phagocytosis and antigen presentation

doi:10.1006/smim.2001.0334, available online at http://www.idealibrary.com onseminars in IMMUNOLOGY, Vol. 13, 2001: pp. 373–379

Phagocytosis and antigen presentation

Colin Watts a and Sebastian Amigorena b

Foreign antigens come in many different shapesand sizes and to induce a response requires thatthey be converted to some common ‘currency’ thatthe T lymphocyte system can deal with. This is thenow familiar peptide/MHC complex. Our detailedknowledge of how these complexes are assembledin cells has come from analysis of the biosynthesisof MHC molecules and the fate of endogenous orexogenous antigens. The processing of exogenousantigens follows their uptake into professionalantigen presenting cells by some type of endocyticevent.1 This can involve receptor-mediated uptakethrough the clathrin coated pit system, pinocytosis,particularly macropinocytosis as a consequence ofmembrane ruffling and phagocytosis. Although itmight be argued that more effort has been expendedanalysing the first two modes of antigen uptake, pro-cessing of phagocytosed antigens in different forms isincreasingly recognised as central to the induction ofimmune responses. Indeed, a landmark experimentin this field, demonstrated the requirement formetabolism of a phagocytosed bacterial pathogenbefore a T cell response could be induced.2

In this short review, we discuss progress that hasbeen made in understanding the processing andpresentation to T cells of phagocytosed antigensubstrates.

Antigen presentation overview

Generally class I and class II MHC moleculescapture peptides in the endoplasmic reticulum andendosome/lysosome system, respectively. In the caseof class I MHC molecules, peptides, derived mostlyfrom newly synthesized proteins,3,4 are generatedby the multicatalytic proteasome, transported

From the aDepartment of Biochemistry, University of Dundee, Dundee,DD1 5EH, UK and bINSERM U520, Institut Curie, 75005 Paris,France.

c©2000 Academic Press1044–5323/01/060373+ 07/$35.00/0

through the TAP complex and can be subjected tofurther N-terminal trimming by as yet unidentifiedpeptidases resident in the E.R. to generate the 8and 9 residue peptides required by class I MHCmolecules reviewed in References 5,6. Recent studiesby Shastri and colleagues have revealed cytosolicand E.R. located processing intermediates as well asevidence that trimming occurs following binding toclass I MHC molecules.7,8 The assembly of peptideswith class I MHC is chaperoned by a number ofmembrane bound (calnexin, tapasin) and soluble(calreticulin, Erp57) E.R. proteins.9 The peptideligands for class II MHC molecules are generatedby lysosomal and endosomal proteases. Unlikeclass I MHC, peptide generation and capture byclass II MHC molecules takes place in the samecompartmental system. Class II MHC moleculesdisplay peptides of heterogenous length generatedfrom endocytosed protein substrates subjected todigestion by lysosomal cysteine and aspartic proteasesreviewed in Reference 10. Most likely, initial captureis followed by trimming, as for class I MHC, but thisis not yet clearly documented. As for class I MHC,the overall production of assembled class II MHCmolecules is a chaperoned event. The invariantchain engages the newly synthesized class II αβ

dimer soon after synthesis, boosts its export from theE.R. and targets a nine chain complex (3 × Iiαβ)to the early endosome system.11 In addition Ii actsas a surrogate peptide stabilizing the αβ dimer. Itsremoval, essential for antigen presentation, is alsoinitiated by endosomal/lysosomal proteases andcompleted by the HLA-DM protein, which appears tofacilitate peptide exchange until a suitable (i.e. tightbinding) ligand has been captured.12,13

Class II MHC-restricted antigen processing hasbeen extensively analysed in B lymphocyte lines andmore recently in dendritic cells (DC) following therealisation that these cells possess several attributesthat make them uniquely poised to initiate immuneresponses.14 One key attribute discussed belowis the ability to present exogenous antigens notonly on class II MHC molecules, but also on class

373

C. Watts and S. Amigorena

I MHC molecules. Although there are reportsof presentation of phagocytosed antigens by Bcells, we limit our discussion to the phagocytosisand presentation of antigens by macrophages anddendritic cells. Due to space constraints, we donot cover some important areas, for example, theability of some phagocytosed microorganisms such asMycobacterial species to interfere with the machineryof antigen processing.

