.

Outline

Introduction to autophagy

Autophagy in innate immunity

Autophagy in adaptive immunity

Conclusion

References

Autophagy

• An intracellular homeostatic mechanism

important for the degradation of waste

components from the cytoplasm in acidic

lysosomal compartments.

• Targets: Range of pathogens with particular

emphasis on intracellular bacteria.

Types of Autophagy :

ImmunologyVolume 141, Issue 1,

Autophagy pathway:

Autophagy in immune system

Autophagy is most ancient of immune

defences.

Autophagy has now evolved multifacetted

role.

Autophagy has now become a bonafide

regulator of both innate and acquired

immune system.

Autophagy in innate immunity

Autophagy and pattern recognition patterns.

Autophagy and bacteria handling.

Autophagy and cytokines.

TLR4 is able to induce autophagy in murine macrophages following stimulation with lipopolysaccharide (LPS). ( Shi CS, Kehrl JH.)

• LPS stimulation of TLR4 was shown to increase the clearance of Mycobacterium tuberculosis by autophagy. (xu Y, Jagannath C,

Liu XD)

• TLR9 Front. Immunol., 25 June 2014

Autophagy and PRRs

Autophagy can also play a role in facilitating

recognition of PAMPS by TLRs

Autophagy was able to

deliver viral ligands to

TLR7 in plasmacytoid

dendritic cells (pDCs)

following vesicular

stomatitis virus and

Sendai virus infection

resulting in type I

interferon production (lee et

al)

Front. Immunol., 25 June 2014

Autophagy and NLRs

• Activation of the NLRs in mice

leads to recruitment of

Atg16L1 at the plasma

membrane to the site entry of

invading Shigella flexneri and

Listeria monocytogenes,

resulting in their sequestration

in autophagosomes and

subsequent destruction. Travassos

LH, Carneiro LA, Ramjeet M et al.)

Annual Reviews

Annual Reviews

In humans, the treatment of

DCs with the NOD2 ligand

muramyldipeptide (MDP) has

been shown to induce autophagy (Cooney R, Baker J, Brain O et al.)

Autophagy and NLRS

• NLRs induce autophagy

• Absence of NOD2 signalling resulted in increased

bacterial burden, attributed to poor autophagy

induction. (Lapaquette P, Bringer M, Darfeuille-Michaud A.)

NLRs can also inhibit autophagy

• NLRP4 can inhibit

autophagy through its

ability to bind and inhibit

the action of Beclin 1.

Front. Immunol., 21 November 2013

Autophagy and RLRs

• Acts downstream of virus-sensing pathways

mediated by RLRs.

• Treatment with the polyinosine-polycytidylic acid,

acting through the RLR is able to induce autophagy

in melanoma cells resulting in autophagy-dependent

cell death.(Tormo D, Checinska A, Alonso-Curbela D et al)

Negative regulation of RLRs by autophagy

• Atg5-deficient murine macrophages have increased

RLR signalling mediated by enhanced reactive

oxygen species production owing to an increase in

mitochondrial volume.(Tal MC, Sasai M, Lee HK, Yordy B, Shadel GS,

Iwasaki A)

Autophagy and bacteria handling

1. Uptake of cytosolic bacteria:

• Autophagy leads to uptake of cytosolic bacteria

mediated by a central adaptor protein called p62

• Listeria monocytogenes persists in cell due to

inhibition of autophagy by Listeriolysin,

Phospolipase C and actin polymerization protein A (Yoshikawa Y, Ogawa M, Hain T et al)

2. Removal of vacuolar bacteria

Autophagy facilitates the fusion of BCG-

containing vacuoles with lysosomes to facilitate

mycobacterial killing (Birmingham L, Canadien V et al)

When infected with M. tuberculosis, mice with a

myeloid lineage-specific deletion of Atg5

exhibited enhanced mycobacterial burden

compared with wild-type controls, alongside

increased tissue necrosis and lung pathology. (Castillo

EF, Dekonenko A, Arko-Mensah J et al.)

3.Bacteria induce autophagy

• Pseudomanas aeruginosa is able to induce

autophagy in the alveolar macrophages cell line

MH-S.(Yuan et al)

• Knockdown of beclin 1 with small interfering RNA

or treatment with the autophagy inhibitor 3-MA

resulted in a marked increase in bacterial load

whereas treatment with the autophagy inducer

Rapamycin improved bacterial clearance. (Watson RO,

Manzanillo PS, Cox JS)

NETs

• PMA-induced NETosis was found to be dependent

on autophagy and treatment of neutrophils with the

autophagy inhibitor wortmannin was able to exert

an inhibitory effect on NET formation.

• Pharmacological manipulation of autophagy could

induce or inhibit NET formation and mediate the

delivery of factors important for NET function (Itakura

A, McCarty OJT)

Autophagy and cytokines

• Interferon- γ ((Th1) cytokine ) is a potent

inducer of autophagy while the IL-4 and IL-

13(Th2 cytokines ) have been shown to have

inhibitory effect

Autyophagy and cytokines

• Role in the biogenesis and secretion of various

proinflammatory cytokines.

• Atg16L1-deficient macrophages exhibit

enhanced IL-1 β and IL-18 secretion following

stimulation with LPS.

Autophagy and cytokines

Production of multiple other cytokines is

enhanced in the absence of autophagy

Increases in IL-1α, IL-12, IL-17 and CXCL1

were all observed in Atg5 fl/fl LysM-Cre+ mice

compared with wild-type controls in response

to M. tuberculosis infection.

