Immunology Flashcards

Question

Signalling function of BCRs

Answer 1

Syk and Lyn kinases recruited + actvivated to form signalosome -> can activate various downstream signalling pathways (RAS/RAF & Nf-KB/NFAT) - Signalling determines fate of antigen-encountered B cells - Modulates gene expression, adhesion or survival - Differentiate into plasma B cell ## Footnote Syk mediates IP3 generation, whereas Lyn regulates Ca2+ mobilization through a process independent of IP3 generation.

Answer 2

Produced on B cell surface or secreted (plasma cells) - antigen selectively activates virgin lymphocyte - clonal proliferation - maturation into effector plasma cells & memory cells

Answer 3

Heterodimers: 2 identical light (25 kDa) + 2 identical heavy (50 kDa) chains joined by disuphide bonds. 2 Fab regions (fragment antigen binding) Fc - fragment crystallisable -> effector domain Papain can cleave disulphide bonds linking heavy chains (Fab can bind antigen but Fc does not - but can be crsytallised) ## Footnote Immunglobinds so have Ig domain

Answer 4

N-terminal, have variable (H) and variable (L) at each binding site -> Fv Hinge region -> flexibility for antigen binding Hypervariable regions form complementary dtermining region (CDR) - mst be comp to antigenic epitope

Answer 5

Immune response inducing molecule recognised by Abs - commonly proteins but can be polysaccahrides, lipids, DNA etc. Epitopes - fragments on Ag recognised by Ab e.g. SARS-Cov2 epitopes are spike proteins - an antigen can have multiple different epitopes

Answer 6

Conformational: - Structural, formed by protein folding but may not be a continuous sequence of a. acids. - Most commonly recognised by Abs Linear: - Continuous sequence of a. acids - Less common - used in Western Blotting after protein denaturation

Answer 7

Yes - may share seuqence/structural homology, common epitopes. Myriad of antibodies produced during infection to recognise many different epitopes

Answer 8

Strength of binding between an epitope & an antibody antigen binding site. - Interactions are weak unless 2 binding mols are close together ## Footnote Binding forces are non-convalent - varied affinities

Answer 9

Same Ab can bind different epitopes - affinity will be less than for original.

Answer 10

Strength of an Ab-Ag complex. - If an antibody is using both binding sites to bind 2 epitopes on same antigen then avidity is increased Repeating epitopes can increase potential avidity

Answer 11

Antibody: - acquired after pathogen exposure - pathogen specific - memory -> 2nd response bigger + faster Innate: - immediate, pre-existing - Non-specific for any pathogen - No memory: 2nd response same as 1st

Answer 12

- neutralisation - opsonization - complement activation - Ab dependent cell mediated cytotoxicity (ADCC)

Answer 13

- Antibodies prevent pathogen/protein binding to their target - Important in protection against virus, prevents entry into cell + replication e.g. vaccines ## Footnote All 4 IgGs & IgA

Answer 14

Pathogen is tagged by antibodies for phagocytosis by macrophage/neutrophils. - Fc domain binds Fc receptor on phagocyte -> trigger ## Footnote IgG1, IgG3

Answer 15

Antibodies attached to surface of pathogen activate 1st protein in complement system. Can lead to: 1) Deposit complement proteins on surface of bacterium -> leads to pore formation + lysis of bacterium directly 2) Complement receptors on phagocytes recognise these comp proteins + induce phagocytosis ## Footnote IgM, IgG1, IgG3

Answer 16

Viral infected host cells can express viral surface proteins. - recognised by specific Abs - NKCs/macrophages w/ Fc receptors bind Ab (cross-link), killing target cell by perforin + granzymes release ## Footnote Mediates extracellular killing via apoptosis - IgG1 & IgG2

Answer 17

Agglutination - Ab ability to immunoprecipitate a coluble or non-soluble antigen A & B transferases encoded by ABO gene. Agglutination + hemolysis of RBC caused by variable antibody binding. ## Footnote AB is universal recipient, O is universal donor

Answer 18

Type depends on C region of heavy chains - class specific. Designed for - bindinf Fc receptors, complement actvation, secretion regulation.

Answer 19

IgG: most common, 4 classes, IgG1 most common IgM: earliest Ab made after antigen contact, pentamer via J chain & disulphide bonds, up to 10 binding sites IgD: rare, function unclear IgA1: serum & major Ig in mucosa, 2 subclasses, different structure in secretions: 2 Ig mols joined IgE: lowest in serum, activates mast cells, important for allergies + worm infection

Answer 20

IgM - pentameric via J chain & disulphde bonds (up to 10 binding sites) IgA - dimeric, 2 Ig mols joined via J chain

Answer 21

Useful for transport from lamina propria across epithelium into gut. - bind to receptor on basolaterla face of ep cell - endocytose - transcytosis to apical face of ep cell - IgA dimer + secretory component released at apical face of ep cell ## Footnote Dimers (IgA) predominant in external secretion, at mem surfaces

Answer 22

Another secondary lymphoid tissue - site of B cell activity (esp in gut)

Answer 23

CD8 - Tc/CTL CD4 - Th ## Footnote Both from thymus - declining function w/ age (it involutes)

Answer 24

a & B chain - variable + constant regions. Also has hinge (linked by S-S), TM & cytoplasmic tail domains (ITAMs) Has CDR from vriable region that binds antigen. Associated with CD3 receptors - mediates intracellular signalling

Answer 25

MUST be presented via APC, indirect binding to processed antigen presented by MHC mol

Answer 26

Antigen presenting molecule - coded by genes arrayed in long continuous DNA sgement. HLA (human leukocyte antigen) in humans, mouse H-2, rats RT1. They binds antigenic peptides & present them on surface to T cells.

Answer 27

- long a-chain (3 domains) bound to membrane + non-covalently linked to 2B chain - Only 1 TM domain (a-chain) - found on most nucleated cells It binds 8-10 a.acid peptides, direct CD8+ response

Answer 28

- shorter a-chain non-covalently linked to equal B-chain - 2 TM domains from both chains - restricted expression (macrophages, B cells, dendriitc cells) Binds 12-20+ a.acid peptides, direct CD4+ response

Answer 29

Polygenic - several different class I & II genes (III not for antigen presentation) contribute to phenotype Polymorphic peptide binding region - multiple variants of each gene within population -> hundreds of forms means different phenotypes

Answer 30

MHC-I: - a-chain encoded by A, B & C loci in humans - B2-microglobulin encoded by gene on different chrom (12 instead of HLA on Chr6) MHC-II: - a & b-chains encoded by DP, DQ & DR regions of HLA in humans

Answer 31

Inherent maternal + paternal gene products expressed equally in a cell SO most individuals are heterozygous -> advantageous for processing wider antigenic range. ## Footnote Processed Ag peptides are small fragements (7-18 a.acids)

Answer 32

Proteosome degrades antigen + peptides transported by TAP to rER. p88 (calnexin) dissociates from MHC-I in rER when peptide bound | TAP - transporter associated with antigen processing ## Footnote Class-I -> presentation of intracellular antigens (viral)

Answer 33

- partially folded a-chains bind calnexin (p88) until B2-microglobulin binds. - MHC complex released from calnexin, binds chaperone proteins (calreticulin & tapasin) & to TAP-1 - antigens processed + delivered via TAP to MHC-I mol - MHC-I completes folding + released from TAp complex & exported

Answer 34

- antigen endocytosed, froms endolysosome - antigen degraded by lyosozymes - MHC synthesised in rER w/ associated peptide-invariant chain - MHC fuses w/ endolysosome + invariant chain degraded & replaced by antigenic peptides - MHC/peptide exported to cell surface -> presentation

Answer 35

Prevents other proteins in ER from binding MHC-II, reducing autoimmune risk. Cleaved in acidified endosome, leaving CLIP still bound blocking peptide binding. HLA-DM binds MHC-II & releases CLIP -> MHC-II binds antigen & exported

Answer 36

TCR binds both antigen & MHC -> specificity determined by both antigenic epitope & MHC structure (a2-a1 or a1-B1) -> MHC restricts recognition to highly specific TCRs

Answer 37

Accessory role in strengthening TCR interactions CD4 - recognise antigen on MHC-II (binds B2 domain) CD8- recognise antigen on MHC-I (binds a3 domain) Enhance affinity of TCR for peptide-MHC complexes

Answer 38

- Extra pathogen recognition mechanism - Recognising different parts of pathogen from antibody - Some peptides are from functional parts of protein (eg essential enzyme sequences) - Can detect antigen that is inside cells (ie CD8 T cell detecting Class I MHC-associated peptides) - Less scope for mutations in pathogens to avoid recognition

Answer 39

- Enable rare antigen-specific lymphocytes to encounter their antigen - Enable different types of antigen specific lymphocytes to make physical contact - Enable cells to go where they are needed (site of infection) -> requires cell movement to AND within tissue/organ

Answer 40

- collect lymphocytes/immune cells at sites likely to be infected - circulation & specialised sites of antigen capture to enable interaction

Answer 41

Primary tissues - lymphocytes develop, Ag independent (thymus, bone marrow) Secondary tissues - lymphocytes migrate to (lymph nodes, spleen, MALT) Lymphoid vessels connect tissues w/ lymph nodes + bloodstream - lymph fluid, lymphocytes + tissue dendritic cells - no pump pressure by muscles

Answer 42

Efferent - exit lymph nodes (away from node) Afferent - supplies lymph nodes (towards node) Drainage lymphoid system asspciated w/ most internal organs - BUT enriched at barrier mucosal surfaces e.g. adenoids + tonsils, Peyer's patches

Answer 43

Dendritic cells travel to lymph nodes via afferent. T & B cells activated (selection, differentiation + proliferation). Activated lymphocytes leave nodes via efferent lymphatic vessels to blood, then back to tissue

Answer 44

FALSE - its constant-> increases chance of interaction in peripheral lymph nodes. Can take 4-6 days if antigen is new to the system.