Presentation of phagocytosed antigens on classII MHC molecules

A diverse array of phagocytic substrates have beenstudied in the context of presentation on class IIMHC molecules. These include red blood cells,antigen coated latex (or other synthetic) beads andliposomes. Among the more physiological substratesexplored, are whole bacteria and yeast, necroticand apoptotic cells (specially those infected withviruses or microbes), immune complexes and othermacromolecular assemblies. Both macrophages anddendritic cells have been used to study antigenpresentation following phagocytosis.

Macrophages

For antigens taken up via clathrin coated pitsand macropinocytosis, processing and loadingonto class II MHC molecules is believed to takeplace within the multivesicular and multilamellarcompartments that make up the endosome/lysosomesystem of professional APC. Where class IIMHC molecules capture peptides derived fromphagocytosed substrates is less obvious. Hardingand colleagues have performed a series of studiesusing peritoneal macrophages to address whetherphagosomes containing latex bead associatedantigen are fully competent as antigen processingand class II MHC loading organelles.15 Phagosomeanalysis by flow organellometry and isolation onsucrose gradients, demonstrated that phagosomesprogressively acquired class II MHC molecules,invariant chain and H2-DM. Importantly, specificovalbumin 323–339/I-Ad complexes were detectedin isolated latex-ovalbumin loaded phagosomes usingT cell hybridomas. Ramachandra and colleaguesruled out the possibility that class II/peptide loadingoccurred in endosomal compartments followed bysubsequent transport to phagosomes by isolatingseparate phagosome populations from the same cells.

Only those loaded with the relevant latex-antigenbeads possessed specific peptide/MHC complexes.16

Although phagosomes contained MHC class IIderived both from the plasma membrane (recycling)and from the secretory pathway (newly synthesised)in approximately a 1 to 2 ratio, it was the latternascent population of class II MHC molecules thatparticipated in presentation of phagocytosed anti-gens.15 Taken together, these detailed studies revealmacrophage phagosomes to be fully competentand autonomous antigen processing organelles. Inanother study, distinct processing and MHC class II(newly synthesized versus recycling) requirementswere observed for two different epitopes on theM5 cell surface protein of viable Steptococcuspyogenes.17 Whether both these epitopes weregenerated in phagosomes was not investigated.

Dendritic cells

Dendritic cells (DC) were at one time believed tobe non-phagocytic. It is now clear that this is onlytrue of terminally differentiated DC and that freshlyisolated or cultured immature DC are phagocyticallyactive although macrophages may be able to handlea broader range of phagocytic substrates.18,19 A keydifference between macrophages and DC is thatphagocytosis by DC usually triggers an array of vigor-ous responses that are associated with DC maturationand antigen presentation. Phagocytosis may evenboost the differentiation of DC from precursors.In an in vitro model of transendothelial migration,monocytes were observed to differenciate into DCand this was more efficient when the monocytes hadrecieved a phagocytic stimulus.20 Other changestriggered by phagocytosis include the secretion ofboth inflammatory and immunoregulatory cytokinesand chemokines, the increased surface expression ofMHC, adhesion and co-stimulatory molecules and,significantly, the shut down of further phagocyticactivity.21 All this results in efficient antigenpresentation to CD4 T cells following phagocytosisof bacteria of which there are many reports (e.g.Reference 22). In vivo, ingestion of phagocytic mealsis accompanied by DC migration. For example,intravenous administration of particulate ‘antigens’(latex beads or carbon) resulted in phagocytosisby DC in the liver, which then migrated throughafferent lymphatic vessels and were found later in theT cell areas of draining lymph nodes and spleen.23

Although DCs can take up and present solubleproteins on class II MHC molecules, uptake by

