Apararea antivirala

Celulele NK

RIC

Apararea antiinfectioasa Organism Reprez Fag

(II) CK (II)

NK (II)

Complement Ac neutral

CTL

VIRUSURI

•Gripă •Oreion •Pojar •Rinovirus

+++ +++ +++ +++

IFN

+++ +++ +++ +++

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+++ +++ +++ +++

+++ +++ +++ +++

BACT INTRA CELULARE

•Listeria m •Legionella •Mycobact •Ricketsia

--- --- --- ---

+++ +++ +++ +++

--- --- --- ---

+++ +++ +++ +++

+++ +++ +++ +++

BACT EXTRA CELULARE

•Staph spp •Strep spp •Neisseria •Salmonella

+++ + +

+++

--- --- --- ---

+++ + +

+++

+++ +++ +++ +++

--- --- --- ---

Apararea anti-virala

Raspunsul Imun mediat Celular Scop: 1. Apararea impotriva microbilor cu habitat

intracelular: – Celule fagocitare

– Celule non-fagocitare =>

• Recunoasterea & distrugerea celulor expun : – AgEndogene+MHC I (infectie/ tumorale): cel singenice

(proprii/self)

– Ag + MHCI ≠ : Cel allogenice (non-self) (grefe tisulare /organ)

Mecanismul de distrugere:→ Citotoxicitate

RIC: celule

I. Celule efectoare 1. specifice:T CD8+ (citotoxice, LTC)

2. ne-specifice: Natural killer (NK)

Roluri: • Recunoasterea celulelor-tinta

(mecanisme diferite)

• Distrugerea celulelor-tinta

(mecanisme similare)

II. Celule Auxiliare:

1. APC (→ TCD4⁺)

2. T CD4⁺ (TH) → TCD8⁺ (Mφ)

Rol: activarea completa a LT CD8⁺

APC

1

2

Apararea antivirala innascuta si adaptata

RI antiviral: Innascut si Adaptat

Interferoni • Structura Prot & Gp → familii:

– Tip I (α, β, ω,ξ,κ) -secretati de • celulele infectate viral • CD, • Leucocite (α) • Fibroblaste (β)

– Tip II ( γ) – secretati de

• celulele imune efectoare RIC: TH1, LTC, NK • APC: profesionale

• Stimuli: – Infectia virala (α β, γ) – Status inflamator (γ)

• Receptori: – RTip I (com) → IFN-αR1 & R2 – R Tip II (γ) →IFN-γR1 & R2

• Efecte: Similare • + transcriptiei gene ~IFN • +genei ds-RNA PKR (enzima) => blocarea sintezei proteinelor virale

IFN-regulatory factor 9=

ISRE-IFN-stimulated response elements

STAT,signal transducer & activator of transcription

Principalele functii ale familiei

IFN

1. + celulele sanatoase ― + genele → secretie PKR→ ―blocarea replicarii virale in celulele sanatoase

2. activeaza MФ 3. mobilizeaza NKs

Efectele anti-virale ale IFN α/β

1.fosforilare

2. Auto- Fosforilare

PKR PKR

eIF2α= α subunit of eukaryotic initiation factor 2

PKR=protein kinase (dsRNA-dependent)

Apararea antivirala innascuta si adaptata

RIC: celule I. Celule efectoare 1. specifice:T CD8+ (LTC)

2. ne-specifice: Natural killer (NK)

Roluri: • Recunoasterea celulelor-tinta

(mecanisme diferite)

• Distrugerea celulelor-tinta

(mecanisme similare)

II. Celule Auxiliare:

procesare Ag →MHC I, II

1. APC (→ TCD4⁺) 2. TCD4⁺ (TH) → TCD8⁺

Rol: activarea completa a LT CD8⁺

APC

1

2

remember:

Hematopoiesis

I. Celulele imunitatii innascute remember:

Celule NK

• I linie de aparare impotriva:

1. Celulelor infectate viral

2. Celulelor tumorale

3. Altor patogeni intracelulari

• Implicate in: 4. Respingerea grefei

5. Autoimunitate

6. Avortul Spontan

NK Cell

Tumor Cell

remember:

Celule NK: caracteristici (I)

