2558
`
`CORRESPONDENCE
`
`BLOOD, 25 MARCH 2010 䡠 VOLUME 115, NUMBER 12
`
`Acknowledgments: Deutsche Forschungsgemeinschaft (grant KR3473/1-1
`to C.F.), Deutsche Krebshilfe (grant 108220 to C.N., C.F.), and all
`collaborators of the European Working Group of Myelodysplastic Syndromes
`in Childhood for contributing clinical data and research material.
`Conflict-of-interest disclosure: The authors declare no competing
`financial interests.
`Contribution: C.F. and H.H. designed the study; C.F. wrote the manuscript;
`C.B. performed experiments; and H.H., E.B., M.M.v.d.H.-E., M.Z., and C.M.N.
`provided samples and clinical data.
`Correspondence: Christian Flotho, MD, Division of Pediatric Hematology-
`Oncology, Department of Pediatric and Adolescent, Medicine, University of
`Freiburg, Mathildenstr 1, 79106 Freiburg, Germany; e-mail:
`christian.flotho@uniklinik-freiburg.de.
`
`References
`1. Pasmant E, Ballerini P, Lapillonne H, et al. SPRED1 disorder and predisposi-
`tion to leukemia in children [letter]. Blood. 2009;114(5):1131.
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`2. Denayer E, de Ravel T, Legius E. Clinical and molecular aspects of RAS re-
`lated disorders. J Med Genet. 2008;45(11):695-703.
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`3. Brems H, Chmara M, Sahbatou M, et al. Germline loss-of-function mutations in
`SPRED1 cause a neurofibromatosis 1-like phenotype. Nat Genet. 2007;39(9):
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`Flotho C, Kratz CP, Niemeyer CM. Targeting RAS signaling pathways in juve-
`nile myelomonocytic leukemia. Curr Drug Targets. 2007;8(6):715-725.
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`Tartaglia M, Niemeyer CM, Fragale A, et al. Somatic mutations in PTPN11 in
`juvenile myelomonocytic leukemia, myelodysplastic syndromes and acute my-
`eloid leukemia. Nat Genet. 2003;34(2):148-150.
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`6. Schubbert S, Zenker M, Rowe SL, et al. Germline KRAS mutations cause
`Noonan syndrome. Nat Genet. 2006;38(3):331-336.
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`7. Side L, Taylor B, Cayouette M, et al. Homozygous inactivation of the NF1 gene
`in bone marrow cells from children with neurofibromatosis type 1 and malignant
`myeloid disorders. N Engl J Med. 1997;336(24):1713-1720.
`
`8. Wakioka T, Sasaki A, Kato R, et al. Spred is a Sprouty-related suppressor of
`Ras signalling. Nature. 2001;412(6847):647-651.
`
`To the editor:
`
`B cells in GVHD: friend or foe?
`
`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`We were pleased to read the recent review by Shimabukuro-
`Vornhagen et al, “The role of B cells in the pathogenesis of
`graft-versus-host disease,” which highlights the importance of
`B cells after bone marrow transplantation, as B cells have tended to
`be overlooked as a contributor to transplantation immunology.1
`This review comprehensively describes the use of the humanized
`chimeric CD20 monoclonal antibody, rituximab, for the prophy-
`laxis and treatment of acute and steroid-refractory chronic graft-
`versus-host disease (GVHD).1 Three key observations have been
`made: (1) the use of rituximab as part of pretransplantation
`conditioning results in the in vivo depletion of donor B cells after
`transplantation; (2) pretransplantation rituximab is associated with
`reduced incidence and severity of acute GVHD in a cohort of
`patients; and (3) elevated B-cell numbers in donor grafts are
`associated with the development of both acute and chronic GVHD.
`Whether B-cell depletion per se is the mechanism underlying
`reduced GVHD rates, and whether this reflects a direct role of
`B cells in stimulating allogeneic T-cell expansion and effector
`function remains unknown.
`It is important to also consider the potential nonspecific effects
`of rituximab therapy on the activation of allogeneic T cells.