Answer 45

Highly spatially organised Cortex - B cell area contsining follicles Paracortex - T cell area Medulla - plasma cells, some T cells + macrophages Secondary follicle - site of intense, transient B cell proliferation during infection

Answer 46

Mucosal associated lymphoid tissue - has as many lymphocytes as rest of body. Also gut (G), nasal (N), bronchus (B) & skin (S) asscoiated Also found around specialised cells e.g. liver + reproductive tract

Answer 47

Sub-epithelial dome with no afferent lymphatics or APCs/lymphocytes draining in. M cells in epithelium allow direct antigen entry from gut to GALT. Activated cells move out of germinal centres via efferent lymphatics - drain to blood via thoracic duct.

Answer 48

Wrapped around immune cells - close interaction of gut lumen + dendritic/immune cells, movement across detected quickly.

Answer 49

Filters antigens from blood (no afferent lymphatics) - enables response toblood-borne pathogens. Blood -> splenic artery -> trabecular arteries -> central arteries -> arterioles -> red pulp -> periarteriole lymphoid sheath (PALS) Red pulp deals w/ old RBCs. White pulp areas -> immune function (has B cell follicle germinal centres & PALS) ## Footnote PALS - T cell activation area

Answer 50

HEV let lymphocytes leave bloodstream & enter lymph node

Answer 51

Adhesion molecules (organ region) Chemokines (specific location)

Answer 52

Selectin mediated adhesion Firm attachment Extravasation

Answer 53

- P selectin induced on vessels in response to e.g. Lueokotriene B4, C5a, histamine, TNFa, LPS - TNF & LPS also induce additional 2nd selectin (E-selectin) few hours after - Selectins recognised by sulphonated sialyl-Lewis X structure on immune cells -> mediates reversible movement /"rolling" (slows down)

Answer 54

- ICAM-1 + ICAM-2 induced on vessels by e.g. TNF-a (Nf-KB, ROS signalling) - Bind to LFA-1 & CR3 on leukocytes - Rolling stopped due to firm attachment of lymphocyte to blood vessel

Answer 55

- Leukocyte crosses endothelial wall, involves LFA-1/CR3 - CD3 interactions also facilitate this (on leukocyte + endothelial cells) - Movement also known as diapedesis

Answer 56

- L-selectin (all types of leukocyte) binds CD34 - LFA-1 integrin (T cells, monocytes, macrophages + dendritic cells) binds ICAM-1, 2-3 - VLA-4 binds VCAM-1 & vibronectin - CR3 binds ICAM-1 - PSGL-1 binds E- and P-selectin

Answer 57

Cytokines that control movement of cells CXCL8 (neutrophils) & CCL2 (monocytes + NK cells) produced at site of infection. Immune cells can move up chemokine gradient towards infectious pathogen. They draw in cells + also involved in activation/survival of those cells ## Footnote BUT broad chemokine range allows specific localisation of lymphocytes in lymph nodes.

Answer 58

CXCL8 - released by macrophages, attract neutrophils + mobilises naive T cells CCL2 - produced by Ep cells + stromal cells -> attracts monocytes

Answer 59

Lymph nodes to allow response to antigen. Dependent on L-selectin (CD62L) expression on naive T cells + P- & E-sleectin on endothelium. - occurs via HEV expression

Answer 60

Plasma cells differentiated from anitgen specific B cells. Have heterochromatic nucleus, lots of golgi + rER for Ab production.

Answer 61

They rearrange Ig genes in bone marrow - independent of antigen but needs stromal cells. Rearranged Ig expressed on mem as IgM - eliminated if self-reactive. Cells then mature -> begin to express IgD Mature B cells that leave bone marrow cannot secrete Ab

Answer 62

B cells require 2 signals to become activated (like T cells) - Signal 1 is recognition by antigen specific mem Ig mol - Signal 2 is often from an interacting CD4+ T cell (T cell dependent stimulation) ## Footnote CD40 (B) interacts w/ CD40L (T)

Answer 63

Bacterial polysaccahrides can deliver strong enough antige to activate B cells -> many antigens close together in repetetive mem No affinity maturation SO Ab not as strong or efficient

Answer 64

B cells in cortex. Drained antigens collected by macrophages in marginal zone of cortex -> allow conformational antigen recognition/presentation (no processing) > 1 B cell must be stimulated -> cross-linking

Answer 65

Region of B/T cell proliferation at cortex/paracrotex border in medullary cords. Some cells then migrate to primary follicle -> form germinal centres

Answer 66

B cell can express MHC-II -> process/present antigen. Specific Tfh can bind peptide deliver 2nd activation signal: TCR:BCR, CD40L:CD40, cytokine delivery (IL-4)

Answer 67

T cell adheres to B cell+ synthesises IL-4 & CD40 ligand. Th reorients cytoskeleton & secretory apparatus towards B cell. IL-4 released + confined to intercellular space -> taken up by B cells -> promotes proliferation at germinal centres, Ab isotype switching to IgG1 & IgE

Answer 68

Differentiated plasma cells secrete IgM - low affinity. B cells can undergo class switching e.g. reguated by IL-4, IL-5, IFN-y, TGF-B

Answer 69

Follicular dendritic cells (FDCs) form network in primary follicles - not DCs (not haematopoietic) Designed to hold Ag/Ab complexes on icosomes on their surface. FDCs hold antigen for extended period, Ab internalised by B cells -> germinal centre formation ## Footnote B cells proliferate rapidly in primary follicles.

Answer 70

B cells enter primary follicles + down regulate Ig receptors + proliferate extensively -> centroblasts Centroblasts (dark) - B cells expressing IgM Centrocytes (basal light) - proliferative Secondary B blasts (apical light) - differentiation of plasma + memory cells ## Footnote Surrounded by mantle zone - displaced mature B cells

Answer 71

- Centroblasts undergo hypermutation of H & L chains of their specific Ig molecule - This causes changes in structure of hypervariable regions of Ab, random process

Answer 72

- Centroblasts now stop dividing and re-express their surface Ig – now called centrocytes - move over the FDCs expressing antigen. If they bind antigen with high enough affinity they will receive a survival signal – if not they die!!! - Only the cells capable of secreting high affinity antibody survive - As immune response progresses, feweer Ag means increased competition -> highest affinity selected for ## Footnote Affinity increase of x10-100,000

Answer 73

B cell can change H chain constant region from u (IgM) to gamma (IgG), alpha (IgA) or epsilon (IgE). Variable regions remain constant so no change to affinity. ## Footnote Occurs during centroblast/centrocyte stage

Answer 74

CD4+ Th cells & cytokines. W/o CD40-CD40L -> only make IgM Cytokines can also ifluence quantity of Ab made.

Answer 75

IL-4 - induces IgG1 + IgE, inhibits IgM+ IgG3 + IgG2a IL-5 augments IgA production IFN-y - induces IgG3 + IgG2a, inhibits IgM + IgG1 + IgE TGF-B - induces IgG2b + IgA, inhibits IgM, IgG3

Answer 76

IL-21 + IL-4 -> IgG1 IL-13 + IL-4 -> IgE IL-10, IL-21 + TGF-B -> IgA

Answer 77

Survive long periods, undergone class switch + affinity maturation, very fast/efficient secondary response after repeated antigen detected. e.g. IgE binds mast cells to clear worm infection

Answer 78

Can be short or long lived. Some stay in nodes/spleen + secrete Ab for few weeks, others go to bone marrow + secrete for many months. - bone marrow main Ab source Very high secretion rate (>2000 molds per second)

Answer 79

Production of both occurs in apical light zone of germinal centre - If B cell interacts w/ CD4+ Tfh cell, binding of CD154 on Tfh cell to CD40 on B cell turns into memory B cell -> can leave lymph nodes + enter circulation ## Footnote Dont understand what determines phenotype.

