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Intranodal Interaction with Dendritic Cells Dynamically Regulates Surface Expression of the Co-stimulatory Receptor CD226 Protein on Murine T Cells*

Open AccessPublished:September 21, 2011DOI:https://doi.org/10.1074/jbc.M111.264697
      Dendritic cells (DCs) are the most potent antigen-presenting cells of the immune system. Depending on their maturation status, they prime T cells to induce adaptive immunity or tolerance. DCs express CD155, an immunoglobulin-like receptor binding CD226 present on T and natural killer (NK) cells. CD226 represents an important co-stimulator during T cell priming but also serves as an activating receptor on cytotoxic T and NK cells. Here, we report that cells of the T and NK cell lineage of CD155−/− mice express markedly elevated protein levels of CD226 compared with wild type (WT). On heterozygous CD155+/− T cells, CD226 up-regulation is half-maximal, implying an inverse gene-dosis effect. Moreover, CD226 up-regulation is independent of antigen-driven activation because it occurs already in thymocytes and naïve peripheral T cells. In vivo, neutralizing anti-CD155 antibody elicits up-regulation of CD226 on T cells demonstrating, that the observed modulation can be triggered by interrupting CD155-CD226 contacts. Adoptive transfers of WT or CD155−/− T cells into CD155−/− or WT recipients, respectively, revealed that CD226 modulation is accomplished in trans. Analysis of bone marrow chimeras showed that regulators in trans are of hematopoietic origin. We demonstrate that DCs are capable of manipulating CD226 levels on T cells in vivo but not in vitro, suggesting that the process of T cells actively scanning antigen-presenting DCs inside secondary lymphoid organs is required for CD226 modulation. Hence, a CD226 level divergent from WT may be exploited as a sensor to detect abnormal DC/T-cell cross-talk as illustrated for T cells in mice lacking CCR7.

      Introduction

      CD155 (poliovirus receptor) and its ligand CD226 (DNAX accessory molecule 1) belong to a subfamily of Ig-like receptors. CD155 is expressed on many tissue cells such as fibroblasts, epithelia, and endothelia and on a variety of hematopoietic cell types, e.g. T cells and dendritic cells (DCs)
      The abbreviations used are: DC
      dendritic cell
      CFSE
      carboxyfluorescein diacetate succinimidyl ester
      LN
      lymph node
      PLN
      peripheral LN
      popLN
      popliteal LN
      NK
      natural killer
      SLO
      secondary lymphoid organ
      SP
      single positive
      TAMRA
      carboxytetramethylrhodamine succinimidyl ester.
      (
      • Maier M.K.
      • Seth S.
      • Czeloth N.
      • Qiu Q.
      • Ravens I.
      • Kremmer E.
      • Ebel M.
      • Müller W.
      • Pabst O.
      • Förster R.
      • Bernhardt G.
      ,
      • Takai Y.
      • Miyoshi J.
      • Ikeda W.
      • Ogita H.
      ). Accordingly, CD155 is implicated in diverse cellular functions. It mediates cell-cell or cell-matrix contacts and was found to support proliferation, motility, and migration of tissue cells lacking such contacts (
      • Erickson B.M.
      • Thompson N.L.
      • Hixson D.C.
      ,
      • Ogita H.
      • Ikeda W.
      • Takai Y.
      ,
      • Takai Y.
      • Ikeda W.
      • Ogita H.
      • Rikitake Y.
      ). In addition, CD155 participates in the establishment of humoral immune responses of the gastrointestinal tract and is required for proper terminal maturation of CD8+ thymocytes (
      • Maier M.K.
      • Seth S.
      • Czeloth N.
      • Qiu Q.
      • Ravens I.
      • Kremmer E.
      • Ebel M.
      • Müller W.
      • Pabst O.
      • Förster R.
      • Bernhardt G.
      ,
      • Qiu Q.
      • Ravens I.
      • Seth S.
      • Rathinasamy A.
      • Maier M.K.
      • Davalos-Misslitz A.
      • Forster R.
      • Bernhardt G.
      ,
      • Seth S.
      • Ravens I.
      • Kremmer E.
      • Maier M.K.
      • Hadis U.
      • Hardtke S.
      • Förster R.
      • Bernhardt G.
      ). CD226 was assigned a co-stimulatory capacity for CD4+ T cells as well as CD8+ T cells and may be involved in directing naïve CD4+ T cells into the T helper 1 differentiation pathway (
      • Dardalhon V.
      • Schubart A.S.
      • Reddy J.
      • Meyers J.H.
      • Monney L.
      • Sabatos C.A.
      • Ahuja R.
      • Nguyen K.
      • Freeman G.J.
      • Greenfield E.A.
      • Sobel R.A.
      • Kuchroo V.K.
      ,
      • Gilfillan S.
      • Chan C.J.
      • Cella M.
      • Haynes N.M.
      • Rapaport A.S.
      • Boles K.S.
      • Andrews D.M.
      • Smyth M.J.
      • Colonna M.
      ,
      • Shibuya K.
      • Lanier L.L.
      • Phillips J.H.
      • Ochs H.D.
      • Shimizu K.
      • Nakayama E.
      • Nakauchi H.
      • Shibuya A.
      ,
      • Shibuya K.
      • Shirakawa J.
      • Kameyama T.
      • Honda S.
      • Tahara-Hanaoka S.
      • Miyamoto A.
      • Onodera M.
