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`PROPERTY OF THE
`NATIONAL
`LIBRARY OF
`MEDICINE
`
`i
`F
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`
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`SAN EX 1003, Page 1
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`blood
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`JOURNAL OF
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`bioed
`
`3 DECEMBER 2009 - VOLUME 114, NUMBER 24
`
`CONTENTS
`
`COVER LEGEND
`
`B cells are central players of immoral immune responses.Al'ter binding to their
`antigens, Immoral antibodies can lead to complement activation, antibody-mediated
`cellular eytotoxicity, and Fe-mediated endocytosis. Besides producing antibodieS,
`15 cells exert several other important antibody-independent functions such as antigen
`presentation, cytokine production, and immunoregulation. Professional illustration
`by A. Y. Chen. See the article by Shimabukuro-Vornhagen et al on page 4919.
`
` “OWN“ °F INSIDE moon
`
`
`ERIC
`
`1‘"
`THE AM
`SOCIETV 0*
`HEMATOLOGV
`
`4913 Why some cells are “more equal" than others
`M. Z. Ratajczok and D.-M. Shin
`
`4914
`
`Fine-tuning targeted therapy of CML
`N. P. Shah
`
`4915
`
`Ready to analyze genetically modified human platelets
`M. Gawaz
`
`BLOOD WORK
`
`491? Blast crisis
`A. Pmsad and A. Asija
`
`by
`4919
`The role of B cells in the pathogenesis of graft-versus-host disease
`A. Shimabukuro-Vomlmgen, M. .T. Hallek, R. F. Slorb. and M. S. van Bergweit—Balldon
`
`CL'IqICAL TRIALSANDM
`OBSERVATIONS
`4928
`Evidence of serum immunoglobulin abnormalities up to 9.8 years before diflgmfis
`_
`of chronic lymphocytic leukemia: a prospective study
`l-l.-T. Tsui. N. E. Caporaso, R. A. Kyle. J. A. Kntzmann, A. Dispenziel'i. R- B- Hayes. 0* H" Mart"
`M. Albitar. P. Ghia. S. V. Rajkumar. and O. Landgren
`
`4938
`
`Nilotinib for the frontline treatment of Ph+ chronic myeloid leukemia
`G. Rosti. F. Palandri. F. Castagneni. M. Breceia. L. Levam. G. Gugliotm. A. Capucci,
`M. Cedrone, C. Fava, T. lmermesoli. G. Rage Cambrin. F. Stagno. M. Tiribeili. M- Amabile.
`s. Luatti, A. Poerio. s. Soverini. N. Testoni, o. Maninelli, o. Alimena. F. Pane. G. Saglifi- and
`M. Baccarami. for the GIMEMA CML Working Party
`
`4939 Chronic myeloid leukemia: a prospective comparison of interphasc fluorescence in
`situ hybridization and chromosome banding analysis for the definition of oomph“e
`cytogenetie response: a study of the GIMEMA CML WP
`N. Testoni, G. Manocchi, S. Lualti. M. Amabile. C. Buldazzi. M. Slacchini, M. Nanni.
`G. Rege-Cambrin. E. Giugliano, U. Giussani. E. Abruzzese, S. Karim. M. G. Grimoidi,
`A. Gozzelti, B. Crescenzi. C. Carcassi, P. Bernasconi. A. Cuneo, F. Albano, G. Fuguzza.
`A. Zaeeuria. G. Mnrtiuclli, F. Pane. (1120515. and M. Baccarani
`
`<
`am 10.3 DECEMBER 2009 - VOLUME 114, NUMBER 24
`
`vii
`
`.
`cormnuen 0N um
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`SAN EX 1003, Page 3
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`

`

`'
`.
`l
`I
`I
`n
`n
`4944 Dasatimb treatment of chronic-phase chronic myclmd leukemia. analySIS 0:.
`responses according to preexisting BCR—ABL mutations
`d
`M. c. Miiller, E. E. Cones, D.-W. Kim. B. J. Druker, P. Erhen, R. Pasquini. s. Branfor -
`T. P. Hughes, J. P. Radich, L. Ploughmim. J. Mukhopadhyay, and A. Hochhaus
`
`4954 Brief report Abnormal serum free light chain ratio in patients with multiple
`myeloma in complete remission has strong association with the presence of
`oligocloiial bands: implications for stringent complete remission definition
`C. Fernandez de Lance, M. T. Cibeira. M. Elena, J. LArostegui, L. Rosifiol. M- Rowm.