Answer 80

Innate - germline encoded (inherited), pattern recognition receptors fro PAMPS, MAMPS + DAMPS Adaptive - somatically generated (multiple gene segments rearranged in limited number of genes in developing T/B cells) - highly diverse random reprtoire of potential specificities -> recognise more epitopes

Answer 81

Progeitors -> naive circulating lymphocytes (unique specificity) Upon useful epitope recognition, useful clone proliferated to combat threat. - memory cells also generated

Answer 82

Ab: recuited by FcR interactions of different soluble Ab isotypes T cells: require cell contact (MHC processing), or local secretion of cytokines

Answer 83

3 hypervariable regions (HV1-3) w/ matched end loop regions - can tolerate variability w/o structural damage HV regions form tight B-barrel -? antigen binding site

Answer 84

e.g. k-light chain gene (constant region) V and J (joining) segments undergo somatic recombination - different expression in B cells (due to gene rearrangement) -> clonal B cells w/ variable light chains, different binding properties CRD1+2 encoded by Vk, CDR3 encoded by Jk - recombination determines segments included.

Answer 85

Has another segment (D - diversity) 2 rearrangements occur sequentially - D->J, V-> DJ, VDJ = V exon, V D & J all contribute to CDR3 Imprecise joining adds more variability to recombination

Answer 86

Made of conserved heptamer, spacer (12/23) & a nonamer They flank V, D & J segments - link them together during recombination. Spacer is 12 or 23 base pairs, 12/23 rule -> 12 must bind 23, vice versa. SO Segments pulled together + RAG1/2 cleaves within heptamer, intervening sequences excised.

Answer 87

RAG1 + 2 turned on, segments pulled together + cleaved above heptamer region. - interveing sequences circularise (comp signal ends) + leave. Coding ends (hairpin loops) on segmenets recognised as damaged DNA by ubiquitous repair machinery -> joins DNA together - NHEJ using DNA-PK, XRCC4, LIGIV, Artemis enzymes Lymphoid specific TdT adds in random nucleotides to joined segments.

Answer 88

- RAGs bind + cleave RSSs -> hairpin coding ends - resolution of hairpin -> palindromic P-nucleotides - N-nucleotides added by TdT - pairing of strands + exonuclease cleavage followed by DNA synthesis + ligation -> coding joints Imprecision increases chance of random addition - frameshift/premature stop codon -> non-productive joins

Answer 89

Combinatorial - multiple gene segments, any H w/ any L chain Junctional - P nucleotide & N-nucleotide addition, exonuclease activity - largely localised to CDR3 joins between V(light)/D(heavy) & J

Answer 90

TCR has a & B chain loci - segments also flanked by RSSs recognised by same specific RAG proteins B & T receptors similar gene organisation + same recombination machinery. Gene rearrangement take splace in bone marrow + thymus. - many more J segments in TCRs (13B + 61a) - D segments read in all frames, TdT activity at all junctions -> far greater junctional diversity in TCRs (2x10^11) vs Ig (3x10^7) ## Footnote TCR diversity focused on CDR3 - larger contact to antigenic peptide on MHC

Answer 91

Via series of checkpoints linked to lymphocyte development -> ensures allelic exclusion + clonality

Answer 92

H chain: Early-pro -> D-J rearrangements Late-pro -> V-DJ rearrangement on 1st chrom (can be on 2nd chrom as backup if required - cell lost otherwise) L chain: Pre B-cell -> k gene rearranged on 1st chrom, or 2nd chrom, or delata gene on 1st chrom, or 2nd chrom If kappa rearranged -> u:k IgM expressed If delta rearranged -> u:delta IgM expressed ## Footnote Failed joins are non-productive

Answer 93

Productive H chain (V-DJ) combines w/ surrogate L chain + reaches mem surface (cross-linking of L chain confirms progression). H chains now inaccessible, L chains made accessible

Answer 94

H because TdT mainly active during H chain joning | TdT - Terminal deoxynucleotidyl transferase

Answer 95

Secreted generated by alternative RNA splicing -> becomes soluble Alternative polyA site used altering H-chain C-terminal domain SO Pol-III runs through until stop codon at end of SC domain. Caused by upregulation of CstF64 (binds GU rich sequences) + CstF complex -> selection of proximal polyA site vs distal one | SC is secretory component which pentameric IgM can bind ## Footnote Reversible/regulated

Answer 96

False - IgM & IgD co-expression regulated by alternative RNA splicing -> C-u vs C-delta expression ## Footnote Reversible/regulated

Answer 97

Primary is IgM in bone marrow. Secondary - undergone somatic hyermutation (affinity maturation, mutated V) and class switching (functional skewing, different C) - mutation/selection cycles in germinal centres improve response over time

Answer 98

Dis by Steinman 1973 - best APC for activating/programming naive T cells Have MHC + extra stimulatory signal (CD80, CD86) - long finger like processes (dendrites) - Immature DC migrate from bone marrow via blood to enter tissues - In tissues they sample env + act as sensory for damage or infection - Very motile

Answer 99

Classical/conventional DCs (cDCs) Plasmacytoid DCs Monocyte derived DCs (inflam) Langerhans cells

Answer 100

Tissue resident + have cDC1 & cDC2 subsets Diverse family - CD8a (lymphoid), CD11b (myeloid) & CD103 (enriched in gut)

Answer 101

- Sentinels for viral infections - Secrete large amounts class I interferon - Express intracellular PRR TLR7 and TLR9 (eg viral recognition) - Less effective at priming naïve T cells

Answer 102

- monocyte derived - M-CSF and CCR2 dependent - Variety of roles e.g. supporting effector T cells ## Footnote Inflammatory M-CSF binds receptor called CSF1R, which is a tyrosine kinase that triggers signaling pathways that lead to the growth and differentiation of cells

Answer 103

- In skin - More similar to macrophages but some functional overlap with cDC - Self-renew in tissue

Answer 104

BATF3 or IRF8 dependent - Good cross-presentation to CD8+ T cells - Express CD8aa, DEC-205 or CD103 - Produce more IL-12 than cDC2s - Express toll-like receptors (TLR3) - viral recognition ## Footnote IL-12 heterodimer inducing Th1 deifferentiation & IFNy production

Answer 105

IRF4 dependent - Prime naïve T cells - Associated w/ variety of CD4+ Th cell responses - Express CD11b, DC immunoreceptor (DCIR2), CD301b, CD4 or signal regulatory protein-a (SIRPa) - Difficult to distinguish from MoDCs + other DCs induced during inflammation ## Footnote SIRPa binds CD47 (ubiquitous), DC survival, migration, and phagocytosis.

Answer 106

CD103+ DCs in gut drive tolerance to oral antigens from food + commensal bacteria. - induce Treg generation (anti-inflam) - dependent on TGF-B & retinoic acid (vitA mtabolite)

Answer 107

Immature w/ many dendrites - Ag capture/migration Low CD80/86 expression, but have CCR5+6 chemokines. They endocytose soluble Ags - many endosytic vesicles (MHC-II + lysosomal proteins)

Answer 108

MHC-I: intracellular MHC-II: extracellular

Answer 109

- Receptor mediated - Macro-pinocytosis - Viral infection - Cross-presentation after phagocytic/macropinocytic uptake - Transfer between DCs

Answer 110

Exogenous proteins presented by MHC-I, enabling viral recognition w/o DC infection - Peptides taken up from pathogens, infected dying cells + tumour cells - Taken up via MHC-II then processed to be presented via MHC-I

Answer 111

By PAMPs on pathogens. Receptors include: - Pattern recognition receptors e.g. TLRs - Some phagocytic receptors also activate DCs: ○ DC-SIGN recognise mannose, fucose on pathogens ○ Dectin-1 recognise B1,3 glucans in fungal cell walls ○ Receptors for complement

Answer 112

Licenced by pattern recognition receptors. - TLR7/8 signalling induces CCR7 & enhances antigen processing - CCR7 dircets migration to lymphoid tissues + augments co-stim & MHC mol expression - mature DC in paracortex can then prime naive T cells ## Footnote DAMPs (uric acid) or cytokines can also promote licencing

Answer 113

TLR signalling -> induces CCR7 receptor for CCL21. Mature DCs migrate via lymph to lymphoid tissues: mem folds when in circulation, express lots of stable MHC when in lymph nodes High costim mols (CD80/86), stop taking up antigens (poorly endocytic). - also attract naive T cells (express adhesion mols + secrete CCL18) ## Footnote adapted to talk to T cells

Answer 114

- Present Ag to naïve T-lymphocytes, priming - Activate any antigen specific T cells to divide into effector cells that enter circulation

Answer 115

Different subtypes: cDC1 (IRF8+) - Th1/CD8, cDC2 (IRF4+) - Th2 Maturation factors: PAMPs, peptidoglycan promotes IL-12 (Th1 immunity), histamine promotes Th2 (suppresses IL-12) Accessory cells: ILC2, eosinophils support Th2 (IL-5, IL-13 produced) Cytokines: IL-10 & TGF-B promote treg generation

Answer 116

Th1: type 1 PAMPs -> trigger IFN-y, IFN-a, IL-18, CCR5L - IL-12 + 27 for co-activation T cells Th2: type 2 PAMPs -> histamine, PGEp, TSLP & CCR2L ## Footnote Th1 produce IFN-y & TNF-B Th2 produce IL-4 & IL-5

Answer 117

DCs Macrophages mainly interact w/ already primed effector CD4+ T cells. DCs present processed antigen + drive clonal expansion/differentiation of T cells into effector cells.

