scholarly journals Depletion of B cells in vivo by a chimeric mouse human monoclonal antibody to CD20

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 435-445 ◽  
Author(s):  
ME Reff ◽  
K Carner ◽  
KS Chambers ◽  
PC Chinn ◽  
JE Leonard ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Chinese Hamster Ovary Cells ◽  
Human Monoclonal Antibody ◽  
B Cell Lymphoma ◽  
Target Cells ◽  
Chimeric Mouse ◽  
Variable Regions

Abstract Murine monoclonal antibody 2B8 specifically recognizes the CD20 phosphoprotein expressed on the surface of normal B lymphocytes and B- cell lymphomas. The light- and heavy-chain variable regions of 2B8 were cloned, after amplification by the polymerase chain reaction, into a cDNA expression vector that contained human IgG1 heavy chain and human kappa-light chain constant regions. High-level expression of chimeric- 2B8 antibody (C2B8) was obtained in Chinese hamster ovary cells. Purified C2B8 exhibited antigen binding affinity and human-tissue reactivity similar to the native murine antibody. In vitro studies showed the ability of C2B8 to bind human C1q, mediate complement- dependent cell lysis of human B-lymphoid cell lines, and lyse human target cells through antibody-dependent cellular cytotoxicity. Infusion of macaque cynomolgus monkeys with doses ranging from 1.6 mg/kg to 6.4 mg/kg resulted in greater than 98% depletion of peripheral blood (PB) B cells and 40% to 70% depletion of lymph node B cells. Recovery of PB B cells usually started at 2 weeks after treatment and required 60 to greater than 90 days to reach normal levels. As much as 95% depletion of B cells in peripheral lymph nodes and bone marrow was observed following weekly injections of 16.8 mg/kg antibody. No toxicity was observed in any of the animals. These results offer the possibility of using an “immunologically active” chimeric anti-CD20 antibody as an alternative approach in the treatment of B-cell lymphoma.

scholarly journals Depletion of B cells in vivo by a chimeric mouse human monoclonal antibody to CD20

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 435-445 ◽  
Author(s):  
ME Reff ◽  
K Carner ◽  
KS Chambers ◽  
PC Chinn ◽  
JE Leonard ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Chinese Hamster Ovary Cells ◽  
Human Monoclonal Antibody ◽  
B Cell Lymphoma ◽  
Target Cells ◽  
Chimeric Mouse ◽  
Variable Regions

Murine monoclonal antibody 2B8 specifically recognizes the CD20 phosphoprotein expressed on the surface of normal B lymphocytes and B- cell lymphomas. The light- and heavy-chain variable regions of 2B8 were cloned, after amplification by the polymerase chain reaction, into a cDNA expression vector that contained human IgG1 heavy chain and human kappa-light chain constant regions. High-level expression of chimeric- 2B8 antibody (C2B8) was obtained in Chinese hamster ovary cells. Purified C2B8 exhibited antigen binding affinity and human-tissue reactivity similar to the native murine antibody. In vitro studies showed the ability of C2B8 to bind human C1q, mediate complement- dependent cell lysis of human B-lymphoid cell lines, and lyse human target cells through antibody-dependent cellular cytotoxicity. Infusion of macaque cynomolgus monkeys with doses ranging from 1.6 mg/kg to 6.4 mg/kg resulted in greater than 98% depletion of peripheral blood (PB) B cells and 40% to 70% depletion of lymph node B cells. Recovery of PB B cells usually started at 2 weeks after treatment and required 60 to greater than 90 days to reach normal levels. As much as 95% depletion of B cells in peripheral lymph nodes and bone marrow was observed following weekly injections of 16.8 mg/kg antibody. No toxicity was observed in any of the animals. These results offer the possibility of using an “immunologically active” chimeric anti-CD20 antibody as an alternative approach in the treatment of B-cell lymphoma.

scholarly journals A phase Ib, open-label, dose-escalation trial of the anti-CD37 monoclonal antibody, BI 836826, in combination with gemcitabine and oxaliplatin in patients with relapsed/refractory diffuse large B-cell lymphoma