• TNF-α and IL-6 secretion are also regulated by

autophagy;

• Inhibition of autophagy with 3-MA or knockdown of

beclin 1 and Atg7 promotes IL-1α, IL-1β and IL-23

secretion by macrophages and DCs and this in turn

augments innate secretion of IL-17, IFN-γ and IL-

22 by γδ T cells.(Peral de Castro C, Jones SA, Cheallaigh CN et al.)

Autophagy and cytokines

Autophagy and adaptive immunity

Autophagy and antigen presentation• MHC Class I presentation

• MHC Class II presentatioin

Autophagy in T cells

Autophagy in B cells

Autophagy and antigen presentationMHC Class I presentation

• Limited evidence exists that autophagy plays a role in the conventional MHC class I pathway.

• No improvement in MHC class I presentation of a viral epitope when it was conjugated to LC3, a mechanism that was able to enhance the presentation of MHC class II antigens.(Schmid D, Pypaert

M, Munz C)

• Multiple other studies have also failed to report a requirement for autophagy in MHC class I presentation.(Lee HK, Mattei LM, Steinberg BE et al.)

Autophagy and MHC Class I….

Inhibition of autophagy was found to decrease

MHC class I surface expression in B16 murine

melanoma cells and subsequent tumour cell

cytolysis by CD8+ T cells.(Li B, Lei Z, Lichty BD, et al)

Autophagy has been implicated in an alternative

pathway of MHC class I presentation that exists in

DCs and macrophages, termed cross-presentation.

Autophagy and MHC class I Ag presentation

.

Autophagy and antigen presentationMHC Class II presentatioin

Prominent role of the lysosomal system in MHC

class II presentation have linked autophagy to this

form of antigen presentation.

Traditionally, MHC class II antigens were believed

to be sourced from the extracellular space following

phagocytosis by antigen-presenting cells.

MHC Class II …

• More than 50% of MIICs were observed to receive

input from autophagosomes.(Schmid D, Pypaert M, Munz C)

• Analysis of the human B lymphoblastoid cell line

showed that some MHC class II epitopes were

derived from intracellular sources and starvation-

induced autophagy could enhance the presentation

of intracellular antigens on MHC class II

molecules.(Dengjel J, Schoor O, Fischer R et al.)

MHC Class II…

Use of starvation and Rapamycin in macrophages

and DCs can also increase MHC class II

expression of a mycobacterial antigen following

phagocytosis of BCG (Gerland LM)

The secreted antigen, Ag85B, was found colocalized

with LC3+ autophagosomes suggesting that

autophagy may capture antigens following their

escape from the phagosome and deliver them to the

lysosome to prime CD4+ T cells.

MHC Class II…

• Conjugation of the influenza matrix protein 1 to

LC3 could also enhance the priming of antigen-

specific CD4+ T cells.

• Mice with a DC-specific deletion of Atg5 have

impaired CD4+ T-cell priming in response to

herpes simplex virus infection (Lee HK, Mattei LM, Steinberg

BE et al)

Autophagy in the immune system

ImmunologyVolume 141, Issue 1

Autophagy and T cells

Autophagy is constitutively present in T cells (Gerland

LM et al)

T cell development and selection (Nedjic J, Aichinger M,

Emmerich)

T cell deletion in Atg5-/- leads to increased apoptosis due to loss of organelle quality.(Parekh VV, Wu L, Boyd KL et al.)

Proliferation following activation by Ag (Wang X, Gao Y,

Tan J et al.)

Loss of ER homeostasis (Jia W, He Y)

Regulation of energy metabolism (Hubbard VM, Valdor R,

Patel B)

iNKT cell development (Parekh VV, Wu L, Boyd KL et al.)

Autophagy and B cells

B cell development (Miller BC, Zhao Z, Stephenson LM et al.)

B cell homeostasis (Mortensen M, Ferguson DJ, Edelmann M, Kessler B,

Morten KJ, Komatsu, Simon AK. et al)

Differentiation of B cells into Plasma cells (Pengo N,

Scolari M, Oliva L et al.)

Regulated Ig secretion

Conclusion

Autophagy is implicated in pathogen sensing, phagocytosis, the removal of intracellular pathogens, and cytokine production.

Role of autophagy in MHC Class II well known but in Class I not understood

Autophagy is essential for the homeostasis of lymphocytes

Role of autophagy in certain functions of immune system is unclear and needs further work

References

• Autophagy in the immune system :Daniel J. Puleston1 and Anna Katharina Simon

• journal of immunology published by John Wiley & Sons Ltd, Immunology, 141, 1–8 :2013

• Autophagy and cytokines :James Harris Immunology Research Centre, School of

Biochemistry & Immunology, Trinity College Dublin, College Green, Dublin 2, Ireland

• Autophagy and Its Role in MHC-Mediated Antigen Presentation :Victoria L. Crotzer and

Janice S. Blum J Immunol 2009;

• Autophagy and pattern recognition receptors in innate immunity; Monica

Delgado,Sudha Singh,Sergio De Haro ,Sharon Master etal Immunological Reviews 2009 Vol.

227: 189–202

• TLRs, NLRs and RLRs: a trinity of pathogen sensors that co-operate in innate

immunity :Emma M. Creagh and Luke A.J. O’Neil TRENDS in Immunology Vol.27 No.8

• Autophagy and the Immune System: Petric Kuballa, Whitney M. Nolte, Adam B.

Castoreno, and Ramnik J. Xavier Annu. Rev. Immunol. 2012. 30:611–46

• Pattern recognition receptors and autophagy Ji Eun Oh and Heung Kyu Lee Front. Immunol., 25 June 2014 | doi: 10.3389/fimmu.2014.00300