374


phagocytosis of immune complexes, cell fragmentsand other macromolecular aggregates usually deliversmuch larger amounts of protein to the processingsystem and as a result is more efficient. Remarkably,phagocytosis of such physiological substrates byDC often results in presentation on class I MHCmolecules, a pathway not observed in other class IMHC expressing cells (except macrophages undercertain conditions). We deal with this importantphenomenon of ‘cross-presentation’ to CD8 T cellsin more detail below, but it is worth noting that‘cross-presentation’ on class II MHC molecules alsooccurs under these conditions and may lead either totolerance or activation of CD4 T cells. For example,DCs expressing I-Ab class II molecules were ableto generate a class II/peptide complex recognisedby the Y-Ae antibody following phagocytosis andprocessing of cellular fragments derived from eitherapoptotic or necrotic cells expresssing the I-Eαclass II chain (Y-Ae is specific for I-Ab plus the I-Eα56–73 peptide).24 Intracellular processing of thephagocytosed cell substrate was demonstrated byseparating phagocytic capture of cell fragments fromsubsequent epitope generation with an NH4Cl blockon processing during the capture phase followedby subsequent wash-out and generation of theY-Ae epitope. Interestingly the same complex waspresented by draining lymph node DCs in H-2b (B6)mice that had been injected with H-2d DC (or B6.I-Etransgenic DC) in the footpad.24 Inaba et al. suggestthat DC migrating from the periphery, where theyhave taken up cellular fragments from normal cellturnover, may in turn themselves die in draininglymph nodes, become phagocytosed by local DCswhich then present their processed contents toinduce T cell tolerance rather than activation.25

Under other conditions, capture of apoptotic ornecrotic cell fragments activates, rather than tolerises,both CD8 (see below) and CD4 T cells. One situationwhere uptake of apoptotic cells may be activatingrather than tolerising, is when apoptosis is inducedby foreign pathogens. For example, infection ofmacrophages by Salmonella typhimurium inducesapoptosis of the phagocytic cells.26 Ovalbuminexpressed by the bacteria was presented on bothclass II and class I MHC molecules following uptakeof apoptotic macrophages by bystander DC. Thuswhile presentation of phagocytosed apoptotic cellsmay be tolerogenic under non-infectious conditions,induction of apoptosis by bacteral or viral (see below)infection may provide the appropriate triggers forT cell activation.

The CD1 family of antigen presenting moleculesalso capture antigen in the endocytic pathwaybut present lipid rather than protein antigens, forexample from mycobacteria.27 Interestingly, differentmembers of the family seem to patrol different partsof the endosome system28 and it seems, differentphagosome populations as well. Whereas CD1b wasfound in mature phagolysosomes CD1a was foundin newly formed phagosomes analagous to earlyendosomes.29 Thus distinct bacterial lipids andglycolipids may be captured by CD1 molecules eitherin different phagosome populations, or followingtheir release and transport to conventional early andlate endosomes.

Phagocytosis and MHC class I-restricted antigenpresentation

In vivo cross priming

In 1976, Bevan showed that transplantation ofmale H-2b or H-2d cells in female H-2bxd miceprimed anti-HY CTL responses restricted by both band d MHC class I molecules30 and called this invivo phenomenon ‘cross priming’. More recently,cross priming was demonstrated in the case ofanti-tumor immune responses and of immuneresponses against certain viruses.31,32 Several recentstudies analysed cross priming of bacterial andviral antigens. Initiation of CTL responses againstL. monocytogenes epitopes, against an OVA epitopeexpressed in vaccinia virus, and against epitopes frompoliovirus, influenza (Flu) and LCMV, all requirecross priming to initiate immune responses.32–34

Cross priming was found to dependent on theexpression of TAP transporters in hematopoieticcells, in the cases of epitopes expressed by vacciniavirus, poliovirus and Flu, but not for an epitopefrom LCMV. TAP dependent cross priming, however,was more efficient than TAP-independent crosspriming for the same epitopes. Altogether, thesestudies suggest that the initiation of most anti viraland bacterial CTL responses requires phagocytosisof infected cells by APCs and cross presentationof pathogen-derived epitopes on MHC class Imolecules.

In vitro cross presentation

Thus, the cells that initiate cytotoxic immuneresponses (hematopoietic APCs), are not the ones

375


that express the antigens (allogeneic cells, viral-infected or tumor cells). Therefore, antigens needto be transferred from the cells that make them intothe APCs. After uptake by APCs, these antigens needto be presented on MHC class I molecules to specificCTL precursors. This process of antigen uptake andMHC class I-restricted presentation in vitro to CD8+T cells is referred to as ‘cross presentation’.