      • Sumida T.
      • Nakauchi H.
      • Miyoshi H.
      • Shibuya A.
      ,
      • Shirakawa J.
      • Shibuya K.
      • Shibuya A.
      ,
      • Shirakawa J.
      • Wang Y.
      • Tahara-Hanaoka S.
      • Honda S.
      • Shibuya K.
      • Shibuya A.
      ). Moreover, on NK cells and cytotoxic T cells CD226 contributes to killing of target cells (
      • Pende D.
      • Castriconi R.
      • Romagnani P.
      • Spaggiari G.M.
      • Marcenaro S.
      • Dondero A.
      • Lazzeri E.
      • Lasagni L.
      • Martini S.
      • Rivera P.
      • Capobianco A.
      • Moretta L.
      • Moretta A.
      • Bottino C.
      ,
      • Seth S.
      • Georgoudaki A.M.
      • Chambers B.J.
      • Qiu Q.
      • Kremmer E.
      • Maier M.K.
      • Czeloth N.
      • Ravens I.
      • Foerster R.
      • Bernhardt G.
      ,
      • Shibuya A.
      • Campbell D.
      • Hannum C.
      • Yssel H.
      • Franz-Bacon K.
      • McClanahan T.
      • Kitamura T.
      • Nicholl J.
      • Sutherland G.R.
      • Lanier L.L.
      • Phillips J.H.
      ). By interacting with CD155 on endothelia, CD226 may also contribute to transendothelial migration of monocytes (
      • Reymond N.
      • Imbert A.M.
      • Devilard E.
      • Fabre S.
      • Chabannon C.
      • Xerri L.
      • Farnarier C.
      • Cantoni C.
      • Bottino C.
      • Moretta A.
      • Dubreuil P.
      • Lopez M.
      ). Most recently, CD226 and CD155 were assigned a role in graft-versus-host disease (
      • Nabekura T.
      • Shibuya K.
      • Takenaka E.
      • Kai H.
      • Shibata K.
      • Yamashita Y.
      • Harada K.
      • Tahara-Hanaoka S.
      • Honda S.
      • Shibuya A.
      ,
      • Seth S.
      • Ravens I.
      • Lee C.W.
      • Glage S.
      • Bleich A.
      • Förster R.
      • Bernhardt G.
      • Koenecke C.
      ).
      It is well documented that CD155 is overexpressed by a variety of tumors (
      • Carlsten M.
      • Björkström N.K.
      • Norell H.
      • Bryceson Y.
      • van Hall T.
      • Baumann B.C.
      • Hanson M.
      • Schedvins K.
      • Kiessling R.
      • Ljunggren H.G.
      • Malmberg K.J.
      ,
      • Castriconi R.
      • Dondero A.
      • Corrias M.V.
      • Lanino E.
      • Pende D.
      • Moretta L.
      • Bottino C.
      • Moretta A.
      ,
      • Chan C.J.
      • Andrews D.M.
      • McLaughlin N.M.
      • Yagita H.
      • Gilfillan S.
      • Colonna M.
      • Smyth M.J.
      ,
      • El-Sherbiny Y.M.
      • Meade J.L.
      • Holmes T.D.
      • McGonagle D.
      • Mackie S.L.
      • Morgan A.W.
      • Cook G.
      • Feyler S.
      • Richards S.J.
      • Davies F.E.
      • Morgan G.J.
      • Cook G.P.
      ,
      • Masson D.
      • Jarry A.
      • Baury B.
      • Blanchardie P.
      • Laboisse C.
      • Lustenberger P.
      • Denis M.G.
      ,
      • Merrill M.K.
      • Bernhardt G.
      • Sampson J.H.
      • Wikstrand C.J.
      • Bigner D.D.
      • Gromeier M.
      ,
      • Pende D.
      • Spaggiari G.M.
      • Marcenaro S.
      • Martini S.
      • Rivera P.
      • Capobianco A.
      • Falco M.
      • Lanino E.
      • Pierri I.
      • Zambello R.
      • Bacigalupo A.
      • Mingari M.C.
      • Moretta A.
      • Moretta L.
      ,
      • Toutirais O.
      • Cabillic F.
      • Le Friec G.
      • Salot S.
      • Loyer P.
      • Le Gallo M.
      • Desille M.
      • de La Pintière C.T.
      • Daniel P.
      • Bouet F.
      • Catros V.
      ). It appears that an aberrant expression of CD155 on cancer cells correlates with metastatic potency and poor prognosis probably because CD155 increases the invasive capacity of tumor cells (
      • Enloe B.M.
      • Jay D.G.
      ,
      • Morimoto K.
      • Satoh-Yamaguchi K.
      • Hamaguchi A.
      • Inoue Y.
      • Takeuchi M.
      • Okada M.
      • Ikeda W.
      • Takai Y.
      • Imai T.
      ,
      • Nakai R.
      • Maniwa Y.
      • Tanaka Y.
      • Nishio W.
      • Yoshimura M.
      • Okita Y.
      • Ohbayashi C.
      • Satoh N.
      • Ogita H.
      • Takai Y.
      • Hayashi Y.
      ,
      • Sloan K.E.
      • Eustace B.K.
      • Stewart J.K.
      • Zehetmeier C.
      • Torella C.
      • Simeone M.
      • Roy J.E.
      • Unger C.
      • Louis D.N.
      • Ilag L.L.
      • Jay D.G.