Answer 118

Monocytes cultured + differentiate to DCs. DCs cultured ex-vivo with elctroproated tumour lysate proteins OR synthesised peptides. Infusion into individual. ## Footnote Both host + tumour cell dterminants need to be considered -> highly heterogenous

Answer 119

1st gen: immature patient isolated or ex-vivo generated mo-DCs, loaded w/ synthetic antigen/tumour cell lysates - limited success BUT safe e.g. Sipuleucel-T 2nd gen: matured mo-DCs, more refined antigen prep methods, better clinically e.g ACAM2000 Next gen: focus on specifc subsets + naturally occurring DCs -> initial trials safe + more effective

Answer 120

CD28 on T cells. CD80/86 on DCs - presence can be upregulated by pathogen presence

Answer 121

Become anergic - unresponsive to antigen Can be useful mechanism to prevent-self-reactivity.

Answer 122

LFA-1 & ICAM-1 interaction -> weak adhesion between CD4+ T cell & DC, close contact w/ presented antigens If correct antigen found - TCR complex w/ MHC-II -> signalling increases affinity binding of LFA1-ICAM1 interaction (conformational change) If correct antigen not found - tethering not strenghtened, T cell moves to look for DC w/ recognisable antigen

Answer 123

Immunological synapse has specifc conformation. Made up of cluster of mols at T cell/DC interface -> supramolecular activation clusters (SMACs)

Answer 124

Outer ring (pSMAC) - LFA1:ICAM1, larger mols so physically excluded from cSMAC Inner circle (cSMAC) - TCR, CD4+, CD28+, MHC:peptide -> high spatial organisation, mols pulled tighter at specific locations between T cells/DC

Answer 125

TCR no cpaability to sigan downstream SO interacts w/ CD3 complex (w/ intracellular domain/ITAMs) Signals also triggered directly by CD28 co-stimulatory mol. -> activation of PTK cascades + calcium signalling -> alters gene transcription via activation of TFs ## Footnote PTKs - Lck, ZAP-70 Ca2+ signalling - calcineurin (phsophatase) activated -> dephosphorylates NFAT ( nuclear factor of activated T cells), which translocates to the nucleus to regulate gene expression.

Answer 126

Driven into cell cycle -> clonal expansion of Ag specific T cells Also express IL-2R on membranes + secrete IL-2 (GF) - act in autocrine or paracrine manner (drives proliferation) Differentiation into effector cells ## Footnote Within 3-4 days, 10,000-100,000 fold increase in no. antigen specific CD4+ T cells. ALL occurs in lymph nodes or spleen.

Answer 127

Small protein released by cells that has specific effects on interactions between cells, on communications between cells or on the behaviour of cells. - acts on cell receptors - can have systemic effects, but mostly paracrine effect ## Footnote Different combinations in time + space deliver different messages.

Answer 128

Respond intracellular pathogens (viruses + some bacteria) - produce IL-2, IFN-y, lymphotoxin (LT) - activate macrophages, stimulate CD8+ T cells to kill infected cells

Answer 129

Respond extracellular pathogens (helminth parasitic worms) - produce IL-4, 5, 9 & 13 - attract + activate eosinophils/basophils, help promoter tissue repair

Answer 130

3rd signal - provided by cytokines Signal 3 for Th1 cells: IL-12 from DCs or IFN-gamma from Th1 Signal 3 for Th2 cells: only needs IL-4

Answer 131

Th1 & Th2 cross-regulate each other. - Th1 downregulates Th2 by IFN-gamma secretion - Th2 downregulates Th1 by IL-4 secretion Responses become polarised towards dominant response - specialised to pathogen

Answer 132

Th17 cells T-follicular helper cells (Tfh) Tregs - reguatory subset

Answer 133

TGF-B IL-6 IL-1

Answer 134

IL-17, 21 & 22 Immune responses at epithelial surfaces at lung + intestine - important for fungal/bacterial infections

Answer 135

Specialised to go to B cell follicles (germinal centres) of lymph nodes to help B cells make antibody via cytokine production. Acquire special receptor (CXCR5) on surface to move there

Answer 136

Select against potentially self-harmful T cells in thymus. Subset of high affinity T cells differentiate to Treg phenotype instead of deletion. - produce reg cytokines to switch off self-reactive T cells -> IL-10, TGFβ, and IL-35 (immunomodulatory) ## Footnote supress self-harmful immune responses, autoimmune patients often have dysfunctional Tregs

Answer 137

CD25 Foxp3 also identified as critical Treg gene - key determinant of autoimmunity.

Answer 138

Produced in thymus as normal part of T cell development OR Made in peripheral tissues/organs - induced by IL-2/TGF-B 3rd signal -> induced/peripheral Tregs

Answer 139

TGF-B & IL-10 suppress immune cell expression. Tregs also for: - Anti-inflam cytokines - Outcompete effector T cells for resources - Kill self-reactive T-cells

Answer 140

Autoimmune disease - Foxp3- mutant in mice -> scurfy animals dont grow In humans -> IPEX, X-linked only in boys, many autoimmune diseases associated

Answer 141

CD4+ subsets able to become other subsets - not solely one-way traffic.

Answer 142

Macrophages + neutrophils: kill pathogen Dendritic cells: present pathogen ## Footnote Macrophages can act as APC later in immune repsonse

Answer 143

Mast cells, eosinophils, basophils & neutrophils ## Footnote Many innate immune cells ativated by PRRs e.g. TLRs

Answer 144

Reside in tissue, produced from either monocytes from bone marrow (enter tissue from circulation) or embryonic cells during development. - sense/move towards pathogens via chemotaxis - phagocytic receptors on membrane

Answer 145

CCL8, 9 + 21 receptors mediate M1 chemotaxis CCL7 receptors mediate both M1 & M2 chemotaxis -> polarisation of macrophage responses

Answer 146

90% circulating granulocytes, readily activated, move into sites of inflammation. Short life - pus = dead neutrophils, highly phagocytic. - sense + move towards pathogens via chemotaxis (CXCL8-R)

Answer 147

Pathogen engulfed into phagosome -> acidified (mediated by V-ATPase proton pumps) Fuses w/ lysosome forming phagolysosome (has enzymes, toxic oxygen species) In neutrophils, cytoplasmic granules & anti-microbial peptides fuse with pahgosome

Answer 148

Cathelicidin LL-37

Answer 149

Make up 2-5% blood - rare Toxic granules: eosinophil cationic protein, major basic protein Can be activated to degranulate by - complement, Ab, cytokines

Answer 150

Make up 0.2% blood - rare Toxic granules: histamine, prostaglandins (PGD2), heparin, leukotrienes Can be activated to degranulate by - complement, Ab, cytokines ## Footnote PGD2 - suppress IL-12 production, induce Th2 response ALSO chemotaxis & histamine release

Answer 151

Basophil-like but found in tissue (not blood). Bind IgE (bound to FceRI) on cell surface w/ high affinity at rest. Mast cell activated when IgE binds antigen (multivalent) -> release granules

Answer 152

Innate cells that produce cytotoxic molecules to kill 'altered' cells -> infected/tumour cells Express activating and inhibitory receptors (inhib-R binds MHC-I) If cell is infected/cancerous -> downregulates MHC-I for NK cell inhib receptors SO NK cells kill abnormal cells

Answer 153

True - increases ability to fight complicated infections + acts as fail-safe Innate + adaptive immunity exhibit significant cross-regulation/communication largely via cytokine/Ab production

Answer 154

Major innate immune system - provides early killing of pathogens. Has > 30 different soluble proteins, made in liver as inactive precursors + present in blood & other bodily fluids in inactive form.