The mechanisms of antigen transfer and uptake forcross presentation in vitro, were extensively analysed.Interestingly, phagocytosis35,36 and macropinocyto-sis37,38 are privileged routes for antigen uptake forcross presentation in macrophages and DCs. In mostcases, however, efficient uptake for cross presentationrequires specific receptors. Potential receptors forphagocytosis in DCs and macrophages include FcRs,complement receptors and lectins (for a review, seeReferences 14,39). The most extensively analysedphagocytosis pathway in macrophages and DCs, isthat of apoptotic cells, an optimal source of bacterial,viral and tumor antigens for cross-presentation.In macrophages, apoptotic cells are engulfedthrough multiple receptors, including a receptorcomplex composed of integrins (αvβ3), CD36 anda soluble protein, thrombospondin-1 (TSP-1)40 anda phosphatidylserine receptor.41 In DCs, a similarreceptor complex for apoptotic cell phagocytosiscontains αvβ342 and/or αvβ5.43 A cytosolic complex,composed of CrkII, DOCK-180 and Rac1 is requiredfor phagocytosis through αvβ5.44

Efficient cross presentation occurs after phagocy-tosis by DCs of apoptotic, but not of necrotic, Fluinfected cells.45 Similarly, Russo46 and Henry,47

showed that phagocytosis of apoptotic cells resultsin presentation of antigens expressed in the dyingcells, although cross presentation was not formallydemonstrated in these studies. Whether or notuptake of necrotic cells results in efficient crosspresentation is still debated. In contrast to theresults obtained with Flu, phagocytosis of necroticcells expressing EBV antigens by DC promotedcross presentation.48

Human tumor antigens can also induce crosspriming in vivo 49,50 and cross presentation in vitro.46

The group of Banchereau showed that DCs havingphagocytosed apoptotic tumor cells promote primingin vitro of tumor antigen-specific CTL.51 Antigen-specific cross presentation in vitro was also shownafter DC-sensitization with tumor cell lysates52 andexosomes. Exosomes are small membrane vesiclessecreted by both DCs53,54 and different tumor celllines.55 Tumor cell-derived exosomes contain tumor

antigens and heat shock proteins. After uptake byDC, tumor-derived exosomes, cross present tumorantigens to specific T lymphocytes in vitro and invivo. Finally, phagocytosis of antigens under other‘forms’ i.e. immune complexes,56 liposomes57 andbacteria,58 also results in efficient cross presentation.

Interestingly, receptors for phagocytosis often alsoaffect DC maturation. The effect of apoptotic versusnecrotic cells on DC maturation remains unclear.On one hand, it was shown that necrotic, but notapoptotic cells, induced DC maturation.59,60 Otherreports, however, suggested that this may be due tomycoplasma released upon induction of necrosis61

or showed that apoptotic cells may also induce DCmaturation.62 Fc receptor (FcR) engagement onDCs allows both efficient internalization and crosspresentation, but also produces DC maturation, inmouse and human DCs.56,63 Similarly, phagocytosisof bacteria58 or yeast, induces DC maturation, andeven polarises DCs towards induction of qualitativelydifferent T cell responses (Th1 versus Th2). Thus,the receptors involved in phagocytosis also affectDC differentiation to generate specific adaptativeimmune responses.

The identity of the APC responsible for crosspriming in vivo was unclear until, very recently, DCswere directly shown to be the main cross primingAPC. Indeed, two groups have now shown directlythat the actual antigen cross presenting cells in thedraining lymph nodes were DCs.64,65 Whether or notcross presentation in vitro is a specific DC-attribute isalso still unclear. In spite of many initial reports usingmacrophages, several recent papers showed that crosspresentation is restricted to DCs. Phagocytosis of Fluinfected apoptotic cells in macrophages, in contrastto DCs, does not result in cross presentation.45

Similarly, cross presentation after FcγR-mediatedinternalization of IgG-complexed antigens,56 orof antigen-expressing bacteria,58 resulted in crosspresentation in DCs, but not in macrophages. Theseresults suggest that after internalization antigens arehandled differently in both cell types.

Intracellular cross presentation pathways

How then are antigens targeted to the MHC class Ipresentation pathway after phagocytosis? Pioneeringwork in macrophages, suggested the existence oftwo cross presentation pathways, one using theendocytic pathway, and the other one using theER as the primary sites of peptide loading.14,66,67

On one hand, bacterial antigens did not require

376


newly synthesized MHC class I molecules for crosspresentation, suggesting that critical steps in thisprocess occurred within the endocytic pathway.68

Thus, in macrophages, bacterial antigens areprobably degraded within phagolysosomes intoantigenic peptides, which may eventually be loadedonto recycling MHC class I molecules present inthese compartments. On the other hand, crosspresentation after latex bead coupled antigenphagocytosis or induction of macropinocytosisin macrophages, was insensitive to inhibitors oflysosomal pH, but required TAP transporters andwas blocked by inhibitors of the proteasome. Theseresults suggest that antigens may be delivered to thecytosol for proteasomal degradation and MHC classI loading in the ER.35–37 These two intracellularpathways for cross presentation may very well accountfor the TAP-dependent and TAP-independent crosspriming routes defined in vivo and discussed above.