      ,
      • Textor S.
      • Dürst M.
      • Jansen L.
      • Accardi R.
      • Tommasino M.
      • Trunk M.J.
      • Porgador A.
      • Watzl C.
      • Gissmann L.
      • Cerwenka A.
      ). However, CD155 expression also renders tumor cells more susceptible to killing by NK and cytotoxic T cells that express the activating receptor CD226 (
      • Carlsten M.
      • Björkström N.K.
      • Norell H.
      • Bryceson Y.
      • van Hall T.
      • Baumann B.C.
      • Hanson M.
      • Schedvins K.
      • Kiessling R.
      • Ljunggren H.G.
      • Malmberg K.J.
      ,
      • Castriconi R.
      • Dondero A.
      • Corrias M.V.
      • Lanino E.
      • Pende D.
      • Moretta L.
      • Bottino C.
      • Moretta A.
      ,
      • Chan C.J.
      • Andrews D.M.
      • McLaughlin N.M.
      • Yagita H.
      • Gilfillan S.
      • Colonna M.
      • Smyth M.J.
      ,
      • El-Sherbiny Y.M.
      • Meade J.L.
      • Holmes T.D.
      • McGonagle D.
      • Mackie S.L.
      • Morgan A.W.
      • Cook G.
      • Feyler S.
      • Richards S.J.
      • Davies F.E.
      • Morgan G.J.
      • Cook G.P.
      ,
      • Pende D.
      • Spaggiari G.M.
      • Marcenaro S.
      • Martini S.
      • Rivera P.
      • Capobianco A.
      • Falco M.
      • Lanino E.
      • Pierri I.
      • Zambello R.
      • Bacigalupo A.
      • Mingari M.C.
      • Moretta A.
      • Moretta L.
      ,
      • Toutirais O.
      • Cabillic F.
      • Le Friec G.
      • Salot S.
      • Loyer P.
      • Le Gallo M.
      • Desille M.
      • de La Pintière C.T.
      • Daniel P.
      • Bouet F.
      • Catros V.
      ,
      • Carlsten M.
      • Norell H.
      • Bryceson Y.T.
      • Poschke I.
      • Schedvins K.
      • Ljunggren H.G.
      • Kiessling R.
      • Malmberg K.J.
      ,
      • Lakshmikanth T.
      • Burke S.
      • Ali T.H.
      • Kimpfler S.
      • Ursini F.
      • Ruggeri L.
      • Capanni M.
      • Umansky V.
      • Paschen A.
      • Sucker A.
      • Pende D.
      • Groh V.
      • Biassoni R.
      • Höglund P.
      • Kato M.
      • Shibuya K.
      • Schadendorf D.
      • Anichini A.
      • Ferrone S.
      • Velardi A.
      • Kärre K.
      • Shibuya A.
      • Carbone E.
      • Colucci F.
      ,
      • Tahara-Hanaoka S.
      • Shibuya K.
      • Kai H.
      • Miyamoto A.
      • Morikawa Y.
      • Ohkochi N.
      • Honda S.
      • Shibuya A.
      ). Indeed, tumor growth is accelerated in mice lacking CD226 (
      • Iguchi-Manaka A.
      • Kai H.
      • Yamashita Y.
      • Shibata K.
      • Tahara-Hanaoka S.
      • Honda S.
      • Yasui T.
      • Kikutani H.
      • Shibuya K.
      • Shibuya A.
      ). Therefore, it is widely accepted that the conducive effects of CD155 on tumor spread and the concurrent drawback by stimulating NK cell activity build up a delicate balance determining growth and metastasis of several types of cancer. This view was refined by recent findings showing that tumor cells overexpressing CD155 can cause a substantial down-modulation of CD226 on NK cells (
      • El-Sherbiny Y.M.
      • Meade J.L.
      • Holmes T.D.
      • McGonagle D.
      • Mackie S.L.
      • Morgan A.W.
      • Cook G.
      • Feyler S.
      • Richards S.J.
      • Davies F.E.
      • Morgan G.J.
      • Cook G.P.
      ,
      • Carlsten M.
      • Norell H.
      • Bryceson Y.T.
      • Poschke I.
      • Schedvins K.
      • Ljunggren H.G.
      • Kiessling R.
      • Malmberg K.J.
      ) thereby probably dampening their killing efficiency. Similarly, it was observed that chronic HIV infection correlates with a down-regulation of CD226 on antigen-specific cytotoxic CD8+ T cells that may help render these cells dysfunctional (
      • Cella M.
      • Presti R.
      • Vermi W.
      • Lavender K.
      • Turnbull E.
      • Ochsenbauer-Jambor C.
      • Kappes J.C.
      • Ferrari G.
      • Kessels L.
      • Williams I.
      • McMichael A.J.
      • Haynes B.F.
      • Borrow P.
      • Colonna M.
      ).
      Here, we demonstrate that the modulation of CD226 expression on T and NK cells is part of a natural rheostat driven in trans by CD155 present on contacting cells. Thus, naïve T cells residing in a CD155-deficient environment up-regulate CD226 regardless of whether they express CD155 themselves or not. T cells isolated from CD155-deficient mice possessing high CD226 levels down-modulate the CD226 amount present on their cell surface back to wild-type (WT) levels upon transfer into WT recipients. We provide evidence that the cell type(s) expressing CD155 and capable of regulating CD226 in trans on T cells are of hematopoietic origin. We finally demonstrate that DCs modulate CD226 surface expression on T cells upon interaction within a peripheral lymph node (PLN).