`X. Filella, .l. Yagiie, and J. Biadé
`
`4957 Brief report Classification of amyloidosis by laser microdissectioii and mass
`Spectrometry—based proteomic analysis in clinical biopsy Specimens
`I. A. Vrana, J. D. Gamez,
`B. J. Madden, J. D. Thais, H. R. Bergen Ill, and A. D0811“
`
`4960
`
`. .
`Induction ofB-ccll development in adult mice reveals the ability of bone m3!"
`produce B-la cells
`
`ow to
`
`5. Dijber, M. Hefner, M. Krcy, s. Lienenklaus, B. Roy, E. Hobeika, M. Reth. T. Buchv
`A. Waisman, K. Kietschmer. and S. Weiss
`
`4968 Undifferentiated hematopoietic cells are characterized by a genome-"lide
`undermethylation dip around the transcription start site and a liieral'Chica]
`epigenetic plasticity
`Y. s. Chung, H. J. Kim, “it-M. Kim. S.-H. Hang. K.-R. Kwon, s. An. J.-H. Park, S. Leer *1
`I.-H. Oh
`
`nd
`
`HEMATOPOIESIS AND
`STEM CELLS
`
`IMMUNOBIOLOGY
`
`__ ___ ___________ __ __ ___W
`4979
`Cell-cell cooperation at the T helper cell/mast cell immunological synapse
`N. Gaudenzio. N. Espagnolle, L. T. Mars, R. Liblau, S. Valitutti, and E. Espinosa
`
`4989
`
`ti en
`.
`B-cell follicle development remodels the conduit system and allows Somme an g
`delivery to follicular dendritic cells
`M. Bajenoff and R. N. Germain
`
`hard
`0. Blanchard-Rehner, A. s. Pulickal, c. M. .Tol—van derZijde, M. D. Shape. and A- J' P"
`
`'tro is
`-
`.
`5003 Briefreport ATG-induced eXDmssion of FOXP3 in human CD4+ T cells I“ v'
`115
`cc
`associated with T-cell activation and not the induction of FOXP3+ T regulatory
`R. Broady. J. Yu, and M. K. Levings
`
`LYMPHOID
`NEOPLASIAW
`007 Characterization eta rituximab variant with potent antiturnor activity ”gain“
`rituximab—resistant B-ccll lymphoma
`_
`.
`B’ L" L 3130- H- GEO: C- Wang. X. Zhang, L. Wu. L. Chen, Q. Tong. W. Qran- H- WM
`Y. Goo
`
`,and
`
`viii
`
`BLOOD, 3 DECEMBER 2009 - VOLUME 114. NUMBER 24
`
`GONT'"UE
`
`DONx
`
`SAN EX 1003, Page 4
`
`SAN EX 1003, Page 4
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`

`

`5016
`
`TC-PTP is required for the maintenance ofMYC-driven B~cell lymphomas
`R. M. Young. A. Polsky, and Y. RefaeIi
`
`
`
`MYELOID- _ _WNEOPLASlA
`5024 Cotreatment with panobinostat and JAKZ inhibitor TG101209 attenuates
`JAK2V617F levels and signaling and exerts synergistic cytotoxic effects against
`human myeloproliferative neoplastic cells
`Y. Wang. W. Fiskus, D. G. Chung, K. M. Buckley, K. Natarajan, R. Rao. A. Joshi, R. Balusu.
`S. Koul. J. Chen. A. Saveie, C. Ustun, A. P. Jilicila. P. Atadja, R. L. Levine, and K. N. Bhalla
`
`5034
`
`FLT3-ITD up-regulates MCL-l to promote survival of stem cells in acute myeloid
`,
`leukemia via FLTS-lTD-specific STATS activation
`.