Denumirea: semnalizeaza functia citotoxica

Localizari: circulante: 5-15% populatia Lf organe: splina, ficat, uter

Identificare: CD3⁻ CD56⁺ CD16⁺

CD3 ⁻ → implicat in transducerea semnalului prin TCR CD56 ⁺ → ? CAM CD16 ⁺ → receptor tip Ig FcγRIIIA (recunoaste Fc IgG→ fctie efectoarea NK (ADCC)

• 3 Subseturi – Majoritatea: CD3- CD56dimCD16+

• Contin perforine si granzyme→ citolitica • Moduleaza secretia CK

– Minoritate: CD3_CD56brightCD16- • Secreta cant ↑CK (IFNγ,TNFα, IL-10) • Activitate citolitica redusa

– Rare: CD3-CD56-CD16+

• Activitate citolitica foarte redusa • Secreta numai cant scazute de CK • ? Precursori CD3- CD56dimCD16+

Celule NK: caracteristici (II)

Receptori* Kill Activator Receptors (KAR) caracteristici Kill Inhibitor Receptors (KIR) Recunosc: celulele proprii infectate celulele proprii modificate Recunoastere: Lig (P/DAMP) → cel proprii modificate (KAR) (Nespecifica) Lig (MHC I) → cel proprii nucleate N (KIR) Activare: echilibru semnalele activatoare ~ inhibitoare Actiuni: liza celulelor-tinta secreta CK implicate in apararea antivirala

Celule NK: caracteristici (III)

Celule NK: importanta

• RIC mediat NK în infecțiile cu: 1. Arenavirus (vs coriomeningitei limfocitare)

2. Virusul herpetic (vs Herpes simplex)

3. Ortomixovirusuri (vs gripal)

4. Picornavirus (vs Coxsackie)

• Timpul de raspuns: – Răspunsurile maxime celule NK: ore / zile

– Răspunsurile maxime celule T & B: > 7zile

Vivier, E. et al. Innate or adaptive immunity? The example of natural killer cells. Science. 331, 44-49 (2011).

Receptori NK

Ce recunosc NK? • Prezenta & absenta Selfului : MHC I: HLA-A, -Bw, -Cw, -G

• Self-ul indus/ modificat: proteine care semnalizeaza stresul celular:

– HSP, – MIC-A, MIC-B, (MHC I chain-related proteins type A, B)

Fam Receptori NK

Natura

Moleculara Liganzi

Coresp.

soarece

KIR (killer Ig-like R) Superfamilia Ig HLA-A, -Bw, -Cw, -G gp49

ILT/LIR Superfamilia Ig HLA Cls Ia (-G) LRC

CD94/NKG2 (KLR) C-type lectin-like HLA Cls Ib (-E) NKC / Ly49

KAR (NKG2D, KLRK1) C-type lectin-like MIC A,B & MHC I-like NKG2D

NCR Superfamilia Ig Hemaglutinine Virale, NCR

I. C-type lectin:

CD94 (→ NKG2A) – Ligand: MHC I

– Semnal → ITIM

II. Ig-like family:

KillerIg-like R*: – Ligand: MHC I I

– Semnal→ITIM

Receptorii Inhibitori ai NK (KIR*)

Caracteristic: ITIM =Immunoreceptor Tyrosine based Inhibitor motif

Dupa Abas at al. 2012 Elsevier/Saunders

Mecanisme de Activare ai KIR

• Celulele nucleate self N (sanatoase) – Legarea ligandului (MHC I) la receptorul

NK → Da semnal inhibitor – NK „recunoaste‟ tinta drept celula self+

sanatoasa→ – NK se detaseaza fara sa lizeze celula

• Celule infectate/transformate malign – Pierderea ligandului inhibitor (MHC I)→ Nu

semnal inhibitor – NK „recunoaste‟ tinta drept celula “self

absent”/„missing self‟ – DA liza celulara: degranulare → – perforinei & granzimelor

Receptorii Activatori ai NK (KAR)