      DISCUSSION

      We demonstrated that the CD226/CD155 system represents a dynamic unit where cells expressing CD155 have the capacity of regulating in trans the level of CD226 on T cells. We identified DCs to be at least partially involved in this regulation. The underlying mechanism that executes CD226 regulation on the surface of naïve T cells remains elusive. The finding that CD226 modulation requires an in vivo environment prevented classical experiments exploring the effect of diverse drugs on cellular pathways in in vitro assays. However, the rather rapid down-regulation of CD226 would be in favor of endocytosis and is reminiscent of descriptions in the literature documenting, for example, that MHC class I chain-related molecules overexpressed by cancer cells down-regulate surface-expressed NKG2D on T and NK cells with similar kinetics (4–24 h) (
      • Doubrovina E.S.
      • Doubrovin M.M.
      • Vider E.
      • Sisson R.B.
      • O'Reilly R.J.
      • Dupont B.
      • Vyas Y.M.
      ,
      • Groh V.
      • Wu J.
      • Yee C.
      • Spies T.
      ). Endocytosis was shown to be involved in this process (
      • Groh V.
      • Wu J.
      • Yee C.
      • Spies T.
      ,
      • Ogasawara K.
      • Hamerman J.A.
      • Hsin H.
      • Chikuma S.
      • Bour-Jordan H.
      • Chen T.
      • Pertel T.
      • Carnaud C.
      • Bluestone J.A.
      • Lanier L.L.
      ), but other mechanisms such as trogocytosis or receptor shedding may also contribute to receptor down-regulation. In contrast, up-regulation of CD226 proceeds slowly but at a constant rate, requiring approximately 3 days to reach a plateau characterized by the level of CD226 observed in CD155−/− T cells. It is assumed that this represents a simple receptor accumulation over time due to the absence of CD155 on cells contacting the T cells. We showed that mRNA levels coding for CD226 are unaffected in T cells of CD155−/− mice but that the total protein content as well as the amount of CD226 detectable on the cell surface are increased. This CD226 tuning in response to interaction with CD155 reflects a completely independent mechanism from that observed for T cells differentiating into follicular helper T cells where CD226 regulation occurs at the level of transcription (
      • Seth S.
      • Ravens I.
      • Kremmer E.
      • Maier M.K.
      • Hadis U.
      • Hardtke S.
      • Förster R.
      • Bernhardt G.
      ). In addition, we never observed a cell type naturally devoid of CD226 becoming CD226+ when CD155 is absent (e.g. B cells; data not shown), suggesting that CD155 can only operate on a CD226 level already existing on other cells. These findings are in line with the idea that CD226 modulation represents a post-transcriptional event. Interestingly, loss of CD226 on cytotoxic T cells of HIV-patients is also most likely accomplished at a post-transcriptional level (
      • Cella M.
      • Presti R.
      • Vermi W.
      • Lavender K.
      • Turnbull E.
      • Ochsenbauer-Jambor C.
      • Kappes J.C.
      • Ferrari G.
      • Kessels L.
      • Williams I.
      • McMichael A.J.
      • Haynes B.F.
      • Borrow P.
      • Colonna M.
      ).
      Because mAb neutralizing CD155 exerted the same effect as the CD155 knock-out, we conclude that an ongoing CD155-CD226 interaction is required to keep the CD226 expression at the level typically found in WT. Moreover, anti-CD226 mAb blocking binding to CD155 exerted no influence on CD155 levels present on DCs, T cells, or NK cells when administered in vivo (data not shown). It is therefore likely that the dynamic CD226-CD155 unit represents a one-way system where CD155 influences CD226 expression on contacting cells, whereas CD226 has no impact on CD155 levels. We could elicit spontaneous CD226 regulation in vivo not only by treatment of mice with mAb blocking the CD155-CD226 interaction but also by adoptive transfer of T cells or DCs. However, we failed to observe regulation in vitro by co-culturing DCs and T cells, indicating that a still unknown in vivo parameter is also required to accomplish modulation. Such a factor may be a biologically active compound like a cytokine. Another parameter may consist of the active migration of T cells inside the LN, enabling their recurring contact formation to DCs, processes that require a continuous rearrangement of the cytoskeleton. Interestingly, CD226 was shown to form a complex with protein 4.1G that allows T cells to connect surface-bound CD226 to the actin skeleton upon activation (
      • Ralston K.J.
      • Hird S.L.
      • Zhang X.
      • Scott J.L.
      • Jin B.
      • Thorne R.F.
      • Berndt M.C.
      • Boyd A.W.
      • Burns G.F.
      ). Similarly to our findings, down-regulation of CD226 on HIV-specific cytotoxic T cells or on NK cells in ovarian cancer patients requires a physical contact with CD155-expressing cells (
      • Carlsten M.
      • Norell H.
      • Bryceson Y.T.
      • Poschke I.
      • Schedvins K.
      • Ljunggren H.G.
      • Kiessling R.
      • Malmberg K.J.
      ,
      • Cella M.
      • Presti R.
      • Vermi W.
      • Lavender K.
      • Turnbull E.
      • Ochsenbauer-Jambor C.
      • Kappes J.C.
      • Ferrari G.
      • Kessels L.
      • Williams I.
      • McMichael A.J.
      • Haynes B.F.