`G. Yoshimoto, T. Miyamoto. S. Jabbarzadch-Tabrizi, T. lino, J. L. Rocnik, Y. Kikushlge. Y- My"
`T. Shima, H.1wasaki. K. Takenaka, K. Nagafuji. S.-i. Mizuno, H. Niiro. G. D. Gilliland. and
`K. Akashi
`
`PLATELETS AND-
`THHOMBOPOIESIS
`
`_ __.—.—-——-——*"
`_ _
`5044 Human platelets produced in nonobese diabetic/severe combined immumdeficient
`(NOD/SCID) mice upon transplantation of human cord blood CD34+ cells are
`functionally active in an ex vivo flow model of thrombosis
`l. I. Sailes, T. Thijs. C. Brunaud, S. F. De Meyer, J. Thys, K. Vanhoorelbeke, and H. Deckmyn
`
`THHOMBOSIS AND.
`HEMOSTASIS
`
`.
`
`_ __ fifim'
`5052 Urokinase-type plasminogen activator increases hepatocyte growth factor activity
`required for skeletal muscle regeneration
`T. H. Sisson, M.-H. Nguyen, B. Yu, M. L. Novak, R. H. Simon, and T. J. Koh
`
`% 5
`
`Inducing the tryptophan catabolie pathway, indoleamine 2,3-dioxygenase (IDO): for
`suppression of graft-versus-host disease (GVHD) lethality
`in K- Jasperson, C. Bucher, A. Panoskaltsis—Monari, A. L. Mellor, D. H. Munn, and B. R. Blazaf
`
`062
`
`5071
`
`The transfer of adaptive immunity to CMV during hematopoietic stem cell
`transplantation is dependent on the specificity and phenotype of CMV—specific
`T cells in the donor
`
`P. Scheinberg,1. J. Melenhorst, 1. M. Brenchiey. B. J. HilI, N. F. Hansel, p. K. ChanopadhyaY-
`M. Roederer, L. J. Picker. D. A. Price. A. .l. Barrett, and D. C. Douek
`
`TRANSPLANTATION
`
`VASCULAR BIOLOGY
`
`m5
`
`An impaired transendothelial migration potential of chronic lymphocytic leukemia
`(CLL) cells can be linked to ephrin-A4 expression
`E. M. Trinidad, M. Ballestcros. J. Zuloaga, A. Zapata, and L. M, Alonso—Colmenal
`
`081
`
`5091
`
`Pcrieyte recruitment daring vasculogenic tube assembly stimulates endothelial
`basement membrane matrix formation
`A. N. Stratrnan. K. M. Malone, R. D. Mahan, M. J. Davis, and G. E. Davis
`
`5102
`
`Endothelial cell ADAMTS-I3 and VWF: production,
`cleavage
`
`release, and VWF string
`
`N. A. Turner, L. Nolasco, Z. M. Rugged. and J. L. Moake
`
`x
`
`BLOOD. 3 DECEMBER 2009 - VOLUME 114, NUMBER 24
`
`CONTINUE” 0’”
`
`II
`
`SAN EX 1003, Page 5
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`

`

`OTHER DEPARTMENTS
`kw
`xvii Author Guide
`
`ib
`
`Classifieds
`
`SUBMISSION INSTRUCTIONS
`
`m A
`
`ll manuscripts, including figures, should be submitted elecironicaliy at
`http://submitbioodjoumalorg to Editor-in-Chief Cynthia Dunbar, MD; Before submitting your
`paper, review Bloadis‘ Author Guide at http://www.bloodjouma],org. If you need help during the
`submission procoss, contact the Editorial Office by phone at 202-776-0548 or via c-mail at
`editorial®hematology.org.
`
`SAN EX 1003, Page 6
`
`SAN EX 1003, Page 6
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`

`

`
`
`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`«a. A
`
`m
`
`vagina;-
`
`w- a.
`
`r."
`
`The role of B cells in the pathogenesis of graft—versuswhost disease
`
`Alexander Shimabukuro-Vornhagen,T Michael J. Hallek,1 Rainer F. Storb,2 and Michael 8. von BergweIt—Baildoni
`
`‘Laboratory for Tumor and Transplantation immunology. Stem Cell Transplantation Program and Max Eder Junior Research Group, Department I of Internal
`Medicine. University Hospital of Cologne, Cologne, Germany; and 2Fred Hutchinson Cancer Research Center, Seattle, WA
`
`Allogeneic hematopoietic stem cell trans-
`plantation is an established treatment mo-
`dality for malignant and nonmalignant
`hematologic diseases. Acute and chronic
`graft-versus-host diseases (GVHDs) are a
`major cause of morbidity and mortality
`after allogeneic stem cell transplantation.