Answer 155

Cleaved into 2 or more parts - activated Smaller fragment may mediate inflam. Larger fragment has 2 sites -> active site & binding site for next protein cascade

Answer 156

Classical Alternative Lectin All generate C3 convertase, which cleaves C3 -> C3b bound to microbial surface + C3a released

Answer 157

C1q binds to one pentameric IgM mol in staple form on bacterial surface OR C1q binds at least 2 Ag-bound IgG mols C1q binding to Ig activates C1r -> cleaves & activates serine protease C1s ## Footnote Ab-dependent

Answer 158

Cleaves C4 to C4a & C4b (binds microbe) C4b2a is active C3 convertase So cleaves C3 to C3a + C3b which bind to microbe or to convertase itself

Answer 159

Opsonin - marks pathogens/immune complexes for phagocytosis Downstream also forms C5 covertase complex (C4b2a3b) -> membrane attack complex (MAC) formation ## Footnote MAC is pore forming protein complex

Answer 160

Complement binds pathgen surfaces + involves complement factors B & D. C3 spontaneously hydrolysed -> C3(H2O), can bind factor B, then cleaved by D into Ba & Bb C3(H2O)Bb complex is C3 convertase, C3 cleaved -> C3a + C3b ## Footnote Ab dependent

Answer 161

Complement binds mannose binding protein - bound to pathgen surface. Mannose binding lectin (MBL) & ficolins bind to pathogen glycoprotein polysaccarides on surface. -> triggers activation of MBL-asscoiated serine proteases (MASPs) which bind MBL MBL-MASP complex cleaves C4 & C2 -> C3 activation ## Footnote Ab independent

Answer 162

1. Induction of lysis 2. Opsonisation of pathogen 3. Induction of chemotaxis & inflammation 4. Immune complex clearance (small Ab-soluble antigen complexes, not enough Ab to mediate phagocytosis)

Answer 163

Cytokine production

Answer 164

Normally against intracellular pathogens. Central activators of macrophages via IFN-gamma secretion & CD40 ligand-CD40 interaction. - activated macrophages upregulate MHC-II (more T cell activation) ## Footnote Takes time - prolonged attachment of Th1 to macrophage -> delayed type hypersensitivity (DTH)

Answer 165

- induce macrophage differentiation in the bone marrow via IL-3 & GM-CSF - Induce T-cell proliferation, increase numbers of effector cells via IL-2 - Kills chronically infected cells releasing bacteria to be destroyed via Fas ligand & IFN/TNF

Answer 166

Deal w/ large extracellular pathogens (worms) Can help B cells produce Ab via IL-4 (B cell GF), also function of Tfh. Activate basophils, eosinophils + mast cells via IL-4, 5 & 13

Answer 167

Can activate 'alternatively activated' M2 macrophages via IL-4 + 13. These macrophages -> TGF-B + RELM-a, promotes wound healing ## Footnote RELM-a activates fibroblasts to upregulate lysyl hydroxylase 2 -> boost collagen cross linking

Answer 168

Regulate responses against extracellular bacteria + fungi. Produce IL-17 & IL-22: IL-17: act on many cells to induce cytokine/chemokine secretion, neutrophil recruitment, stimulate neut + macroph production in bone marrow IL-22: antimicrobial peptide production e.g. Reg3 family AMPS, lipocalin-2 (sequesters iron to reduce bacterial growth)

Answer 169

MHC-I activated to form CTLs - directly kills. Proliferate/differentiate via IL-2 secretion + autocrine signalling w/ IL-2R After activation, CTLs do not require co-stimulation to kill cells via cytotoxic granule release.

Answer 170

- binds target losely - recognises antigen (via MHC-I) & Tc cytoskeleton reorganises, granules moved to contact site - cytotoxic granules released at cell-cell contact (specific killing)

Answer 171

Granzymes - serine proteases that induce apoptosis Granulysin - antimicrobial + induces apoptosis Perforin - helps deliver granule contents to target cell by pore formation in cell membrane Directed granule secretion prevent viral spread to other healthy cells.

Answer 172

Yes. - IFN-gamma to activate macrophages, increase MHC-I expression in infected cells (pos feedback) & directly inhibit viral replication - TNF-a/LT-a helps IFN-gamma activate macrophages, helps directly kill infected cells

Answer 173

Both activate macrophages via IFN-gamma. CTL directly kills infected macrophages. Th1 differentiation increased via IFN-gamma. Also stimulates T cell proliferation (-> CTLs) via IL-2 secretion.

Answer 174

Not directly toxic, but facilitate immune mechanisms. Neutralisation Agglutiniation Opsonisation ADCC Classical complement activation Specialised responses

Answer 175

Clumping of particles -> latice work more likely to be phagocytosed Can involve complement (removing immune complexes)

Answer 176

Complement & IgG coat bacterium. C3b binds CR1 on macrophage & conserved IgG region binds Fc receptor -> phagocytosis

Answer 177

Ab binds infected cell or large extracellular pathogen Ab makes bridge to immune cells via FcR + mediates death via degranulation/innate directed killing

Answer 178

IgE-mediated activation of mast cells -> degranulation SO lipid mediators, cytokines, granules (e.g. histamine) are released Initiates inflammatory response (increased vasodilation, increased vascular permeability ->accumulation of immune cells at site of infection)

Answer 179

Monoclonal antibodies are produced by a single B cell clone and bind to a single epitope on an antigen, offering high specificity and consistency. Polyclonal antibodies, on the other hand, are produced by multiple B cell clones and bind to multiple epitopes on the same antigen, providing broader recognition and sensitivity

Answer 180

Antigen samples injected, immuised many times over 10 weeks -> maximise class switching + selection Serum enriched for specifc Abs against injected antigen. - used for diptheria 'anti-toxin' 1890 - convalescent plasms confers passive immunity to recipients (high Ab levels)

Answer 181

Used to make mAb. Has Ab producing gene from B cell fused w/ myeloma that has immortal + highly proliferative properties.

Answer 182

Mouse immunised repeatedly w/ antigen -> class switching + increase affinity. Spleen cells removed containing antigen-specific B cells (splenocytes) - isolated. - splenocytes fused in vitro w/ myeloma - myeloma has purine enzyme deficiency + cannot secrete Ig - cells cultured in HAT medium, only fused cells that can utilise purine survive Then plated so 1 hybridoma per well. Hybridoma Abs screened agaisbt orignal antigen + clones selected -> immortal lines secreting mAbs | HAT - hypoxanthine, aminopterin & thymidine

Answer 183

- High specificity - Low cross-reactivity - Standardised worldwide - Unlimited supply - Many different uses i.e. immunoassays, diagnosis, tissue typing

Answer 184

In vivo - trigger immune response but not access sites needed -> off-target effect SO can create Fab fragment delivery system using insects to circumvent immunity.

Answer 185

- affinity chromatography - immunoisolation (magnetic separation) - (haem)agglutination - ELISA/ELISpot - Immunohistochemistry/fluorescence - Western blotting - Flow cytometry

Answer 186

mAb bound to beads used to purify Ag from a mixture of molecules Unbound mols washed away + purified antigen eluted

Answer 187

Obtains purified cell populations, can be sed clinically. mAbs coupled to paramagnetic beads + poured over iron wool mesh -> magnetic field applied Cells specific to Ab stick to mesh + othrs washed out

Answer 188

Identify if Ab present for an Ag + visualise clumping as complexes form - used in blood typing + test if patirnt had infection (serums mixed w/ pathogen culture Haemagglutination to test for blood type: A has anti-B Abs, B has anti-A Abs. Abs colourless so need fluorescnet markers (FITC), metal ions or enzymes markers (peroxidase)

Answer 189

Used clinically for viral diagnostics, hormone levels etc. mAb added, covalently linked to enzyme. Susbtrate added which binds enzyme to induce colour change. - measure using absorbance Secondary Ab can be used for increases sensitivity - ammplifies signal

Answer 190

Highly sensitive assay - measure freq of cytokine/Ab secreting cells at single cell level. Cells cultured on +/- stimuli w/ capture mAb, cells removed but Ab remains on plate - secreted Ab then visualised using substrate reaction: - detection mAb-biotin added w/ streptavidin enzyme + ALP for precipitation | ALP - alkaline phosphatase

Answer 191

Shows localisation for Ag - can be quantitative. Needs fresh, frozen, fixed tissues. - useful for DNA seqs on chroms, spatial/temporal patterning of gene expression Histochemistry - uses enzyme substrate reactions -> anti-glucagon & anti-insulin Abs