In contrast to macrophages, in DCs bothmacropinocytosis and transport to the cytosolare constitutive.38 Antigen export from endosomesto the cytosol in DCs occurs through a uniquemembrane transport pathway that allows delivery ofinternalized antigen into the cytosol.69 Endosomesto cytosol transport is selective for internalizedmolecules (endo-lysosomal residents like cathepsinD and β-hexosaminidase, are not delivered to thecytosol) and dependent on the size of the exportedantigens (antigens of 500 kDa and more are notefficiently exported).69 Nevertheless, immatureDCs also bear abundant MHC class I moleculesin endocytic compartments and these moleculesare re-distributed to the plasma membrane uponmaturation. Thus, MHC class I peptide loading mayoccur either directly in endosomes, or, in the ER,after export of antigens to the cytosol for degradationby the proteasome and transport of the peptides byTAP transporters. The precise nature of this transportsystem, which appears to operate in phagosomes andin other endocytic compartments in DCs, remains tobe elucidated.

If we try to put together the in vivo and in vitroresults obtained over the last few years, it is temptingto speculate that the most common in vivo crosspriming pathway, the TAP-dependent one, requiresDC-mediated presentation of MHC class I epitopesloaded in the ER after antigen uptake and transfer tothe cytosol. In the case of strong dominant epitopes,like the ones found in LCMV (for which the T cellprecursor frequency is very high), or in the caseof very high viral loads, other APCs than DCs, like

macrophages or event non-hematopoietic APCs,could initiate cytotoxic immune responses throughTAP-independent endosomal cross presentationpathways.

Conclusion

Phagocytosis certainly represents one of the mostefficient routes of antigen ingestion by APCs. Itclearly results in efficient antigen ingestion, transferto the cytosol and peptide loading on MHC classI and II molecules. Although it is most likely thatpriming of immune responses primarily depends onDCs, the exact role of macrophages as APCs involvedin the induction of tolerance should be evaluated inmore detail.

References

1. Watts C (1997) Capture and processing of exogenousantigens for presentation on MHC molecules. Annu RevImmunol 15:821–850

2. Ziegler HK, Unanue ER (1982) Decrease in macrophageantigen catabolism caused by ammonia and chloroquine isassociated with inhibition of antigen presentation to T cells.Proc Natl Acad Sci USA 79:175–178

3. Reits EA, Vos JC, Gromme M, Neefjes J (2000) The majorsubstrates for TAP in vivo are derived from newly synthesizedproteins. Nature 404:774–778

4. Schubert U, Anton LC, Gibbs J, Norbury CC, Yewdell JW,Bennink JR (2000) Rapid degradation of a large fractionof newly synthesized proteins by proteasomes. Nature404:770–774

5. Pamer E, Cresswell P (1998) Mechanisms of MHC class I-restricted antigen processing. Annu Rev Immunol 16:323–358

6. York IA, Goldberg AL, Mo XY, Rock KL (1999) Proteolysisand class I major histocompatibility complex antigen presen-tation. Immunol Rev 172:49–66

7. Paz P, Brouwenstijn N, Perry R, Shastri N (1999) Discrete pro-teolytic intermediates in the MHC class I antigen processingpathway and MHC I-dependent peptide trimming in the ER.Immunity 11:241–251

8. Brouwenstijn N, Serwold T, Shastri N (2001) MHC class Imolecules can direct proteolytic cleavage of antigenic precur-sors in the endoplasmic reticulum. Immunity 15:95–104

9. Cresswell P, Bangia N, Dick T, Diedrich G (1999) The natureof the MHC class I peptide loading complex. Immunol Rev172:21–28

10. Watts C (2001) Antigen processing in the endocytic compart-ment. Curr Opin Immunol 13:26–31

11. Cresswell P (1996) Invariant chain structure and MHC class IIfunction. Cell 84:505–507

12. Kropshofer H, Hammerling GJ, Vogt AB (1999) The impactof the non-classical MHC proteins HLA-DM and HLA-DO onloading of MHC class II molecules. Immunol Rev 172:267–278