      • Borrow P.
      • Colonna M.
      ). However, in these particular settings, regulation can be achieved in vitro, indicating that different minimal requirements exist for adjustment of CD226 levels on afflicted cells.
      The physiological role or consequences of increased CD226 levels on CD155-deficient T cells remain unknown. So far, there is no evidence that changed levels of CD226 expressed by naïve T cells can influence their proliferative capacity or differentiation pathways (
      • Seth S.
      • Ravens I.
      • Kremmer E.
      • Maier M.K.
      • Hadis U.
      • Hardtke S.
      • Förster R.
      • Bernhardt G.
      and this report). However, it should be noted that most of the observations using CD155−/− cells refer to the role of DCs in priming T cells and mainly addressed CD4+ T cells. Gilfillan et al. reported that transgenic CD8+ T cells (OT-I) lacking CD226 are stimulated like WT cells when DCs were used to activate them (
      • Gilfillan S.
      • Chan C.J.
      • Cella M.
      • Haynes N.M.
      • Rapaport A.S.
      • Boles K.S.
      • Andrews D.M.
      • Smyth M.J.
      • Colonna M.
      ). Intriguingly, when a nonprofessional antigen-presenting cell was used for this purpose, CD226-deficient OT-I cells were much less efficiently stimulated compared with WT. Therefore, CD226 is probably dispensable or at least functionally redundant in settings when DCs prime T cells. Considering this, it is possible that ongoing contacts between DCs and T cells permanently adjust CD226 levels on T cells to fine tune the sensitivity toward antigens presented by antigen-presenting cells other than DCs. Consequently, an immunological effect of elevated CD226 levels on T cells may become apparent only in pathways bypassing DCs as initiators of T cell responses.
      The results obtained from the analyses of bone marrow chimeric animals revealed that only cells of hematopoietic origin are capable of manipulating CD226 expression in trans on peripheral T cells or SP thymocytes. This was an unexpected finding because T cells inside the T area of SLOs make recurrent contacts with stromal cells (
      • Bajénoff M.
      • Egen J.G.
      • Koo L.Y.
      • Laugier J.P.
      • Brau F.
      • Glaichenhaus N.
      • Germain R.N.
      ). The latter are important because their dendritic network represents a guiding path for T cells quickly moving inside SLOs (
      • Worbs T.
      • Förster R.
      ). Stromal cells express CD155 (data not shown), thus providing ample opportunity for CD155-CD226 complex formation. Likewise, during negative selection, SP thymocytes contact medullary epithelial cells (
      • Peterson P.
      • Org T.
      • Rebane A.
      ). These nonhematopoietic cells also express CD155 (
      • Qiu Q.
      • Ravens I.
      • Seth S.
      • Rathinasamy A.
      • Maier M.K.
      • Davalos-Misslitz A.
      • Forster R.
      • Bernhardt G.
      ). Therefore, naïve T cells as well as SP thymocytes discriminate between CD155 expressed by various other cell types. CD226 modulation as a response to cell-cell contact may occur only when the CD155-CD226 complex is part of the synapse otherwise the presence of CD155 on the attaching cell is ignored by the T cell. Apart from this speculation, our findings document that CD226 recognizes selectively the presence of CD155 on other cells. Thus, the widespread expression pattern of CD155 is narrowed and split up into functionally relevant subpatterns depending on its diverse biological activities.
      The finding that CD226 modulation is dependent on the CD155 gene-dosis suggests that CD226 levels found on T cells reflect the extent of effective molecular CD155-CD226 interactions. The frequency of cell-cell contacts, their intensity (number of participating molecules in the synapse) as well as their duration might sum up the observed net result of CD226 expression. At any rate, the actual level of CD226 probably mirrors the history of active encounters of the cells with other cells expressing CD155. Because we can observe changes in the CD226 levels between 3 days (e.g. following mAb application in vivo), it seems likely that the CD226 status only reflects the very recent CD155-relevant cell-cell communication. Even though it is impossible to deduce from the actual level of CD226 expression the nature and frequency of cell-cell contacts, a level divergent from WT might well inform whether a T cell experienced a regular CD155 environment during the past days. Because in vivo cell-cell contacts are required for modulation and DCs are one (if not the only) cell type capable of modulating CD226 expression in a healthy mouse, a regular CD155 environment may translate into a normal contact scenario regarding DC-T cell interactions. Indeed, the CD226 levels found on T cells of CCR7−/− support such a hypothesis. Here, peripheral T cells show abnormally high CD226 expression. This can be explained by the irregular compartmentalization of the CCR7−/− SLOs where T cells are only loosely organized in T cell zones of abnormal size and location (
      • Förster R.
      • Schubel A.
      • Breitfeld D.
      • Kremmer E.
      • Renner-Müller I.
      • Wolf E.
      • Lipp M.
      ). T cell areas usually represent a DC-T cell interaction platform of utmost importance and because DCs also require CCR7 to immigrate from the periphery (
      • Ohl L.
      • Mohaupt M.
      • Czeloth N.
      • Hintzen G.
      • Kiafard Z.
      • Zwirner J.
      • Blankenstein T.
      • Henning G.
      • Förster R.
      ), it can be assumed that the frequency of DC-T contacts in CCR7−/− SLOs is well below average compared with WT. This provides a plausible explanation for the delayed primary immune response in CCR7−/− animals (
      • Förster R.
      • Schubel A.
      • Breitfeld D.