Answer 192

Qualitative + quantitative analysis of protein expression -> tissue homogenates or cultured cells. Can be used diagnostically (Lyme disease, HIV) SDS-PAGE before transfer over to nitrocellulose membrane w/ antiserum. Enzyme linked anti-IgG used to detect bound Ab (secondary)

Answer 193

Abs against different cell durface proteins - lasers detect fluorescent Abs bound to cells. -> qualitative & qunatitative info : level of activation, cell viability, cytokine secretion, rare cell types Used clinically - tumour detection, monitoing cell number ## Footnote produces scatter plots

Answer 194

TNF therapy - mAbs for TNF-a used for RA, IBD, psoriasis & ankylosing spondylitis Can also be used to enhance T cell responses by blockaing immune checkpoints. - anti-PD1 & anti-CTLA-4 Abs -> Can boost immune responses to tumours

Answer 195

Primary adaptive response to infection often slow & weak -> protective immunity Secondary exposure induces greater, more rapid response w/ higher affinity. -> memory

Answer 196

- Expansion of 'clones' of cells w/ re-arranged antigen receptor genes specific for primary antigen encountered * TCR * BCR/Ig - Enhanced migration & re-stimulation properties: adhesion mols, rapid effector function - Survival: maintenance of clones, responsive to growth/cytokine survival signals

Answer 197

Ag specific, already undergone class switiching + affinity mat. Can re-enter germinal centres in secondary response -> somatic hypermutation + affinity mat BUT needs CD4+ Th cell help for Ab secretion (not a plasma cell)

Answer 198

IL-7 & IL-15 -> homeostatic proliferation

Answer 199

- Express high cytokine levels - IL7R for survival & genes like bcl2 - High adhesion molecules - Lower expression markers associated w/ effector cells e.g. CD69 Can be tissue resident or adapted for recirculation through lymphoid (central) or adapted to rapidly re-enter inflamed tissues (effector)

Answer 200

- mem also have IgG, IgA & IgE - mem have high Ig complement receptor - mem in bone marrow, lymph node + spleen but naive only in spleen - both recirculate - mem higher affinity - mem higher ICAM-1 expression

Answer 201

Variolation portected against smallpox in 1500s - in UK 1717 by Lady Montagu BUT 1% death rate Jenner 1796 1st small pox vaccine from cowpox (innoculation) Pasteur vaccines for rabies + anthrax (1879), based on weakened pathogen forms

Answer 202

Generate protective antibodies & inducing T cell & B cell memory. Requires Ags from targte pathogen & infection signal (alert immune system) - Live & attenuated naturally provide both - Other vaccines provide antigens but need adjuvant to provide infection signal - Some need boosters

Answer 203

Live attenuated Killed/inactivated Portein subunit Recombinant viral-vectored Virus like Nucleic acid based (mRNA)

Answer 204

Related, less harmful infection: * Vaccinia (cowpox) related to Variola (smallpox) * BCG bacteria (bovine tuberculosis) related to Mycobacterium tb. * Highly effective, rarely found in nature, dangerous to immuno-compromised patients. Live attenuated pathogen: * Sabin oral Polio, MMR, chickenpox * Highly effective, some risk of disease in immuno- compromised patients

Answer 205

* Salk Polio virus * Lower risk of disease but can occur due to improper activation * May need boosters * Inactivated using heat, chemicals (formaldehyde), radiation to preserve antigen structure but stop pathogen replication

Answer 206

* Use antigens that best stimulate the immune system e.g. Hepatitis B, Novavax vaccine for SARsCOV-2 * May be linked to e.g. boosting mechanism such as a bacterial stimuli e.g. HiB meningitis

Answer 207

* Virus bioengineered to express target pathogen in vivo * Widely investigated w/ good safety e.g. Ebola * Often use non-human virus carrier e.g. simian adenovirus used for AZ SarsCov2 vaccine If use same carrier repeatedly -> causes reactivity to carrier virus

Answer 208

* Highly effective, closely resembles live virus but non-infectious * Can have multiple antigenic components e.g. Gardasil for Human Papilloma Virus

Answer 209

* Can encode many antigens (even whole genome) * Antigen encoding mRNA complexed w/ a carrier like lipid nanoparticles to be delivered into target cells * Antigen transiently expressed by target cells -> immune response * Non-infectious & quick to manufacture, can be tricky to store as requires cold chain to store e.g. SarsCov2 Moderna & Pfizer

Answer 210

Chemicals that boost immune response to an Ag - stimulate inflam + T cell activation via APC e.g. oil/water emulsion, alum, TLR ligands, liposomes

Answer 211

Individual MHC type -> not all Ag immunogenic in everyone + some pathogens mutate rapidly (many life cycles) SO multivalent vaccines deliver variety of Ag epitopes w/ adjuvant -> ranging immune response

Answer 212

Delivered via nose/throat (inhalable/sniffable) More tissue specific - can block respiratory viruses + potentially more durable Used for flu + investigated for COVID-19 ## Footnote e.g. Fluenz Tetra/FluMist

Answer 213

- Complicated pathogen life cycles - malria has stage specific immune responses - Antigen variability - Latency (HIV/Herpes viridae) e.g. no vaccine for HIV + TB (1/4 global pop infected) Also lack of research into torpical zoonotic infections e.g. Zika, Ebola, COVID-19

Answer 214

Socioeconomic factors - education, beliefs Social influences - professional recommendations, social media, previous experiences Trust - efficacy & safety of vaccine, misinformation Accessibility - cost, convenience, availability, language barriers

Answer 215

Control: the idea that we can take back control of our own bodies through alternative means. Parenting style: philosophies that shun mainstream medicine, opting for “natural” remedies. The Past: previous bad healthcare experiences or a bad experience around vaccination shapes perceptions. Risk: misunderstandings about the risks of vaccination versus the risks of disease. Fear of chemicals: the fear that the vaccine will introduce toxic chemicals. Distrust of government agencies and corporations.

Answer 216

Certain prop must be immune to protect the rest of the population from a pathogen - depends on virulence of pathogen + pop susceptibility e.g. measles needs ~90% (very virulent)

Answer 217

Wakefield 1998 linked it to autism -> fraudulent + unethical, no replicative study Measles rose in Europe 30-fold

Answer 218

Misinformation is false or inaccurate information—getting the facts wrong. Disinformation is false information which is deliberately intended to mislead—intentionally making the misstating facts - can be very lucrative Algorithms fuel spread of disinformation further ## Footnote Disinformation dozen: 12 people responsible for almost 2/3 of anti-vaccine content circulating on social media platforms

Answer 219

Immune system needs broad recognition whilst avoiding self-harm. Self-reactivity normal in healthy immune system BUT restrained by tolerance mechanisms. Tolerance is antigen specific. 1. limit production of self-reactive T & B cell clones 2. prevent unwanted destructive responses by any clones produced

Answer 220

Failure to respond to intrinsic self-antigens Acquired, not inherited. - Non-identical twin calves sharing common placenta become tolerant of each other - chimerism of blood systems (shared components) - Tolerance may be induced to antigens that are shared as a foetus (able to tolerate skin grafts from each other)

Answer 221

Yes - harmless non-self Ags (commensal bacteria & fetomaternal antigens) - therepeutically relevant Ags e.g. allergens, transplantation

Answer 222

NO - protection form autoimmunity is compromise: Removal of dangerous self-reactivity WITHOUT impairing capacity for broad recognition & effective defence. Mechanisms inc: - inactivation of ptoentially self-reactive clones - immune regulation - self-epitopes not available for recognition

Answer 223

Central - in primary lymphoid organs (bm, thymus), self-reactive lymphocytes removed during development - not absolute Peripheral - in peripheral organs/tissues & secondary lymphoid organs, many mechanisms to limit self-reactivity

Answer 224

Checks ORFs created to make H chain that will fold w/ L chain to form surface receptor (BCR) - monitors VDJ rearrangement If successful, signals cell to downregulate Rag enzymes for recombination -> proliferation before rag genes turned back on ## Footnote Ag independent

Answer 225

Checks self-reactivity of receptor after VJ rearranging of L chain. IgM now expressed on cell surface B cell fate determined by interaction w/ self-antigen in bone marrow - influenced by conc of antigen & ability to cross-link surface receptors. If self-reactivity dangerous -> clonal deletion OR receptor editing ## Footnote Ag dependent

Answer 226

Repeated VJ rearrangements at L chain foci. If 1st recombination fails, nonproductive join: - rag genes stay on + rearrange again Generates non-autoreactive mature B cell + exits to periphery OR clonal deletion

Answer 227

Non-self reactive -> mature B cell migrates to periphery. Self-reactive clones -> deleted or rescued via receptor editing Self-reactive clones w/ low affinity (non-cross linking) slef mol -> ignorant clones to periphery, cannot bind Ag in enough conc, insufficent context to cause activation Self-reactive clones w/ soluble self-mol - anergic clones to periphery, functionally unrespnsive to Ag stimulation