`Nonspecific IgG treatment, such as high-dose intravenous immune
`globulin, can inhibit interferon-␥ (IFN-␥) responses in macro-
`phages via a Fc␥RIII-dependent mechanism, and induce natural
`killer cell–mediated antibody-dependent cellular cytotoxicity of
`dendritic cells (DCs).2,3 Apoptotic lymphocytes also have a regula-
`tory effect upon DCs, by down-regulating costimulatory molecules
`and inducing the production of the immunosuppressive cytokine
`interleukin-10 (IL-10).4,5 In GVHD, these events stimulate the
`generation and proliferation of regulatory T cells (Tregs), thus
`suppressing allogeneic T-cell activation.
`Both T and B lymphocytes play a role in tolerance induction to
`autoantigens, whereby CD4⫹ T cells regulate early allogeneic
`T-cell activation and expansion, and B cells control their differen-
`tiation into effector T cells.6 Host B cells have also been shown to
`play a protective role in GVHD, via the secretion of IL-10 after
`total body irradiation, thus inhibiting alloreactive T-cell expansion
`and subsequent acute GVHD induction.7 Donor B cells can also
`inhibit acute GVHD in a major histocompatibility complex class
`
`II– and Treg-dependent manner. Mice receiving BM from B cell–
`deficient mutant mice (B6.␮MT) developed rapid-onset acute
`GVHD, contributed by faster donor CD8⫹ T-cell engraftment and
`production of IL-2 and IFN-␥ (J.E.D., V. Watt, and D.R.S.,
`manuscript in preparation), and indirect alloantigen presentation to
`CD4⫹ T cells.8 This is supported by recent in vitro human data,
`indicating that activated B cells directly suppress allogeneic CD4⫹
`T-cell proliferation through the expansion of alloantigen-specific
`suppressor Tregs.9
`While clinical observations indicate that rituximab has a
`beneficial effect in the prophylaxis of acute GVHD, it is worth
`considering that an alternate mechanism of its action may exist
`over and above simple B-cell depletion. Furthermore, the potential
`benefit of regulatory B cells may be lost if rituximab is adopted
`wholesale into pretransplantation conditioning regimens.
`
`Joanne E. Davis
`The Haematology and Immunology Translational Research Laboratory,
`Cancer Immunology Program, The Peter MacCallum Cancer Centre,
`East Melbourne, Australia
`
`David S. Ritchie
`The Haematology and Immunology Translational Research Laboratory,
`Cancer Immunology Program, The Peter MacCallum Cancer Centre,
`East Melbourne, Australia
`
`Contribution: J.E.D. and D.R.S. co-wrote the letter.
`
`Conflict-of-interest disclosure: The authors declare no competing financial
`interests.
`
`Correspondence: Dr David S. Ritchie, Haematology and Immunology
`Translational Research Laboratory, Cancer Immunology Program, The Peter
`MacCallum Cancer Centre, St Andrews Pl, East Melbourne, Victoria, Australia
`3002; e-mail: david.ritchie@petermac.org.
`
`References
`1. Shimabukuro-Vornhagen A, Hallek MJ, Storb RF, von Bergwelt-Baildon MS.
`The role of B cells in the pathogenesis of graft-versus-host disease [review].
`Blood. 2009;114(24):4919-4927.
`2. Park-Min KH, Serbina NV, Yang W, et al. FcgammaRIII-dependent inhibition of
`interferon-gamma responses mediates suppressive effects of intravenous im-
`mune globulin. Immunity. 2007;26(1):67-78.
`Tha-In T, Metselaar HJ, Tilanus HW, et al. Intravenous immunoglobulins sup-
`press T-cell priming by modulating the bidirectional interaction between den-
`dritic cells and natural killer cells. Blood. 2007;110(9):3253-3262.
`
`3.
`
`

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`BLOOD, 25 MARCH 2010 䡠 VOLUME 115, NUMBER 12
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`CORRESPONDENCE
`
`2559
`
`4. Spisek R, Gasova Z, Bartunkova J. Maturation state of dendritic cells during
`the extracorporeal photopheresis and its relevance for the treatment of chronic
`graft-versus-host disease. Transfusion. 2006;46(1):55-65.