      • Kremmer E.
      • Renner-Müller I.
      • Wolf E.
      • Lipp M.
      ). In contrast, CCR7−/− thymocytes showed normal (CD8+ SP) or even lower CD226 levels (CD4+ SP). The latter findings suggest that CCR7−/− thymocytes do not suffer from a paucity of contacts with DCs despite the profound structural abnormalities of the CCR7−/− thymi.
      The results presented here demonstrate that regulation of CD226 on T cells is not an exceptional case met in cancer or infection involving only effector cells. It rather represents a natural rheostat existing already in thymocytes and naïve peripheral T cells. It is assumed that the biological effect of a CD155-driven CD226 regulation is beneficial for the immune system and its host. From this perspective, cancer cells or viruses such as HIV exploit an existing system, helping them to escape immune surveillance. It will be interesting to learn whether other receptor-ligand interactions obey similar regulatory mechanisms as described for the CD155-CD226 system. In this case, such a receptor-driven ligand balancing may represent an important general tool in controlling the density of surface-exposed proteins complementing the array of mechanisms influencing for example post-Golgi transport and receptor endocytosis. Future work will also need to address the question of why such a modulatory pathway exists already in the steady state of an unchallenged immune system.

      Acknowledgments

      We thank Oliver Pabst (Institute of Immunology, Hannover Medical School) for critically reading the manuscript and Drs. Akira and Kazuko Shibuya (Department of Immunology, University of Tsukuba, Japan) for mAb Tx42.

      REFERENCES

        • Maier M.K.
        • Seth S.
        • Czeloth N.
        • Qiu Q.
        • Ravens I.
        • Kremmer E.
        • Ebel M.
        • Müller W.
        • Pabst O.
        • Förster R.
        • Bernhardt G.
        Eur. J. Immunol. 2007; 37: 2214-2225
        • Takai Y.
        • Miyoshi J.
        • Ikeda W.
        • Ogita H.
        Nat. Rev. Mol. Cell Biol. 2008; 9: 603-615
        • Erickson B.M.
        • Thompson N.L.
        • Hixson D.C.
        Hepatology. 2006; 43: 325-334
        • Ogita H.
        • Ikeda W.
        • Takai Y.
        J. Microsc. 2008; 231: 455-465
        • Takai Y.
        • Ikeda W.
        • Ogita H.
        • Rikitake Y.
        Annu. Rev. Cell Dev. Biol. 2008; 24: 309-342
        • Qiu Q.
        • Ravens I.
        • Seth S.
        • Rathinasamy A.
        • Maier M.K.
        • Davalos-Misslitz A.
        • Forster R.
        • Bernhardt G.
        J. Immunol. 2010; 184: 1681-1689
        • Seth S.
        • Ravens I.
        • Kremmer E.
        • Maier M.K.
        • Hadis U.
        • Hardtke S.
        • Förster R.
        • Bernhardt G.
        Eur. J. Immunol. 2009; 39: 3160-3170
        • Dardalhon V.
        • Schubart A.S.
        • Reddy J.
        • Meyers J.H.
        • Monney L.
        • Sabatos C.A.
        • Ahuja R.
        • Nguyen K.
        • Freeman G.J.
        • Greenfield E.A.
        • Sobel R.A.
        • Kuchroo V.K.
        J. Immunol. 2005; 175: 1558-1565
        • Gilfillan S.
        • Chan C.J.
        • Cella M.
        • Haynes N.M.
        • Rapaport A.S.
        • Boles K.S.
        • Andrews D.M.
        • Smyth M.J.
        • Colonna M.
        J. Exp. Med. 2008; 205: 2965-2973
        • Shibuya K.
        • Lanier L.L.
        • Phillips J.H.
        • Ochs H.D.
        • Shimizu K.
        • Nakayama E.
        • Nakauchi H.
        • Shibuya A.
        Immunity. 1999; 11: 615-623
        • Shibuya K.
        • Shirakawa J.
        • Kameyama T.
        • Honda S.
        • Tahara-Hanaoka S.
        • Miyamoto A.
        • Onodera M.
        • Sumida T.
        • Nakauchi H.
        • Miyoshi H.
        • Shibuya A.
        J. Exp. Med. 2003; 198: 1829-1839
        • Shirakawa J.
        • Shibuya K.
        • Shibuya A.
        Int. Immunol. 2005; 17: 217-223
        • Shirakawa J.
        • Wang Y.
        • Tahara-Hanaoka S.
        • Honda S.
        • Shibuya K.
        • Shibuya A.
        Int. Immunol. 2006; 18: 951-957
        • Pende D.
        • Castriconi R.
        • Romagnani P.
        • Spaggiari G.M.
        • Marcenaro S.
        • Dondero A.
        • Lazzeri E.
        • Lasagni L.
        • Martini S.
        • Rivera P.
        • Capobianco A.
        • Moretta L.
        • Moretta A.
        • Bottino C.
        Blood. 2006; 107: 2030-2036
        • Seth S.
        • Georgoudaki A.M.
        • Chambers B.J.
        • Qiu Q.
        • Kremmer E.
        • Maier M.K.
        • Czeloth N.
        • Ravens I.
        • Foerster R.
        • Bernhardt G.
        J. Leukocyte Biol. 2009; 86: 91-101
        • Shibuya A.
        • Campbell D.
        • Hannum C.
        • Yssel H.
        • Franz-Bacon K.