I. C-type lectin:

NKG2D: – Leaga MIC-A,B

– Semnal ≠ITAM

Caracteristic: ITAM

II. Ig-like family: CD16 (Fc γ RIIIa)

Leaga IgG Semnal→ITAM*

Dupa Abas at al. 2012 Elsevier/Saunders

Mecanisme de Activare ai KAR

• Celulele nucleate self N (sanatoase) – LIGAND: molecule stres => – Fara ligand recunoscut de KAR → Fara

semnal activator – NK “recunoaste” tinta ca fiind N,

sanatoasa → – NK se detaseaza fara sa lizeze celula-

tinta

• Celule infectate/transformate malign – Recunoasterea ligandului stres→ Da

semnal activator – NK “recunoaste” tinta ca fiind

• “self indus”: ( MIC-A, B, HSP) • “non-self” (proteine virale + molecule MHC-

like) – DA liza celulara: degranulare→ perforina &

granzime

Recunoasterecelule

infectate (maligne)

1 2

Asocierile cu Boala ale Combinatiilor Alelice KIR & HLA

Disease KIR HLA Disease progression Proposed contribution by KIRs AIDS 3DS1

3DS1 homozygous HLA-Bw4Ile80

No HLA-Bw4Ile80 Decreased Increased

Less inhibition More inhibition

HCV infection

2DL3 homozygous

HLA-C1 homozygous

Decreased

Less inhibition

Cervical neoplasia (HPV-induced)

3DS1

No 3DS1

HLA-C1 homozygous

and no HLA-Bw4 HLA-C2 and/or HLA-Bw4

Increased

Decreased

Less inhibition

More inhibition

Malignant melanoma

2DL2 and/or 2DL3

HLA-C1

Increased

More inhibition

Psoriatic arthritis

2DS1 and/or 2DS2

HLA-C1 homozygous or

HLA-C2 homozygous

Increased

Less inhibition

Type I diabetes

2DS2

HLA-C1 and no HLA-C2,

no HLA-Bw4

Increased

Less inhibition

Preeclampsia

2DL1 with fewer

2DS (mother)

HLA-C2 (fetus)

Increased

More inhibition

Rajagopalan, S., Long, E. Understanding how combinations of HLA and KIR genes influence disease. J. Exp. Med. 201, 1025-1029 (2005).

Mecanismele efectoare ale NK

I. Citotoxicitate A. Directa:

― Liza osmotica a celulei tinta (perforine) ― Apotoza celulei-tinta (granzime B)

B. Indirecta: • Apotoza celulei-tinta (IFN →+FasL; TRAIL=> +

caspaze) C. *Mecanism mediat de Ac (ADCC: Ab dependent cellular

cytotoxicity)*

Stimulata de CK II: ―IL-12 (GF) ―IL-15 (GF) ―IL-18 ―IFN α/β

Mecanismele citotoxice ale NK Citotoxicitate directa:

-Degranularea

1. Adeziunea inter-celulara, 2. polarizarea citoscheletului

1.Adeziunea , 2.Polarizarea

citoschelet 3. Liza eficienta a

celulei-tinta

Etape: 1. Adeziunea intercelulara 2. Polarizarea citoscheletului 3. Degranularea veziculelor litice 4. Liza celulei -tinta

Mecanismele citotoxice ale NK

Smyth, M. J. et al. Activation of NK cell cytotoxicity. Mol. Immunol. 42, 501–510 (2005).

Mecanismele Efectoare ale NK (II)

II. Secretie de citokine: 1. +Activitate antivirala: secretia de IFNs 2. Amplifica activarea Mφ 3. + mobilizarea NK

Dupa Abas at al. 2012 Elsevier/Saunders

Mecanisme virale de “evadare”

1. Variatia antigenica: – Virusul gripal, HIV, rinovirus

2. Productia de modulatori imuni: – Receptori solubili ai CK → actioneaza ca “ momeli”

=> blocrea actiunii CK (poxvirusurile) – CK imunosupresoare (ex EBV prod IL-10)

3. Angajarea unor cai de inhibare: – LCMV (șoareci), HIV (oameni): PD-1

4. Infecția celulor sistemului imunitar – HIV

5. Inhibarea procesarii Ag pe calea MHC I – Diferite mecanisme: CMV, HSV, EBV, adenovirus

2. Inhibarea procesarii Ag pe calea MHC I