`5. Gatza E, Rogers CE, Clouthier SG, et al. Extracorporeal photopheresis re-
`verses experimental graft-versus host disease through regulatory T cells.
`Blood. 2008;112(4):1515-1521.
`6. Knoechel B, Lohr J, Kahn E, Abbas AK. Cutting edge: the link between lympho-
`cyte deficiency and autoimmunity: roles of endogenous T and B lymphocytes in
`tolerance. J Immunol. 2005;175(1):21-26.
`
`7. Rowe V, Banovic T, MacDonald KP, et al. Host B cells produce IL-10 following
`TBI and attenuate acute GVHD after allogeneic bone marrow transplantation.
`Blood. 2006;108(7):2485-2492.
`8. Markey KA, Banovic T, Kuns RD, et al. Conventional dendritic cells are the criti-
`cal donor APC presenting alloantigen after experimental bone marrow trans-
`plantation. Blood. 2009;113(22):5644-5649.
`9. Chen LC, Delgado JC, Jensen PE, Chen X. Direct expansion of human al-
`lospecific FoxP3⫹CD4⫹ regulatory T cells with allogeneic B cells for therapeu-
`tic application. J Immunol. 2009;183(6):4094-4102.
`
`Response
`
`Friend or foe in GVHD: a matter of targeting the right B-cell subset
`
`We thank Davis and Ritchie for their interest in our review and their
`comments. In their letter they suggest that other mechanisms than
`B-cell depletion could underlie the observed benefit of rituximab in
`graft-versus-host disease (GVHD). In addition,
`they raise the
`concern that use of rituximab could also cause harm by depleting
`regulatory B cells, which suppress allogeneic T-cell responses.
`Unfortunately, due to space constraints, we were not able to
`discuss these aspects fully in our review. We consider it unlikely
`that Fc receptor–mediated immunomodulatory effects are respon-
`sible for the therapeutic activity of rituximab in GVHD. High-dose
`intravenous immunoglobulins are of questionable use for the
`prophylaxis or treatment of GVHD.1 Furthermore, the dose of
`intravenous immunoglobulins,
`typically 500 mg/kg,
`that
`is re-
`quired to observe an immunomodulatory effect is much higher than
`the 375 mg/m2 of rituximab generally used for the treatment of
`GVHD. Several other potential mechanisms have been suggested
`to explain the effectiveness of rituximab in nonmalignant disorders
`such as autoimmune disease. For instance, recently it has been
`shown that rituximab also depletes CD20⫹ T cells, which consti-
`tute a small subpopulation of T cells with proinflammatory proper-
`ties.2 Another proposed mechanism is the formation of immune
`complexes of anti-CD20 antibodies and B cells, which act as
`decoys and sequester Fc␥ receptor–expressing effector cells such
`as macrophages.3 In addition, rituximab can also interfere with
`B-cell receptor signaling.4 Despite these potential nonspecific
`effects of rituximab, multiple independent lines of evidence both
`from experimental animal models as well as clinical data strongly
`link B lymphocytes to GVHD pathogenesis.5-7 Therefore, even
`though other mechanisms might contribute to the effectiveness of
`rituximab, we believe that the depletion of pathogenic B lympho-
`cytes themselves and not nonspecific effects of rituximab such as
`depletion of CD20⫹ T cells, Fc␥RIII-dependent immunomodula-
`tion, or the tolerogenic effect of apoptotic lymphocytes are the
`main mode of action of rituximab in GVHD.