`T cells have been identified as key play-
`ers in the graft-versus—host reaction and,
`therefore, most established drugs used
`
`against GVHD target T cells. Despite our
`knowledge on the pathogenesis of the
`GVH reaction, success of established
`therapies for prevention and treatment of
`GHVD is unsatisfactory. Recently, animal
`and human studies demonstrated that
`B cells are involved in the immunopatho-
`physiology of acute and chronic GVHD.
`Early phase clinical trials of B-cell deple-
`tion with rituximab have shown beneficial
`
`effects on both acute and chronic GVHD.
`This review summarizes the current ex-
`perimental and clinical evidence for the
`involvement of B cells in the pathogene-
`sis of acute and chronic GVHD and dis-
`cusses the clinical implications for the
`management of patients undergoing allo-
`geneic stem cell transplantation. (Blood.
`2009;114:4919-4927)
`
`Introduction
`
`Allogeneic hematopoictic stem cell transplantation (HSCT) is an
`established, potentially curative treatment modality for malignant
`and nonmalignant hematologic diseases. Graft-versus-host disease
`(GVHD)
`is a major cause of morbidity and mortality after
`allogencic HSCT and limits its wider use. Traditionally, GVHD has
`been divided into 2 forms, acute and chronic, based on the time of
`its onset. Acute GVHD has been defined as disease occurring in the
`first 100 days after transplantation, whereas chronic GVHD occurs
`after day 100. This arbitrary distinction based on the time of onset
`fails to reflect
`the different pathophysiologic mechanisms and
`clinical manifestations of acutc and chronic GVHD, however.
`Acute GVHD can occur after day 100 in patients who received a
`nonmycloablative conditioning regimen or donor lymphocyte
`infusions. In addition, GVHD with typical clinical features of
`chronic GVHD can develop well before day 100 and concurrent
`with acute GVHD. Therefore,
`the National
`institutes of Health
`consensus development project has defined new criteria for the
`diagnosis, staging, and response assessment of chronic GVHD,”
`Only a few effective therapies are currently available for the
`treatment of both forms of GVHD. The established immunosupprcs-
`sivc agents are mostly nonspecific and unfortunately associated
`with severe side effects,
`in particular the susceptibility to life
`threatening infections. Therefore, novel more selective agents are
`urgently needed.
`GVHD is an immuncemediatcd disease that results from a
`
`ecules and cell types involved in the biology of the graft-versus—
`host reaction.
`
`Because acute GVHD is thought to be mediated mainly by
`donor T cells. preventive and therapeutic treatment strategies
`have focused primarily on the inhibition of T—cell function.
`Recent animal studies suggest that B cells might also play an
`important role in the biology of GVHD. Further circumstantial
`evidence for the involvement of B cells in GVHD pathogenesis
`comes from reports of successful
`treatment of GVHD with
`B-cell depletion. The mechanisms by which B cells contribute
`to acute and chronic GVHD currently are only incompletely
`understood. Here, we provide an overview of the experimental
`and clinical evidence for a pathogenic role of B cells in GVHD
`and evaluate the implications with regard to B cclletargctcd
`therapies for the treatment of GVHD. We conclude by providing
`an outlook on novel 8 cell—specific approaches that might prove
`beneficial for the treatment of GVHD.
`
`B-cell functions in health and disease
`
`B cells are central players of the humoral immune response (Figure
`1). They are specialized in the production of antibodies and thereby
`provide a protective immune defense against bacteria, viruses, and
`harmful protein antigens such as toxins. After binding to their target
`antigen antibodies can lead to complement activation, antibody-
`complex interaction between donor and recipient adaptive immu-
`mediated cellular cytotoxicity, immune complex formation, and
`nity. Donor—derived CD4+ and CD8‘ T lymphocytes have classi—
`Fermediatcd endocytosis. Over the last decade this view, which
`cally been considered to be the main effector cells mediating
`focused on the importance of B cells for the humoral immune
`GVHD pathogenesis. In fact, removal of chlls from transplant
`response, has changed dramatically. Accumulating evidence sug-
`inocula almost completely prevents GVHD from developing,
`gests that apart from antibody production B cells contribute to the
`immune response by important antibody-independent mechanisms
`however, at the price of increased incidences of graft rejection and
`disease recurrence. In recent years, basic and clinical research has
`such as presentation of antigen, the production of cytokines and
`chemokines, as well as by acting as immunorcgulatory cells.
