Week 2

Question 1

Innate immunity (details now)

Answer 1

tissue and physical elements
Cellular elements
Molecule

Question 1

Anatomical barriers to infection

Answer 1

Pathogens enter thru mucosal and epithelial surfaces to cause infections… there are different routes (air, food…)

Question 2

Tissue and physical elements

Answer 2

Epuithelial surfaces=first barrier against inf by acidic pH and antimicrobial pepride (ex: Defensins)

Skin, gut epithelium, resp epithelium, mucosal memb, saliva, hair, mucus, tears

Question 3

Cellular elements

Answer 3

Granulocyte(neutrophils)

Monocyte & Macrophages (tissue resident)

Dendritic ¢ (Immature vs MAture (concentional and plasmacytoid))

nAtural killer 4+Other lymphoid ¢

Question 4

Molecule

Answer 4

Antimicrobial enzyme: Catalytic P (digest peptidoglycan)

Antimicrobial peptide: Short aa (disrupts cell memb)

Complements

Question 5

phagocytosis

Answer 5

Engulfment and internalization of pathogens/their components upon their binding to receptors on 4 surface of phacocyte

Can lead to:
Removal and killin of pathogens

Clearing debris (when cell die (apopotosis)= release “damage associated moleclar patterns”(DAMPs) that bind to PRR

generation of peptide for presentation of T ¢ (ex: MHC)

Phagocyte:
MAcrophages (lysosome), Neutrophile (type of granylocyte) (have a granule), dendritic ¢

Question 6

Receptors involved in Phagocytosis

Answer 6

Many are PRR

Phagocytosis can occur indirectly:
Enhancement=opsonization:
Recognize soluble P bound to microbial surfaces (opsonins=soluble pattern-recognition P) that enhance phagocoytosis)… ex: antibodies, complemetn P

Question 7

Phagocytosis steps

Answer 7

1- PRR binding to PAMPS=intra¢ular signaling leading to an extension=pseudopodia

2-Enguldment of pathogens that is internalized in a membrane-enclosed endocytic vesicle=phagosome

3-Physosome+lysosome fusion=phagolysosome that acidifies and acquire antimicrobial peptide and enz to kill pathogens

**for neutrophile their “lysosome” are primary/secondary granules that fuse with phagosome

Question 8

Process that kilsl phagocytosed in phagolysosomes

Answer 8

Low pH/acidification

Hydrolytic enz (lysozomes and protease)

Oxidative attack: employs reactive oxygen species (ROS) and reactive nitrogen speacies (RNS)

Antimicrobial peptide

Question 9

Oxidative attack on phagocytosed pathogen

Answer 9

Use ROS:
damage microbial memb and intra¢ular components

Generated by phagocyte NADPH oxidase enzyme complex (of phagosome NADPH oxidase), it increase oxygen consumption (respiratory burst)

Question 10

Phagolysosome organelle impo in innate/adaptive

Answer 10

Innate: Pathogen killin, pathogen processing, pathogen presentation to sensory cytosolic PRR (TLS and NODs)

Adaptive: ANtigen degradation, antigen pricessing and antigen presentation onto MHc mol

Question 11

Neutrophils

Answer 11

Capable of phagocytosis

Not-tissue resident (recruited to site of inf (constantly in circulation0

Pus=reasut of dead and dying neutrophils

20-60% can make extra¢lar matrix NETs (neutrophil extracellular traps)=traps m/o and prevent spread
Check pic

Question 12

Ex: Neurological homeostasis

Answer 12

CNS-resident microglia (macrophage of brain)=respo for debris clean-up, brain dev, memory, learning

If sclerosis=inflammatory disease=myelin breakdown=lot of toxic debris in brain lesion microenv

Microglia and peripheral inflitrate of macrophages clean up debris to allow Homeostasis

If receptor KO of microglia doesnt have receptor… pseudopia cant be done… nor recognition

Question 13

Complement system

Answer 13

GRoup of soluble Protein that cooperate with innate and adaptive immune system to eliminate pathogen, dying ¢ and immune complexes from the body