`the use of
`We fully agree with the authors’ concern that
`rituximab also could lead to the depletion of regulatory B cells. As
`we pointed out
`in our review, certain regulatory B cells can
`suppress T-cell immune responses and some subsets of B lympho-
`cytes are associated with a reduced incidence of GVHD.6 Adminis-
`tration of rituximab therefore bears the risk of destruction of
`protective regulatory B cells and thereby might trigger or worsen
`GVHD. To our knowledge there are so far no reports of acute
`exacerbation of GVHD after administration of rituximab, indi-
`cating that
`the benefits of depleting the pathogenic B-cell
`subsets generally outweighs the harm of depleting regulatory
`B cells. Interestingly, it was reported recently that administra-
`tion of
`rituximab within the first months after stem cell
`transplantation is associated with an increased risk of cytope-
`
`nias, which possibly resulted from an autoimmune response.8
`Thus, agents that more specifically deplete the pathogenic B-cell
`subset while sparing regulatory B cells could provide superior
`results in the treatment of GVHD.
`A better characterization of human B-cell subsets and the spatial
`and temporal dynamics of their pathophysiologic contribution to
`the graft-versus-host reaction will enable us to maximize the
`benefit of B cell–targeted therapeutic approaches for the prevention
`and treatment of acute and chronic GVHD.
`
`Alexander Shimabukuro-Vornhagen
`Stem Cell Transplantation Program and Laboratory for Tumor and
`Transplantation Immunology, Department I of Internal Medicine,
`University Hospital of Cologne,
`Cologne, Germany
`
`Michael S. von Bergwelt-Baildon
`Stem Cell Transplantation Program and Laboratory for Tumor and
`Transplantation Immunology, Department I of Internal Medicine,
`University Hospital of Cologne,
`Cologne, Germany
`
`Contribution: A.S.-V. and M.S.v.B.-B. wrote the manuscript.
`
`Conflict-of-interest disclosure: The authors declare no competing financial
`interests.
`
`Correspondence: Alexander Shimabukuro-Vornhagen, Department I of
`Internal Medicine, University Hospital of Cologne, Kerpener Str 62, Cologne
`50924, Germany; e-mail: alexander.shimabukuro-vornhagen@uk-koeln.de.
`
`3.
`
`References
`1. Sokos DR, Berger M, Lazarus HM. Intravenous immunoglobulin: appropriate
`indications and uses in hematopoietic stem cell transplantation. Biol Blood Mar-
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`2. Wilk E, Witte T, Marquardt N, et al. Depletion of functionally active CD20⫹ T
`cells by rituximab treatment. Arthritis Rheum. 2009;60(12):3563-3571.
`Taylor RP, Lindorfer MA. Drug insight: the mechanism of action of rituximab in
`autoimmune disease–the immune complex decoy hypothesis. Nat Clin Pract
`Rheumatol. 2007;3(2):86-95.
`4. Kheirallah S, Caron P, Gross E, et al. Rituximab inhibits B-cell receptor signal-
`ing. Blood. 2010;115(5):985-994.
`5. Balasubramaniam T, Carter C, Lilienfeld-Toal Mv, Evans P, Gilleece MH, Cook
`G. Delayed donor B-cell reconstitution after allogeneic stem cell transplantation
`is associated with increased risk of relapse but protects from chronic graft-ver-
`sus-host disease [abstract]. Blood (ASH Annual Meeting Abstracts). 2009;
`114(22):Abstract 2228.
`6. Shimabukuro-Vornhagen A, Hallek MJ, Storb RF, von Bergwelt-Baildon MS.
`The role of B cells in the pathogenesis of graft-versus-host disease. Blood.
`2009;114(24):4919-4927.
`7. Young JS, Zhao D, Yi T, Liu H, Zeng D. Mutual activation and expansion of do-
`nor CD4⫹ T cells and B cells in transplants play a critical role in the initiation of
`chronic graft-versus-host disease [abstract]. Blood (ASH Annual Meeting Ab-
`stracts). 2009;114(22):Abstract 1342.
`8. McIver ZA, Stephens N, Naguib N, Grim A, Barrett AJ. Rituximab administra-
`tion within 6 months of allogeneic SCT carries risk of prolonged and life threat-
`ening cytopenias [abstract]. Blood (ASH Annual Meeting Abstracts). 2009;
`114(22):Abstract 793.
`
`