`provided a more detailed mechanistic understanding of the mol-
`
`
`Submitted October 21, 2008; accepted April 14, 2009. F'republished online as
`Blood First Edition paper, September 11. 2009: DOI 10.1182fblood-2003-1D-
`161638.
`
`© 2009 by The American Society of Hematology
`
`BLOOD, 3 DECEMBER 2009 - VOLUME 114, NUMBER 24
`
`4919
`
`SAN EX 1003, Page 7
`
`SAN EX 1003, Page 7
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`

`

`4920
`
`SHIMABUKURO-VOHNHAGEN et al
`
`BLOOD, 3 DECEMBER 2009 ' VOLUME 114, NUMBER 24
`
`Antibody production
`
`Cytokr'ne production
`
`
`
`Figure 1. Overview of the 8-09" functions and their
`potential relevance for GVHD. Bcells contribute to
`immune responses by antibody-mediated and antibody-
`independent mechanisms. Antibodies produced by B cells
`can lead to complement activation, antibody-dependent
`cell-mediated cytoloxicily, and Foreceptor antigen up-
`take and phagocylosis. B cells can furthermore secrete a
`large number of proinflammatory cytokines including lL—2.
`TNF—a.
`lL-G,
`|L-12, MIF, and interferon—y that activate a
`large number of immune celts such as T cells (including
`Th1? cells), macrophages, and natural killer (NK) cells
`and have been shown to be involved in regulation of the
`GVH reaction. Antigen presentation by activated B cells
`that have urn-regulated major histooompatibility complex
`and costirnulatory moiecuies such as COED and CD86
`leads to CD4+ and 008+ T—celi activation and diflerentia~
`tion. Depending on the B-oell subset and the nature of lire
`activation stimulus B lymphocytes can also act as immu-
`noregulatory cells that induce peripheral (304* and {203+
`T-cell tolerance,
`inhibit dendritic cells, and induce and
`expand regulatory Tcells. Professional illustration by
`A. Y. Chen.
`
`Antigen presentation by B cells plays a fundamental role during
`physiologic immune responses. After activation via the B-cell
`receptor (BCR) and costimulatory receptors such as CD40, B lym—
`phocytes become potent antigen-presenting cells (APCs).3 What
`sets B cells apart from other APCs is their unique ability of
`antigen-specific antigen uptake through the BCR. After binding to
`the BCR B lymphocytes internalize antigen and the internalized
`antigens are subsequently processed and presented in the context of
`major histocompatibility complex (MHC) class II as well as
`cross-presented through MHC class 1.4 Activated B cells can prime
`both CD45r and CBS+ T cells in vivo‘v5 and antigen presentation by
`B cells is important in determining the level of T—cell responses.
`This was revealed by experiments with mice that lack MHC class 11
`specifically on B cells but not on dendritic cells (DCs), which were
`characterized by impaired expansion and differentiation of T cells
`after immunization.6 In addition to presenting antigen B lympho-
`cytes can generate and secrete several cytokines and chemokines.