Answer 228

Lymphoid progenitor ibteracts w/ stroma -> commits to T cell (95% become aB T cells) early thymocyte -> double negative thym (DN) -> double positive thyms (DP) -> single positive thyms (SP) VDJ(beta) recombination at DN stages VJ(alpha) recombination at DP stages ## Footnote Stepwise process DP has both CD4+ & CD8+

Answer 229

Checkpoints remove useless/harmful clones: - fail to express TCR - cannot recognise self-MHC mols - recognises self-MHC:self-Ag too strongly ## Footnote Only ~2% of cells that make TCR make it through thymic selection to enter periphery

Answer 230

Has TCR-B gene rearrangement -> functional pre-TCR expression Quality check to see if B-chain can bind to surrogate a-chain + make pre-TCR. - survival signal downregulates Rag - proliferation before a-chain rearrangement Otherwise apoptosed ## Footnote Occurs DN3, Ag independent

Answer 231

Positive selection - can rearranged alpha-beta TCR recognise self-MHC:self-Ag? 10-30% of new TCRs survive + move to medulla regionas SP T cells. IF TCR cannot recognise - rag genes left on + receptor editing of a-chain OR apoptosed ## Footnote Occurs at DP stage.

Answer 232

Negative selection - does alpha beta TCR recognise self-MHC + self-peptide too strongly? DCs + medullary ep cells present Ag to SP thymocytes. Medullary ep cells express AIRE & Fezf2 (transcription regulators) -> allow promiscuous gene expression -> gene mosaicism, provides non-thymus peptides for neg. selection Macrophages clear up dead thymocytes in development.

Answer 233

Binding affinity. TCR binding not too strong - T cells survive TCR binding moderate/strong - thymic Tregs (Foxp3+) - useful T cells exit thymus Non-function or overly strong binding -> apoptosis

Answer 234

Lack of T cell help B cell not activated by Ag so does not differentate to plasma cells In germinal centres: B cell competes w/ follicular DC for Ag. - Ag presentation by DC in absence of danger is tolerogenic (anergic)

Answer 235

T cells receive signal 1 alone -> is unresponsive to Ag e.g. when encountered in absence of danger

Answer 236

Driven by presence of Ag & immune suppressive signal 3: Ag + TGF-B -> pTreg (Foxp3+) Ag + IL-10) -> Tr1 (Foxp3-) ## Footnote Immunosuppressive cytokines

Answer 237

tTregs recognise self Ag pTregs recognise self Ag + harmless non-self Ag -> allow temperance of immune responses to harmless non-self Ag (microbiome commensal bacteria/food)

Answer 238

- Production of anti-inflammatory, pro-regulatory cytokines; TGFβ, IL10, IL35 (dependent on signals driving differentiation of the Treg) - Modulation of dendritic cells - Outcompete effector T cells for resources; IL2 (Treg commonly express IL2R) - Direct killing of T cells - Exosome transfer of miRNAs

Answer 239

NO - gut exposed to many non-self antigens so more tolerogenic.

Answer 240

Allows desensitisation to an antigen via exposure to high tolerance in the gut e.g. ingested poison ivy reduces allergic skin reaction following contact

Answer 241

Antigens in immune privilege sites do not induce immune attack - brain, eye, testis, uterus, hamster cheek pouch - Enclosed by physical barrier - Low MHC-I - Rich in suppressive cytokines (TGF-B) - Express FasL Grafts placed in these sites not rejected - antigens placed at these sites don’t elicit destructive immune response.

Answer 242

Immune privilege broken. Trauam at 1 eye -> intraocular Ag acrried to lymph + activate T cells BUT effector T cells return via blood to encounter Ag at BOTH eyes.

Answer 243

Low immunogenicity Tumour treated as self-Ag Antigenic modulation Tumour induced immune suppression - induce Tregs via cytokine secretion Tumour induced privilege sites (TME) Hampers treatments - immunotherpies need to overcome suppression.

Answer 244

Immune response againts one or more self-antigens

Answer 245

Caused by autoimmune response & develops due to failure of self-tolerance. Normal effector mechanisms triggered. - Usually not possible to clear self-antigen -> chronic response 5-8% of pop, >80 different diseases - RA most common

Answer 246

AIRE mutants - expression helps screen for storngly reactive T cells Mutations in Foxp3 - linked to IPEX, involved in Tregs development ## Footnote IPEX - immunological polyendocrinopathy X-linked disease

Answer 247

Defects in FoxP3 gene (Tregs) -> immunodysregulation, polyendrocrinopathy, enteropathy. - Systemic autoimmunity, begins 1st year life -> diarrhoea, endocrinopathy (diabetes) + eczema Treatments: bone marrow transplant & immunosuppressive agents.

Answer 248

Organ-specific: effector function againts Ag confined to affected organ - MS, myelin sheath targeted on CNS axons - Type 1 diabetes, B-cells of pancreas targeted Systemic: widespread Ag found in most cells - Systemic Lupus Erythematosis (SLE), anti-nuclear antigens (ANA) - RA ## Footnote Can get more than 1 autoimmune condition e.g. autoimmune haemolytic anaemia can be on its own or in combo w/ SLE

Answer 249

1o - direct consequence of autoimmune response 2o - consequence of primary pathology (symptoms) e.g. Hashimoto's thyroiditis primary - destruction of thyroid tissue secondary - hypothyroidsim due to loss of thyroid

Answer 250

Auto-Abs depositied in tissues + formal immune complexes Cellular infiltrate (B & T cells) -> autoreactive CD4+ Th cells involved in ~all autoimmune diseases - support B cell stim to make Ab, amplify macrophage responses, target killing via Tc cells, cytokine production Th17 cells also implicated

Answer 251

Th1 & Th17 specific for myelin basic protein. ## Footnote EAE -Experimental Autoimmune Encephalomyelitis

Answer 252

Damage or destruction - complement & opsonisation Alteration of function - stimulation, inhibition/blockage of function Deposition of immune complexes

Answer 253

Can be via: - Complement mediated lysis, MAC lyses rbc -> autoimmune haemolytic anaemia - opsonisation of platelets -> autoimmune thrombocytopenia (bleeding)

Answer 254

Stimulation: auto-Ab agonist activity at TSH receptor - stimulates hormone production -> short-circuits negative feedback regulation mechanism - Graves disease (hyper-thyroidism) Inhibition: auto-Ab antagonist at receptor -> causes internalisation + degradation of endplate - Myasthenia Gravis Blocking: auto-Ab binds intrinsic factor, so it cannot bind + absorb VitB12 -> lack of rbc + tiredness - pernicious anaemia

Answer 255

In SLE, complexes deposit in small blood vessel walls -> inflam reaction - Arthritis, 'butterfly rash', vasculitis, glomerulonephritis - Very rare

Answer 256

Yes - genetic concordance of related individuals. In autoimmunity concordance in identical twins is larger than non-identical twins BUT <50% -> large environmental role

Answer 257

- Structural polymorphism: different forms of protein made (coding region of gene) e.g. MHC - Non-structural polymorphism: altered protein activity/protein levels (if in non-coding region promoter/enhancer) Expression of polymorphic alleles -> autoimmunity NOT mutations

Answer 258

Degree an allele of a gene increases susceptibility e.g. HLA-DRB1 gene is strong risk factor for RA Complex multi-gene interactions increase genetic risk

Answer 259

75% autoimmune diseases found in females, arises child-bearing years Ankylosing Spondylitis is one of few diseases more common in males.

Answer 260

- vitD, active form may suppress Th17 development - Drugs/metabolites can bind self-Ag + so Ag appears foreign - Toxins cause damage + expose areas for auto-Ab mediated damage - Microbiota/hygiene -> specific commensal (lack of) bacteria - Pathogens can resemble self-antigens + interact w/ risk genes

Answer 261

EBV nuclear antigen 2 is TF that interacts w/ several genetic risk loci associated w/ lupus - also T1DM, RA & MS NK cells & specific CD8+ T cells associated w/ raised MS risk

Answer 262

B cell mitogens can stimulate auto-Ab production in absence of Th cells e.g. bacterial LPS -> plasma cell differentiation. - Not Ag-specific - LPS is acting mitogen - Usually transient

Answer 263

Molecular mimicry between pathogens + self-Ag Rheumatic fever - streptococcal cell wall M-antigen stimulates Abs, can also react to heart myosin, joints & kidney.