13. Alfonso C, Karlsson L (2000) Nonclassical MHC class IImolecules. Annu Rev Immunol 18:113–142

377


14. Thery C, Amigorena S (2001) The cell biology of antigenpresentation in dendritic cells. Semin Immunol (in press)

15. Ramachandra L, Harding CV (2000) Phagosomes acquirenascent and recycling class II MHC molecules but primarilyuse nascent molecules in phagocytic antigen processing.J Immunol 164:5103–5112

16. Ramachandra L, Song R, Harding CV (1999) Phagosomes arefully competent antigen-processing organelles that mediatethe formation of peptide:class II MHC complexes. J Immunol162:3263–3272

17. Delvig AA, Robinson JH (1998) Two T cell epitopes fromthe M5 protein of viable streptococcus pyogenes engagedifferent pathways of bacterial antigen processing in mousemacrophages. J Immunol 160:5267–5272

18. Reis e Sousa C, Stahl PD, Austyn JM (1993) Phagocytosis ofantigens by langerhans cells in vitro. J Exp Med 178:509–519

19. Austyn JM (1996) New insights into the mobilizationand phagocytic activity of dendritic cells. J Exp Med183:1287–1292

20. Randolph GJ, Beaulieu S, Lebecque S, Steinman RM,Muller WA (1998) Differentiation of monocytes into dendriticcells in a model of transendothelial trafficking. Science282:480–483

21. Corinti S, Medaglini D, Cavani A, Rescigno M, Pozzi G,Ricciardi CP, Girolomoni G (1999) Human dendritic cellsvery efficiently present a heterologous antigen expressed onthe surface of recombinant gram-positive bacteria to CD4+ Tlymphocytes. J Immunol 163:3029–3036

22. Svensson M, Stockinger B, Wick MJ (1997) Bone marrow-derived dendritic cells can process bacteria for MHC-I andMHC-II presentation to T cells. J Immunol 158:4229–4236

23. Matsuno K, Ezaki T, Kudo S, Uehara Y (1996) A life stageof particle-laden rat dendritic cells in vivo: their terminaldivision, active phagocytosis, and translocation from the liverto the draining lymph. J Exp Med 183:1865–1878

24. Inaba K et al. (1998) Efficient presentation of phagocytosedcellular fragments on the major histocompatibility complexclass II products of dendritic cells. J Exp Med 188:2163–2173

25. Steinman RM, Turley S, Mellman I, Inaba K (2000) Theinduction of tolerance by dendritic cells that have capturedapoptotic cells. J Exp Med 191:411–416

26. Yrlid U, Wick MJ (2000) Salmonella-induced apoptosis ofinfected macrophages results in presentation of a bacteria-encoded antigen after uptake by bystander dendritic cells.J Exp Med 191:613–624

27. Sugita M, Peters PJ, Brenner MB (2000) Pathways forlipid antigen presentation by CD1 molecules: nowhere forintracellular pathogens to hide. Traffic 1:295–300

28. Briken V, Moody DB, Porcelli SA (2000) Diversification ofCD1 proteins: sampling the lipid content of different cellularcompartments. Semin Immunol 12:517–525

29. Schaible UE, Hagens K, Fischer K, Collins HL, Kauf-mann SH (2000) Intersection of group I CD1 moleculesand mycobacteria in different intracellular compartments ofdendritic cells. J Immunol 164:4843–4852

30. Bevan MJ (1976) Cross-priming for a secondary cytotoxicresponse to minor H antigens with H-2 congenic cellswhich do not cross-react in the cytotoxic assay. J Exp Med143:1283–1288

31. Huang AY, Golumbek P, Ahmadzadeh M, Jaffee E, Pardoll D,Levitsky H (1994) Role of bone marrow-derived cells inpresenting MHC class I-restricted tumor antigens. Science264:961–965

32. Sigal LJ, Rock KL (2000) Bone marrow-derived antigen-presenting cells are required for the generation of cytotoxic

T lymphocyte responses to viruses and use transporterassociated with antigen presentation (TAP)-dependent and-independent pathways of antigen presentation. J Exp Med192:1143–1150

33. Lenz LL, Butz EA, Bevan MJ (2000) Requirements for bonemarrow-derived antigen-presenting cells in priming cytotoxicT cell responses to intracellular pathogens. J Exp Med192:1135–1142