`They can thereby shape the type and strength of the immune
`response by activation and recruitment of other immune cells. For
`instance, analogous to the CD4+ effector Twcell subsets Harris et a]
`have identified 2 functionally distinct B—cell subsets, termed B ef-
`fectorl and B effector2 cells, that differentially regulate T—cell
`responses by the production of different sets of cytokines.7
`In several autoimmune diseases antibody—independent B—cell
`functions play an important role. More than half of the of the
`developing B cells in the bone marrow express autoreactive B—cell
`receptors (BCRS).8 These autoreactive B cells are usually deleted
`or anergized but failure of tolerance checkpoints can lead to escape
`from deletion of selfrreactive B cells and the production of
`autoantibodies and autoimmune disease. In patients with autoim-
`mune diseases such as systemic lupus erythematosus (SLE) high
`levels of B cell—trophic factors such as B celliactivating factor of
`the tumor necrosis factor (TNF) family (BAFF), also known as
`B-lymphocyte stimulator, can be found and suggest that B lympho—
`cytes participate in the autoimmune disease process. BAFF pro-
`vides survival signals to B cells and protects them from apoptosis
`by binding to 3 TNF receptor faintly members, B-ceil maturation
`antigen,
`transmembrane activator and calcium modulator and
`cyclophilin ligand interactor, and B—lymphocyte stimulator recep-
`tor 3 (BR3, also known as BAFF receptor). Overexpression of
`
`BAFF in mice leads to the development of autoimmune disease,g
`whereas neutralization of BAFF results in amelioration of autoim-
`mune pathology,10 Activated B lymphocytes secrete a variety of
`proinflammatory cytokines and chemokines,
`for example,
`interleukimo (IL—6),
`tumor necrosis factor-alpha (TNFHOL),
`interferon—gamma (IFN—y),
`IL—12, and macrophage migration
`inhibitory factor (MIF), which have been implicated in participat-
`ing in the inflammatory cascade of autoimmune pathology. In
`addition, antigen presentation by auloreactive B cells was found to
`be critical in several autoimmune disorders, for example, SLE or
`rheumatoid arthritis, and can promote autoimmune pathology
`independent of antibody productiorrr.“"3
`In contrast to their immunostimulatory characteristics, certain
`B-cell subsets can also exercise an immunomodulatory function.
`They maintain peripheral tolerance of CD4’r and CD8+ T cells by a
`variety of mechanisms, such as deletion}4 induction of anergy,15
`and cytokinevmediated suppression.16 For instance, antigen pre-
`sented by resting B cells leads to only partial activation of T cells
`and results in T—cell tolerance.17 Consistent with a tolerogenic role
`of B cells the immunologic response to tumor vaccination is
`enhanced in the absence of B cells.“2 How regulatory Bcells
`mediate suppression in not fully understood. The tolerogenic
`properties of resting B cells may be due to the low expression of
`costimulatory molecules. As outlined before, activation of B cells
`via CD40 generates antigen—presenting B cells with strong stimula-
`tory capacity. Stimulation with certain other Stimuli such as
`lipopolysaccharide or Staphylococcus cmreus Cowan I, on the other
`hand, renders B cells tolerogenic, despite inducing up-regulation of
`costimulalory molecules”19 Regulatory B cells induce tolerance
`not only by acting as tolerogenic APCs, but also by producing
`well-known immunomodulatory cytokines, foremost
`lL—lU and
`TGF—B, which can suppress T—cell responses.”-20
`In addition their direct effects on T and B cells have been
`
`shown to regulate the T-cell response indirectly by suppressing a
`broad range of other immune cells. They possess the ability to
`thwart T—cell responses by inhibiting DCsmr22 After vaccination
`DCs from B cell—deficient ptMT mice secrete higher amounts of
`IL—12 than DCs from wild—type mice. B lymphocytes can further-
`more attract regulatory T cells23 and have been shown to induce
`and expand marine and human regulatory Tcells in vitro.24'7‘5
`
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`

`BLOOD, 3 DECEMBER 2009 - VOLUME 114. NUMBER 24
`
`8 CELLS IN GVHD
`
`4921
`
`role for immunoregulatory B cells in preventing
`A functional
`autoimmune disease was
`first
`revealed in studies of murine
`
`experimental allergic encephalitis, an animal model for multiple
`sclerosis. In this model the inhibitory effect of B cells is dependent
`on IL-IO produced by a rare subpopulation of CDldhigh CD5+
`regulatory B cells.2627 The case of experimental allergic encephali-
`tis also exemplifies that B lymphocytes can exert opposing func-
`tions depending on the subset and phase of the disease course.
`Regulatory B cells protect against the development of experimental
`allergic encephalitis, whereas B—cell depletion after onset of
`disease ameliorates disease progression.27 A regulatory function of
`B cells has also been confirmed in animal models of rheumatoid
`arthritis and inflammatory bowel disease.20 Taken together, recent
`knowledge of B—eell biology has revealed that Bcetls possess
`considerable functional heterogeneity The type of Breell subsets
`involved,
`the nature, strength, and duration of the activation
`stimulus, as well as the temporospatial context determine
`whether B cells exert stimulatory or inhibitory effects on the
`immune system.