Mostly proteases in blood
Protease: enzyme that do proteolysis (break down Protein)… name usually start with C (eg: C3a) or factor… (eg: Factor B)

Complements Protein mostly made in liver and set off chain of Rx to help clear pathogen

Key mechanisms: Increasing vascular permeability and chemotaxis (inflammation)/DEstroyinf pathogen ¢memb/ Increasing recognition of pathogens and facilitating phagocytosis (opsonization)

Question 14

Opsonization vs Phagoctosis

Answer 14

O: “coating” of surface of a pathogen by antibody/complement to make it more easily ingested by phagocyte

P: “Internalization”by a process of engulfment… memb surround material and then form intra¢re (phagosome) containg the material

Question 15

ACtivation of complement

Answer 15

Initially=inactive pro-proteases

3 ways to actiate: Classical;Alternativel;Lectin pathways

They act as a cascade: proteolytic cleavage=2 fragment

Small: “a” after name … has a specific fuction (eg C5a)
Large: “b” after name… with proteolytic act on new substrate (eg C5b)

C3 convertase:
C4b bind to C2a=C4b2a
C3b bind to factor B (Bb)=C3bBb

Converts C3 inactive to C3a and C3b (active form)

Question 16

Functional categories of coplement Protein activation

Answer 16

CAscade:

1- Initiators (C1q, MBL, ficolins)=initiate respective ocmplement Rx

2-Convertase activator and enz mediators (C3 &C5 convertase): Cleave and activate the next memb of a complement Rx sequence

3-Main outcome: Opsoninc (C3b=phagocytosis;
Anaphylatoxins(C5a)=inflammation;
Membrane attack complex)

Complement receptors=CR1 &CR3….
REgulation always happening(Inhibiting formation of MaC on host ¢

Question 17

C3 convertase: LEctin pathway

Answer 17

TRiggered by soluble Protein : Lectins (PRR but not membrane-bound) bind to pathogens surface

2Types of lectins: Mannose-binding lectin (MBL); Ficolins

Expression increase during infection
Trigger signaling cascade on pathogen surface
C3 convertase generated (C4b2a) makes C3a and C3b

Question 18

C3 convertase: Classical pathway

Answer 18

C1q bind to pathogen surface directly or to the antibodies bound to the pathogen

Can connect adaptive to innate

Once bound, trigger signaling cascade on pathogen surface and C3 generate C3a and C3b with C4b2a

C1rs cleaving protein and activate C3 too

Question 19

Convergence on C3

Answer 19

C3a: Involved in enhancing inflamamtion
C3b: Involved in Opsonization, and is a C5 convertase (make C5a and C5b)

Question 20

C3 convertase: Alternative pathway

Answer 20

picture for visuals

1 way:
HAppens after C3b has been produced by lectin or classical pathway activation

There’S an amplification loop for C3b formation (depositing more C3b mol on pathogen)

Requires FActor B and protease FActor D

C3bBb convert C2 into C3a and C3b

2nd way: VEry high [C3] (from liver), C3 undergo spontaneous hydrolysis (include factor B and D)

Overall: C3 converase (C3bBb)=unstable on pathogen surface… stabilized by factor called properdin (FActor P) secreted by neutrophils by binding to some microbial surfaces

Question 21

Downstream effect : Inflammation

Answer 21

Inflamation: REspo in cleavage of other complement molecule… C3a and C5a recruit phagocytes and promoste inflammation

If present in large amount (C3a and C5a)=anaphylactic shock

Complement receptors connect complement-tagged pathogens to effector ¢:

C3aR/C3aR on granulocyte that stimulate release of proinflammatory cytokines and granule component from basophils, eosinophils ,neutrophils, mast ¢

Question 22

Downstramed effect: Incrcease phagocytosis

Answer 22

Phagocytosis have receptor for C3b
Opsonization: more readily taken up by phagocytosis (occur via compelemtn deposition and/or ab and/or any intitors)