34. Sigal LJ, Crotty S, Andino R, Rock KL (1999) Cytotoxic T-cellimmunity to virus-infected non-haematopoietic cells requirespresentation of exogenous antigen. Nature 398:77–80

35. Kovacsovics-Bankowski M, Clark K, Benacerraf B, RockKL (1993) Efficient major histocompatibility complex classI presentation of exogenous antigen upon phagocytosisby macrophages. Proc Natl Acad Sci USA 90:4942–4946

36. Kovacsovics-Bankowski M, Rock KL (1995) A phagosome-to-cytosol pathway for exogenous antigens presented on MHCclass I molecules. Science 267:243–246

37. Norbury CC, Hewlett LJ, Prescott AR, Shastri N,Watts C (1995) Class I MHC presentation of exogenoussoluble antigen via macropinocytosis in bone marrowmacrophages. Immunity 3:783–791

38. Norbury CC, Chambers BJ, Prescott AR, Ljunggren HG,Watts C (1997) Constitutive macropinocytosis allows TAP-dependent major histocompatibility complex class I presen-tation of exogenous soluble antigen by bone marrow-deriveddendritic cells. Eur J Immunol 27:280–288

39. Hart DJ (1997) Dendritic cells are unique leukocyte popu-lations which control the primary immune response. Blood90:3245–3287

40. Fadok VA, Warner ML, Bratton DL, Henson PM (1998) CD36is required for phagocytosis of apoptotic cells by humanmacrophages that use either a phosphatidylserine receptoror the vitronectin receptor (alpha v beta 3). J Immunol161:6250–6257

41. Fadok VA, Bratton DL, Rose DM, Pearson A, Ezekewitz RA,Henson PM (2000) A receptor for phosphatidylserine-specificclearance of apoptotic cells. Nature 405:85–90

42. Rubartelli A, Poggi A, Zocchi MR (1997) The selectiveengulfment of apoptotic bodies by dendritic cells is mediatedby the alpha(v)beta3 integrin and requires intracellular andextracellular calcium. Eur J Immunol 27:1893–1900

43. Albert ML, Pearce SF, Francisco LM, Sauter B, Roy P,Silverstein RL, Bhardwaj N (1998) Immature dendritic cellsphagocytose apoptotic cells via alphavbeta5 and CD36, andcross-present antigens to cytotoxic T lymphocytes. J Exp Med188:1359–1368

44. Albert ML, Kim JI, Birge RB (2000) alphavbeta5 integrinrecruits the CrkII-Dock180-rac1 complex for phagocytosis ofapoptotic cells. Nat Cell Biol 2:899–905

45. Albert ML, Sauter B, Bhardwaj N (1998) Dendritic cellsacquire antigen from apoptotic cells and induce class I-restricted CTLs. Nature 392:86–89

46. Russo V, Tanzarella S, Dalerba P, Rigatti D, Rovere P, Villa A,Bordignon C, Traversari C (2000) Dendritic cells acquirethe MAGE-3 human tumor antigen from apoptotic cells andinduce a class I-restricted T cell response. Proc Natl Acad SciUSA 97:2185–2190

47. Henry F, Bretaudeau L, Barbieux I, Meflah K, Gre-goire M (1998) Induction of antigen presentation bymacrophages after phagocytosis of tumour apoptotic cells.Res Immunol 149:673–679

48. Subklewe M, Paludan C, Tsang M, Mahnke K, Steinman R,Munz C (2001) Dendritic cells cross-present latency geneproducts from epstein-barr virus-transformed b cells and

378


expand tumor-reactive cd8(+) killer t cells. J Exp Med193:405–412

49. Ronchetti A et al. (1999) Immunogenicity of apoptotic cellsin vivo: role of antigen load, antigen-presenting cells, andcytokines. J Immunol 163:130–136

50. Henry F, Bretaudeau L, Hequet A, Barbieux I, Lieubeau B,Meflah K, Gregoire M (1999) Role of antigen-presentingcells in long-term antitumor response based on tumor-derivedapoptotic body vaccination. Pathobiology 67:306–310

51. Berard F et al. (2000) Cross-priming of naive CD8 T cellsagainst melanoma antigens using dendritic cells loaded withkilled allogeneic melanoma cells. J Exp Med 192:1535–1544