        • McClanahan T.
        • Kitamura T.
        • Nicholl J.
        • Sutherland G.R.
        • Lanier L.L.
        • Phillips J.H.
        Immunity. 1996; 4: 573-581
        • Reymond N.
        • Imbert A.M.
        • Devilard E.
        • Fabre S.
        • Chabannon C.
        • Xerri L.
        • Farnarier C.
        • Cantoni C.
        • Bottino C.
        • Moretta A.
        • Dubreuil P.
        • Lopez M.
        J. Exp. Med. 2004; 199: 1331-1341
        • Nabekura T.
        • Shibuya K.
        • Takenaka E.
        • Kai H.
        • Shibata K.
        • Yamashita Y.
        • Harada K.
        • Tahara-Hanaoka S.
        • Honda S.
        • Shibuya A.
        Proc. Natl. Acad. Sci. U.S.A. 2010; 107: 18593-18598
        • Seth S.
        • Ravens I.
        • Lee C.W.
        • Glage S.
        • Bleich A.
        • Förster R.
        • Bernhardt G.
        • Koenecke C.
        Proc. Natl. Acad. Sci. U.S.A. 2011; 108: E32-E33
        • Carlsten M.
        • Björkström N.K.
        • Norell H.
        • Bryceson Y.
        • van Hall T.
        • Baumann B.C.
        • Hanson M.
        • Schedvins K.
        • Kiessling R.
        • Ljunggren H.G.
        • Malmberg K.J.
        Cancer Res. 2007; 67: 1317-1325
        • Castriconi R.
        • Dondero A.
        • Corrias M.V.
        • Lanino E.
        • Pende D.
        • Moretta L.
        • Bottino C.
        • Moretta A.
        Cancer Res. 2004; 64: 9180-9184
        • Chan C.J.
        • Andrews D.M.
        • McLaughlin N.M.
        • Yagita H.
        • Gilfillan S.
        • Colonna M.
        • Smyth M.J.
        J. Immunol. 2010; 184: 902-911
        • El-Sherbiny Y.M.
        • Meade J.L.
        • Holmes T.D.
        • McGonagle D.
        • Mackie S.L.
        • Morgan A.W.
        • Cook G.
        • Feyler S.
        • Richards S.J.
        • Davies F.E.
        • Morgan G.J.
        • Cook G.P.
        Cancer Res. 2007; 67: 8444-8449
        • Masson D.
        • Jarry A.
        • Baury B.
        • Blanchardie P.
        • Laboisse C.
        • Lustenberger P.
        • Denis M.G.
        Gut. 2001; 49: 236-240
        • Merrill M.K.
        • Bernhardt G.
        • Sampson J.H.
        • Wikstrand C.J.
        • Bigner D.D.
        • Gromeier M.
        Neuro-oncology. 2004; 6: 208-217
        • Pende D.
        • Spaggiari G.M.
        • Marcenaro S.
        • Martini S.
        • Rivera P.
        • Capobianco A.
        • Falco M.
        • Lanino E.
        • Pierri I.
        • Zambello R.
        • Bacigalupo A.
        • Mingari M.C.
        • Moretta A.
        • Moretta L.
        Blood. 2005; 105: 2066-2073
        • Toutirais O.
        • Cabillic F.
        • Le Friec G.
        • Salot S.
        • Loyer P.
        • Le Gallo M.
        • Desille M.
        • de La Pintière C.T.
        • Daniel P.
        • Bouet F.
        • Catros V.
        Eur. J. Immunol. 2009; 39: 1361-1368
        • Enloe B.M.
        • Jay D.G.
        J. Neurooncol. 2011; 102: 225-235
        • Morimoto K.
        • Satoh-Yamaguchi K.
        • Hamaguchi A.
        • Inoue Y.
        • Takeuchi M.
        • Okada M.
        • Ikeda W.
        • Takai Y.
        • Imai T.
        Oncogene. 2008; 27: 264-273
        • Nakai R.
        • Maniwa Y.
        • Tanaka Y.
        • Nishio W.
        • Yoshimura M.
        • Okita Y.
        • Ohbayashi C.
        • Satoh N.
        • Ogita H.
        • Takai Y.
        • Hayashi Y.
        Cancer Sci. 2010; 101: 1326-1330
        • Sloan K.E.
        • Eustace B.K.
        • Stewart J.K.
        • Zehetmeier C.
        • Torella C.
        • Simeone M.
        • Roy J.E.
        • Unger C.
        • Louis D.N.
        • Ilag L.L.
        • Jay D.G.
        BMC Cancer. 2004; 4: 73
        • Textor S.
        • Dürst M.
        • Jansen L.
        • Accardi R.
        • Tommasino M.
        • Trunk M.J.
        • Porgador A.
        • Watzl C.
        • Gissmann L.
        • Cerwenka A.
        Int. J. Cancer. 2008; 123: 2343-2353
        • Carlsten M.
        • Norell H.
        • Bryceson Y.T.
        • Poschke I.
        • Schedvins K.
        • Ljunggren H.G.
        • Kiessling R.
        • Malmberg K.J.
        J. Immunol. 2009; 183: 4921-4930
        • Lakshmikanth T.
        • Burke S.
        • Ali T.H.
        • Kimpfler S.
        • Ursini F.
        • Ruggeri L.
        • Capanni M.
        • Umansky V.
        • Paschen A.
        • Sucker A.