Question 23

Downstream effect: pathogen lysis

Answer 23

Additional complement factor create MAC, membrane-attack complex (C3-make a and b- and C5-one of componenet making MAC- involved)=Cell lysis

cascade leading to the formation of MAce: a pore in the surface of pathogen that lyses pathogen

Question 24

Negative rgulation of C activation

Answer 24

Complement-regulatory P in plasma or ¢ surface prevent complement activation from proceeding under normal/basal condition: Prevent appearance of C3 convertase Promote disappearance of C3 convertase Each pathway/process in imune sytem has a regulatory component

Question 25

Cells with PRR

Answer 25

All type of myeloid white blood ¢ Subset of the lymphoid cells: T ¢, B ¢, NK ¢ Also in other ¢: commonly exposed to infectious agents (Ex: epithelial ¢ and endothelial (blood vessels)) Cytosolic sensors of viral nucleic acids are expressed by most if not all ¢ in the body

Question 26

PRR locations and group

Answer 26

Locations: Celle surface, intracellular, secreted Groups (6): Tool-like receptors (TLRs) NOD-like receptors (NLRs) RIG-I-like-receptors (RLRs) C-type lectin receptor (CLRs) Ficolins, MBL, C1q Other Once they are bound, singlaing pathways are activated, contributing to innate/inflammatory response

Question 27

TLRs (Toll-like receptors)

Answer 27

Check pic fro visuals Intra¢re VS extra¢re receptors: logic behind corresponding PAMPs (location helps deermine what each binds) Binding of Pamps activate signaling pathways (diff TLR recruit diff adaptor protein and link protein-brinding parners tgtr and facilitate large signaling complexes)

Question 28

Different adaptor P

Answer 28

Lead to diff event-transcription factors-: NF-kB: transcitption factor activation Interferon regulating factor (IRF) pathways MAP kinase pathway downstream transcription factors (AP-1) Signaling leads to activation of transc factor-->transcription of innate immune/pro-infammatory gene... once expressed=specific impact

Question 29

Signaling and gene expression

Answer 29

Signaling cascade triggered Involved many P Phosphorylation=addition of P group to a mol: leads to activation of transcription factors which translocate into nucleus to activate gene exp Key mol: Adaptor P and transc factors

Question 30

Signaling basics

Answer 30

Ligand-Induced REceptor Dimerization (binding to PRR) REcruitement/ACtivation of kinase and Adaptors SEcond MEssenger Activation/Nuclear translocation of transc exp Changes in Gene exp Post transciptional or post translational mod Fctnal response

Question 31

CLR (C-type REceptors)

Answer 31

Memb receptor (only)-on cell surface- Bind carbohydrate on pathogen and some allergens ACtivated tyrosine kinase trigger signaling cascade: CaRD adaptor P IRF5 activation MAPK pathways activation resulting in activation of AP-1 and NF-kB Induce the exp of inflammatory cytokine

Question 32

RLR (RIG-I-like receptors)

Answer 32

Cytosolic PRR REcognize VIRAL dsRNA and certain ssRNA Mitochondrial antiviral signaling protein (MAVS) Trigger signaling pathways that activate: IRFs (transc factor) NF-kB

Question 33

NLR (NOD-like Receptors)

Answer 33

Nucleotide oligomerization domain (NOD) Cytosolic PRR Recognize peptidoglycan from bac cellwall (must enter the cytosol in the phagosome) CAn trigger NF-kB, AP-1 &IRF signaling Activate caspase-1 protease (cleaves P): Caspase-1 cleaves IL-1B/IL-18 into active forms for release (pro-inflammatory cytokine) POST TRANSLATION MOD PIC!!!

Question 34

PRR signaling pathways (end of week 2)

Answer 34

PRR recognize PAMPS: Consider type of pathogen and its location Signaling cascade-->series of P Mod such as phosphorylation & ubiquitunation(process of attachment of one or many subunit to a target P, which can mediate their formation for further signalling) ACtivation of trasc factor (gene exp dna to mrna to P)...can result to post-trans and port traslational mod... carry out a fct