`The advent of B celialepleting monoclonal antibodies made it
`possible to study the importance ofB cells in human disease. Data
`from clinical
`trials of rituximab in patients with autoimmune
`diseases have provided important insights into the involvement of
`B cells in many aspects of the autoimmune reaction. Rituximah is a
`chimeric monoclonal antibody directed against the B cell—specific
`cluster of differentiation 20 (CD20) antigen, a transmembrane
`protein expressed on pre—B lymphocytes, and immature and mature
`B cells but not on early B-eell precursors or plasma cells. It was
`initially developed as a treatment against B—cell
`lymphomas.
`Rituximab binds to CD20 on B lymphocytes and malignant
`lymphoma and causes cell destruction by a multifactorial mecha~
`nism including antibody-dependent cell—mediated cytotoxicity,
`complement-mediated cell lysis, and direct induction of apoptosis
`of target cells. Administration of rituximab leads to a rapid and
`selective depletion of B cells that lasts for several months. Because
`plasma cells do not express CD20, serum immunoglobulin levels
`are usually not affected by treatment with rituximab.
`Based on the experimental evidence for a pathogenic role of
`B cells in autoimmune disease and reports of improvement of
`autoimmune manifestations in lymphoma patients who were treated
`with rituximab, B—eell depletion has been investigated as a
`treatment for many autoimmune diseases. Interestingly,
`it has
`shown effectiveness even in autoimmune diseases that previously
`have been thought to be mainly T cell—mediated.” Meanwhile, due
`to its effectiveness rituximab has already been approved for the
`treatment of patients with rheumatoid arthritis who do not respond
`to TNF blockade. The clinical benefit of rituximab in autoimmune
`
`disease generally correlates with the extent and duration of B—cell
`depletion. Individual clinical responses do not always correlate
`with changes in autoantihody serum levels, however. Treatment
`with rituxirnab not only depletes B cells but also down—regulates
`the expression ofimportant costimulatory molecules such as CD40
`and CD80. possibly leading to diminished Tueell activation.29
`Moreover, after rituximab treatment the number and suppressive
`function of regulatory T cells increases.30 In addition to short—term
`depletion of B lymphocytes rituximab also has beneficial long-term
`effects that persist even after recovery of the B—ccll compartment. It
`appears that rituximah reverses some of the disturbances of the
`peripheral B~cell pool and reconstitutes a normal B— and T—cell
`homeostasis in patients with autoimmune disease?”
`
`
`
`B~cell reconstitution kinetics after allogeneic
`HSCT
`
`After myeloablative allogeneic HSCT there is a long-lasting defect
`of cell-mediated immunity. A variety of factors such as the type and
`intensity of conditioning, stem cell source, drugs used for immuno-
`suppression, and occurrence of infection or GVHD influences the
`kinetics of immune recovery. B-cell reconstitution is generally
`slow and immunoglobulin levels are reduced after transplantation.
`In some patients immunoglobulin levels remain decreased for more
`than a year. Consequently, transplant recipients are at an increased
`risk of infection especially to encapsulated bacteria due to low
`levels of immunoglobulinA (IgA) and IgG2 and slower B-cell
`reconstitution is associated with higher infection rates.32 The
`reconstitution of B cells after transplantation seems to recapitulate
`B-cell ontogeny-1334 Early after transplantation there is a restricted
`B-cell repertoire, with limited BCR diversity that recovers only
`slowly.34 Furthermore, even despite quantitative normalization of
`the B—cell pool within the first year after transplantation, these
`B cells are functionally impaired.33 They exhibit a defect in the
`acquisition of somatic mutations and respond poorly to antigen,
`especially polysaccharide antigens.35
`Several factors affect the recovery of B cells after allogeneic
`stem cell transplantation. The B-cell repopulation is substantially
`influenced by the type of stem cells and the graft content.
`Peripheral blood stem cell grafts contain more B and T cells than
`bone marrow stem cell grafts. They have 3 to 18 times more B cells
`than bone marrow stem grafts resulting in a faster early B—cell
`recovery/.3537 Possibly due to stem cell mobilization with granulo—
`cyte colony-stimulating factor blood stem cell grafts also contain a
`higher propo