peptides of peptidoglycan
ii) NOD1 binds iE DAP - mainly found in gram neg bacteria
iii) NO2 binds muramyl dipeptide - found in gram + and -
iv) NOD2 GOF linked to sarcoidosis (AI) > granulomas develop in organs of the body
v) NOD2 LOF > chrohns disease suceptibility

Question 22

NLRPs

i) which one is best characterised? what is this activated by? (give three examples)
ii) which two things does it come together with to form the inflammasome?
iii) what is the inflammasome essential for?
iv) what is formed in lots of conditions that activates the inflammasome? give four example of diseases

Answer 22

i) NLRP3 > activated by cellular stress eg K+ efflux, ATP and ROS
ii) comes together with caspase 1 and ASC > inflammasome
iii) inflammasome is essential for IL-1 and IL-18 secretion

iv) formation of crystals > activates IS
- gout, asbestos, silica, alz (amyloid beta), malaria (hemozoin crystals), type II diabetes

Question 23

INFLAMMASOME

i) what happens in frustrated phagocytosis? what gets activated? what does this cause?
ii) which two pro interleukins does the inflammasome cause cleavage of?
ii) which transcription factor drives transcription of IL-1b? what is this made as? which inflammosome proteins cleaves it?

Answer 23

i) macrophage tries to break something down and the MP gets stuck which activates the inflammasome
- this causes interleukin activation and increased inflammation

ii) pro IL-1 and pro IL-18

iii) Nfkb drives transcription of IL-1b
- made as pro IL-1 and cleaved by caspase 1 from the inflammosome

Question 24

GOF MUTATION IN NLRP3

i) what happens when there is GOF in NLRP3?
ii) CAPS syndrome is caused by a rare mutation in which exon of NLRP3? what does this cause?
iii) what can trigger Muckle Well Syndrome? (3) give four symptoms
iv) what is familial cold autoinflam syndrome caused by? what does this trigger? give four symptoms
v) what can both conditions be treated with? what does this drug do?

Answer 24

i) lots of production of IL-1

ii) CAPS syndrome caused by mutation in exon 3 of NLRP3
- causes over production of IL-1

iii) muckle well - spontaneous, cold, heat, fatigue, other stress
- fever, rash, arthralgia, conjunctivitis, life threat amyloidosis

iv) familial cold autoinflam syndrome caused by exposure to cold > triggers NALP3 inflammosome > prod IL-1
- fever, uriticarial rash, headache, arthralgia

v) both conditions can be treated with anakinra
- antagonises IL-1

Question 25

RIG I LIKE RECEPTORS - RIG1 AND MDA5

i) where are they found? what do they sense? why is this relevant?
ii) what do they signal to produce? (2)
iii) what does RIG I bind to? why does it not recognise self cells?
iv) what does MDA5 preferentially recognise? what is it critical for detection of?
v) what have mutations in MDA5 been associated with? (2)

Answer 25

i) found in the cytosol and sense cytoplasmic RNA
- RNA is an intermediate for viruses

ii) signal to produce pro inflammatory cytokines and IFN

iii) RIG I binds to ssRNA containing 5’triphos
- doesnt bind our cells as 5’ RNA is capped so cant be recog

iv) MDA5 preferentially recog long dsRNA
- critical for detection of picornavirus

v) mutations in MDA5 have been assoc with IFN related disease such as SLE and aicardi goutier syndrome

Question 26

CYTOSOLIC DNA SENSORS

i) name two cytosolic DNA sensors
ii) what does viral dsDNA bind? what does this cause the production of?
iii) what is the ligand for STING? what happens when STING binds its ligand?
iv) what does a GOF mutation in sting cause?
v) what type of disease is SAVI? what is it caused by? what do patients produce too much of? what does this cause?
vi) how may bacteria directly activate the STING pathway? what do they release?

Answer 26

i) cGAS and STING
ii) viral dsDNA binds cGAS which causes it to convert ATP and GTP to cGAMP > ligand for sting

iii) cGAMP is ligand for STING
- binds and signals to produce IFN alpha and beta

iv) GOF mutation in STING causes lots of IFN alpha to be produced

v) SAVI (stimulator of interferon genes assoc vasculopathy onset infancy) is an autoinflammatory disease caused by GOF mut in gene coding for STING
- patient produces too much type I IFN > abnormal inflammation through body (skin, bv and lungs)

vi) bacteria can release cyclic dinucleos such as cdiGMP and CdiAMP that directly activate STING

Question 27

ACUTE PHASE RESPONSE

i) where are acute phase proteins mainly produced?
ii) name three things that APPs are induced by? what situations does this happen in? (2)
iii) what can APPs actvate? what does this induce?
iv) name two parameters that are characteristic of an acute phase response? what are these used clinically to detect?
v) name four APPs

Answer 27

i) in the liver

ii) cytokines such as TNF, IL-6 and IL-1
- happens in infection and inflammation

iii) APPs can activate complement and induce opsonisation and phagocytosis

iv) CRP and raised erythrocyte sedimentation rate
- clinically detect inflammation

v) serum amyloid protein, CRP, fibrinogen, MBL