Answer 264

Binds self-antigen, modifying it to created T cell epitope that appears foreign, enabling T cells to help autoreactive B cells Normally finite but genetic predisposition can trigger Th cells for self-Ag -> chronic autoimmunity

Answer 265

Via positive feedback from inflammation -> inability to clear antigen. Broadening immune response - epitope spreading (hidden/cryptic epitopes revealed)

Answer 266

Allergy - excessive immune response to harmless antigen, usually specific + restricted. Systemic responses can result in death via anaphylaxis ## Footnote ~20-25% UK population

Answer 267

Type 1 airway hypersensitivity -> lung epithelium inflammation, smooth muscle contraction, mucus production - IgE mediated, severe bronchiole constriction

Answer 268

- Sensitisation of Ag specific IgE - Re-exposure & activation of inflam response

Answer 269

1. exposure to allergen -> stimulation of Th2 cells, make IL-4 + help produce IgE Ab 2. B cells produce IgE that recognises allergen 3. IgE circulates in blood + associates w/ mast cells in mucosal & connective tissues via FcεR - receptor to constant region of IgE

Answer 270

- Allergen binds IgE on mast cells -> release inflammatory mediators when IgE /FcεR cross-linked by allergen binding - Mast cells release histamine, cytokines, prostaglandins + leukotrienes - Causes vascular permeability, inflammation, muscle contraction, mucus production, immune cell recruitment, swelling, redness, blistering, itching

Answer 271

Mast cells - release granules w/ histamine etc. Eosinophils (dominant allergy ft) also have FceR + can release IL-4 - need IL-5 for their development

Answer 272

GI tract - increased fluid secretion, expulsion of content Airways - decreased diamater + increased mucus production -> congestion + breathlessness, swelling Blood vessels - increased flow + permeability -> increased effector response in tissues (inflam)

Answer 273

Systemic response to an allergen -> triggered by large release of histamine. - Dilation of local blood vessels -> drop in blood pressure + consciousness - Difficulty breathing as airways narrow - Oedema or swelling into surrounding tissue ## Footnote Fatal if not dealt with

Answer 274

Rarer than other type 1 insensitivities, approx 1/50 children. 46% anaphylaxis deaths '92 ->2018 from peanut/mut allergies - reduced when introduced to infants diets at 4 months

Answer 275

IgG mediated, react to antigens on cells or tissues

Answer 276

Blood transfusion reactions: IgM binds transfused RBC (complement) -> fever, chills, vomiting Haemolytic disease of newborn: Rh- mum + Rh+ partner, baby + mum blood can mix -> sensitisation Prevented w/ anti-Rh Ag antibodies to bind any free foetal RBCs + destroy them before sensitisation. Haemolytic anaemia ## Footnote Can also be drug induced

Answer 277

IgG mediated, against soluble Ag in immune complex w/ Ab. Local - repeated inhalation of antigen e.g. Pigeon Fancier's disease (dried faecal antigens), Farmer's lung (mould spores in hay) Systemic - infection e.g. malaria or in response to serum administration (serum sickness), SLE

Answer 278

Systemic type 3 insensitivity. Animals serum stimulates Ab response (2 doses), Ab to serum proteins form complexes -> deposited in blood vessels, can cause fever, rash, arthritis, kidney disorder.

Answer 279

Contact, allergic reaction after skin contact w/ allergen. Cell mediated - no Ab, instead has Th, Tc + macrophages Takes 24-72hrs -> swelling, blistering + itching e.g. poison ivy, nickel, hapsten responses

Answer 280

Skin prick - lancet introduces allergen to epidermis -> wheal + flare reaction within mins, late phase reaction 4-6 hrs IgE presence using ELISA - if +ve, person atopic (predisposed) to allergy, may be no clinical symptoms Patch tests - allergens applied topically & left for 24-72 hrs to assess type 4 hypersensitivity

Answer 281

YES - likelihood increases w/ 2 atopic parents, concordance of atopy is 60% in identical twins (env also has role) MHC e.g. HLA-DR5 associated w/ birch pollen, non-MHC-genes (IL-4, FcεR ) epithelial barrier function.

Answer 282

Prevalence of allergy + asthma has increased dramatically over last 50 yrs - less exposure to antigens when children. Contributed by increasing Th2 polarising substances, pollutants, urbanisation, hygiene? -> exposome.

Answer 283

1989, Strachen Children raised in large families in country less likely to have allergy/autoimmune disease. - Exposure to environmental microbes when young may help prevent hypersensitivities.

Answer 284

Evolved from hygiene hypothesis. - Reduced microbial diversity in our microbiome due to wester diets + urbanisation - Reduction in worm infections Babies given antibiotics early on -> more likely to develop allergies (altered microbiome). Low asthma prevalence in pops exposed to high microbial environment. Link between eosinophils in asthma due to altered exposure of short chain fatty acids derived from microbiome.

Answer 285

Th2 & IgE responses deal with parasitic worms, so evolved to deal with them. Deworming campaign in Kenya - increased eczema in dewormed children (atopic dermatitis) - may play role in allergy mediation

Answer 286

- correlation of higher incidences of allergy where lower parasite infections - european divide: more allergic diseases in indutrialised countries (Sweden) vs rural countries (estonia) - rural vs urban epidemiological studies

Answer 287

- South/latin america has more asthma than spain/portugal depsite similar culture + poorer living conditions (but high pollution) - worm infections common in parts of USA - asthma increasing in African countries in poverty - industrialised nations not that clean -> pollutants of air + water ## Footnote Also dependent on climate changes -> pollen

Answer 288

- Anti-histamines - Steroid anti-inflam drugs - Adrenaline/epinephrine (Epi-Pen) - vasoconstriction blood vessels

Answer 289

Desensitisation - intra-muscular injection of low dose allergen, monthly 2-5 yrs -> raise IgG rather than IgE

Answer 290

Duplimab blocks cytokine (IL-4) that promotes Th2 differentiation Benralizumab targets IL-5R prevent eosinophil/basophile development + survival

Answer 291

Exposure to antigens leads to T cell tolerance, low doses ingested antigen can re-train immune system (high tolerance of gut) e.g. Palforzia (AR101) - peanut derived protein used to redirect immune response

Answer 292

Eosinophilic inflam - anti-IL-5/R, anti-IgE, anti-IL-13, anti-DP2 T1/T17 neutrophilic inflam - anti-IL23, anti-IL17, anti-CXCR2

Answer 293

Worms have evolved to redirect our immune response so could they dampen inappropriate responses Human trials - hookworm infection to treat asthma, investigated for coeliac disease May simply be able to purify parasitic products and use to modulate immune response.

Answer 294

Allows varied selection criteria at different checkpoints during tolerance generation. Quality check (DN3) - subcapsualr region Positive selection (DP) - cortex Negative selection (SP) - in medulla (has med ep cells)

Answer 295

Antibody-dependent cellular cytotoxicity (ADCC) Antibody-dependent cellular phagocytosis (ADCP) Complement-dependent cytotoxicity (CDC)

Answer 296

All bind IgG1 w/ highest affinity. I - resp burst + reactive O2 species, release cytotoxic granules II - eosinophil granule release, B2 -> phagocytosis, both Bs have immunomodulatory tyrosine inhibitory motifs (ITIMs) III - recruits NK cells via intracellular signalling through y or c domain ## Footnote Most common

Answer 297

IgG transport + recycling to extend of its half life. Binds IgG Abs + serum albumin w/ high affinity at low pH - recycles IgG -> enhance mAb drug efficacy

Answer 298

- Effector cells are all leukocytes which express Fc receptors and contain cytotoxic granules - Three types of Fc gamma receptor are involved: FcγRI, FcγRII + FcγRIIIA - Mechanisms of killing include release of cytotoxic granules containing granzyme and perforin, and generation of reactive oxygen species (ROS) to induce apoptosis of the target cell

Answer 299

Clearance of pathogens via pahgocytosis. Ab binds activating FcyRs on phagocytes -> actin cytoskeleton remodelling - forms phagosome -> pro-inflam cytokine/chemokine release

Answer 300

Reduce effector functions of mAb treatments induced by Fc receptor interaction. Aglycosylation - removes N-linked glycan (N297) which normally binds FcyR + activates complement Fucosylation - fucose added -> steric hindrance preventing IgG binding FcyRIIIA, sailic acid addition also reduces binding affinity -> prevents ADCC + CDC

Answer 301

Fusion protein to treat RA. Fucosylation. -> highly sialylated IgG mediates immunosuppressie efefcts via DCs

Answer 302

Bispecific T cell engagers Made of aglycosylated anti-TAA + anti-CD3 2/ engineered disulphide bridge (stability) Allow simultaneous engagement of: - tumour associated antigens (TAAs) on cancer cells - CD3 on T cells -> activation ## Footnote Could be inactive + actvated in circulation -> slow Ab clearance enhancing clinical benefits