52. Fields RC, Shimizu K, Mule JJ (1998) Murine dendritic cellspulsed with whole tumor lysates mediate potent antitumorimmune responses in vitro and in vivo. Proc Natl Acad SciUSA 95:9482–9487

53. Zitvogel L, Regnault A, Lozier A, Wolfers J, Flament C, TenzaD, Ricciardi-Castagnoli P, Raposo G, Amigorena S (1998)Eradication of established murine tumors using a novel cell-free vaccine: dendritic cell-derived exosomes. Nat Med4:594–600

54. Thery C, Regnault A, Garin J, Wolfers J, Zitvogel L, Ricciardi-Castagnoli P, Raposo G, Amigorena S (1999) Molecularcharacterization of dendritic cell-derived exosomes. Selectiveaccumulation of the heat shock protein hsc73. J Cell Biol147:599–610

55. Wolfers J et al. (2001) Tumor-derived exosomes are a sourceof shared tumor rejection antigens for CTL cross-priming. NatMed (in press)

56. Regnault A et al. (1999) FcγR-mediated induction ofdendritic cell maturation and MHC class I-restricted antigenpresentation after immune complex internalization. J ExpMed 189:371–380

57. Machy P, Serre K, Leserman L (2000) Class I-restrictedpresentation of exogenous antigen acquired by Fcgammareceptor-mediated endocytosis is regulated in dendritic cells.Eur J Immunol 30:848–857

58. Rescigno M, Citterio S, Thery C, Rittig M, Medaglini D,Pozzi G, Amigorena S, Ricciardi-Castagnoli P (1998) Bacteria-induced neo-biosynthesis, stabilization, and surface expres-sion of functional class I molecules in mouse dendritic cells.Proc Natl Acad Sci USA 95:5229–5234

59. Sauter B, Albert ML, Francisco L, Larsson M, Somersan S,Bhardwaj N (2000) Consequences of cell death: exposure tonecrotic tumor cells, but not primary tissue cells or apoptoticcells, induces the maturation of immunostimulatory dendriticcells. J Exp Med 191:423–434

60. Gallucci S, Lolkema M, Matzinger P (1999) Natural ad-juvants: endogenous activators of dendritic cells. Nat Med5:1249–1255

61. Salio M, Cerundolo V, Lanzavecchia A (2000) Dendritic cellmaturation is induced by mycoplasma infection but not bynecrotic cells. Eur J Immunol 30:705–708

62. Rovere P, Vallinoto C, Bondanza A, Crosti MC, Rescigno M,Ricciardi-Castagnoli P, Rugarli C, Manfredi AA (1998)Bystander apoptosis triggers dendritic cell maturation andantigen-presenting function. J Immunol 161:4467–4471

63. Geissmann F, Launay P, Pasquier B, Lepelletier Y,Leborgne M, Lehuen A, Brousse N, Monteiro RC (2001) Asubset of human dendritic cells expresses IgA Fc receptor(CD89), which mediates internalization and activation uponcross-linking by IgA complexes. J Immunol 166:346–352

64. Pooley JL, Heath WR, Shortman K (2001) Cutting edge:intravenous soluble antigen is presented to cd4 t cells bycd8(−) dendritic cells, but cross-presented to cd8 t cells bycd8(+) dendritic cells. J Immunol 166:5327–5330

65. den Haan JM, Lehar SM, Bevan MJ (2000) CD8(+) but notCD8(−) dendritic cells cross-prime cytotoxic T cells in vivo.J Exp Med 192:1685–1696

66. Harding CV (1996) Class I MHC presentation of exogenousantigens. J Clin Immunol 16:90–96

67. Yewdell JW, Norbury CC, Bennink JR (1999) Mechanisms ofexogenous antigen presentation by MHC class I moleculesin vitro and in vivo: implications for generating CD8+ Tcell responses to infectious agents, tumors, transplants, andvaccines. Adv Immunol 73:1–77

68. Pfeifer JD, Wick MJ, Roberts RL, Findlay K, Normark SJ,Harding CV (1993) Phagocytic processing of bacterialantigens for class I MHC presentation to T cells. Nature361:359–362

69. Rodriguez A, Regnault A, Kleijmeer M, Ricciardi-Castagnoli P,Amigorena S (1999) Selective transport of internalizedantigens to the cytosol for MHC class I presentation indendritic cells. Nat Cell Biol 1:362–368

379

phagocytosis and antigen presentation

Documents