        • Pende D.
        • Groh V.
        • Biassoni R.
        • Höglund P.
        • Kato M.
        • Shibuya K.
        • Schadendorf D.
        • Anichini A.
        • Ferrone S.
        • Velardi A.
        • Kärre K.
        • Shibuya A.
        • Carbone E.
        • Colucci F.
        J. Clin. Invest. 2009; 119: 1251-1263
        • Tahara-Hanaoka S.
        • Shibuya K.
        • Kai H.
        • Miyamoto A.
        • Morikawa Y.
        • Ohkochi N.
        • Honda S.
        • Shibuya A.
        Blood. 2006; 107: 1491-1496
        • Iguchi-Manaka A.
        • Kai H.
        • Yamashita Y.
        • Shibata K.
        • Tahara-Hanaoka S.
        • Honda S.
        • Yasui T.
        • Kikutani H.
        • Shibuya K.
        • Shibuya A.
        J. Exp. Med. 2008; 205: 2959-2964
        • Cella M.
        • Presti R.
        • Vermi W.
        • Lavender K.
        • Turnbull E.
        • Ochsenbauer-Jambor C.
        • Kappes J.C.
        • Ferrari G.
        • Kessels L.
        • Williams I.
        • McMichael A.J.
        • Haynes B.F.
        • Borrow P.
        • Colonna M.
        Eur. J. Immunol. 2010; 40: 949-954
        • Förster R.
        • Schubel A.
        • Breitfeld D.
        • Kremmer E.
        • Renner-Müller I.
        • Wolf E.
        • Lipp M.
        Cell. 1999; 99: 23-33
        • Ohl L.
        • Mohaupt M.
        • Czeloth N.
        • Hintzen G.
        • Kiafard Z.
        • Zwirner J.
        • Blankenstein T.
        • Henning G.
        • Förster R.
        Immunity. 2004; 21: 279-288
        • Czeloth N.
        • Bernhardt G.
        • Hofmann F.
        • Genth H.
        • Förster R.
        J. Immunol. 2005; 175: 2960-2967
        • Braun A.
        • Worbs T.
        • Moschovakis G.L.
        • Halle S.
        • Hoffmann K.
        • Bölter J.
        • Münk A.
        • Förster R.
        Nat. Immunol. 2011; 12: 879-887
        • Ravens I.
        • Seth S.
        • Förster R.
        • Bernhardt G.
        Biochem. Biophys. Res. Commun. 2003; 312: 1364-1371
        • Min B.
        • Yamane H.
        • Hu-Li J.
        • Paul W.E.
        J. Immunol. 2005; 174: 6039-6044
        • Matloubian M.
        • Lo C.G.
        • Cinamon G.
        • Lesneski M.J.
        • Xu Y.
        • Brinkmann V.
        • Allende M.L.
        • Proia R.L.
        • Cyster J.G.
        Nature. 2004; 427: 355-360
        • Hogquist K.A.
        • Baldwin T.A.
        • Jameson S.C.
        Nat. Rev. Immunol. 2005; 5: 772-782
        • Wu L.
        • Shortman K.
        Semin. Immunol. 2005; 17: 304-312
        • Davalos-Misslitz A.C.
        • Rieckenberg J.
        • Willenzon S.
        • Worbs T.
        • Kremmer E.
        • Bernhardt G.
        • Förster R.
        Eur. J. Immunol. 2007; 37: 613-622
        • Davalos-Misslitz A.C.
        • Worbs T.
        • Willenzon S.
        • Bernhardt G.
        • Förster R.
        Blood. 2007; 110: 4351-4359
        • Lei Y.
        • Ripen A.M.
        • Ishimaru N.
        • Ohigashi I.
        • Nagasawa T.
        • Jeker L.T.
        • Bösl M.R.
        • Holländer G.A.
        • Hayashi Y.
        • de Waal Malefyt R.
        • Nitta T.
        • Takahama Y.
        J. Exp. Med. 2011; 208: 383-394
        • Doubrovina E.S.
        • Doubrovin M.M.
        • Vider E.
        • Sisson R.B.
        • O'Reilly R.J.
        • Dupont B.
        • Vyas Y.M.
        J. Immunol. 2003; 171: 6891-6899
        • Groh V.
        • Wu J.
        • Yee C.
        • Spies T.
        Nature. 2002; 419: 734-738
        • Ogasawara K.
        • Hamerman J.A.
        • Hsin H.
        • Chikuma S.
        • Bour-Jordan H.
        • Chen T.
        • Pertel T.
        • Carnaud C.
        • Bluestone J.A.
        • Lanier L.L.
        Immunity. 2003; 18: 41-51
        • Ralston K.J.
        • Hird S.L.
        • Zhang X.
        • Scott J.L.
        • Jin B.
        • Thorne R.F.
        • Berndt M.C.
        • Boyd A.W.
        • Burns G.F.
        J. Biol. Chem. 2004; 279: 33816-33828
        • Bajénoff M.
        • Egen J.G.
        • Koo L.Y.
        • Laugier J.P.
        • Brau F.
        • Glaichenhaus N.
        • Germain R.N.
        Immunity. 2006; 25: 989-1001
        • Worbs T.
        • Förster R.
        Curr. Top. Microbiol. Immunol. 2009; 334: 71-105
        • Peterson P.
        • Org T.
        • Rebane A.
        Nat. Rev. Immunol. 2008; 8: 948-957