2021 ◽  
Author(s):  
Monica Balzarotti ◽  
Massimo Magagnoli ◽  
Miguel Ángel Canales ◽  
Paolo Corradini ◽  
Carlos Grande ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
B Cell ◽  
Dose Escalation ◽  
Cell Lymphoma ◽  
Human Monoclonal Antibody ◽  
B Cell Lymphoma ◽  
Chimeric Mouse ◽  
Open Label ◽  
Large B Cell Lymphoma ◽  
Large B Cell

SummaryBackground BI 836826 is a chimeric mouse–human monoclonal antibody directed against human CD37, a transmembrane protein expressed on mature B lymphocytes. This open-label, phase I dose-escalation trial (NCT02624492) was conducted to determine the maximum tolerated dose (MTD), safety/tolerability, and preliminary efficacy of BI 836826 in combination with gemcitabine and oxaliplatin in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL). Methods Eligible patients received intravenous infusions of BI 836826 on day 8 and gemcitabine 1000 mg/m2 plus oxaliplatin 100 mg/m2 on day 1, for up to six 14-day treatment cycles. Dose escalation followed the standard 3 + 3 design. Results Of 21 treated patients, 17 had relapsed/refractory DLBCL and four had follicular lymphoma transformed to DLBCL. BI 836826 dosing started at 25 mg and proceeded through 50 mg and 100 mg. Two dose-limiting toxicities (DLTs) occurred during cycle 1, both grade 4 thrombocytopenia lasting > 7 days, affecting 1/6 evaluable patients (17%) in both the 50 mg and 100 mg cohorts. Due to early termination of the study, the MTD was not determined. The most common adverse events related to BI 836826 treatment were neutropenia (52%), thrombocytopenia (48%), and anemia (48%). Eight patients (38%) experienced BI 836826-related infusion-related reactions (two grade 3). Overall objective response rate was 38%, including two patients (10%) with complete remission and six patients (29%) with partial remission. Conclusions BI 836826 in combination with GemOx was generally well tolerated but did not exceed the MTD at doses up to 100 mg given every 14 days.

scholarly journals FRI0111 TOCILIZUMAB MAY INDUCE SECONDARY HYPOGAMMAGLOBULINAEMIA. A RETROSPECTIVE CASE SERIES OF 42 PATIENTS

2020 ◽  
Vol 79 (Suppl 1) ◽  
pp. 636.2-636
Author(s):  
F. Vílchez-Oya ◽  
A. Pros ◽  
I. Carrión Barberà ◽  
J. A. Meraz Ostiz ◽  
T. C. Salman Monte ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
B Cells ◽  
B Cell ◽  
Interleukin 6 ◽  
Human Monoclonal Antibody ◽  
Case Series ◽  
Infection Risk ◽  
Immunoglobulin Levels ◽  
Igg Level

Background:Tocilizumab (TCZ) is a recombinant humanized, anti-human monoclonal antibody of the immunoglobulin G1ksubclass directed against soluble and membrane-bound interleukin 6 receptors (IL-6R) [1].Interleukin-6 (IL-6) has a pleiotropic effect on inflammation, immune response, and hematopoiesis. When it was first identified, it was named as B-cell-stimulating factor 2 (BSF-2) according to its ability to induce immunoglobulin production in Epstein-Barr virus-transformed B-cell lines or in Staphylococcus aureus Cowan 1-stimulated B cells [2-4].Nowadays, it is known that IL-6 controls the survival, population expansion and maturation of B cells and plasmablasts. In that way, the regulation of Blimp-1 by STAT3 is linked to antibody secretion and is associated with long-lived plasma cells that produce large amounts of immunoglobulin. Furthermore, the ability of IL-6 to promote humoral immunity has been linked to its effects on follicular helper T cells where they promote B cell proliferation and immunoglobulin class switching [5].Objectives:Hypogammaglobulinaemia is a known complication of some immunosuppressive drugs, not previously described in patients who received therapy with monoclonal antibody against the IL-6R. We aimed to analyzed the prevalence of hypogammaglobulinaemia in our series of patients treated with tocilizumab after a carefully diagnostic workup which ruled out other causes and analyzed whether is associated with a higher risk of infection.Methods:We conducted a retrospective review from 2010 to 2019 of forty-two patients affected with a rheumatic disease and treated with TCZ at our centre. In those patients in whom we had no record of immunoglobulin levels, we determined them in the blood analysis performed by usual clinical practice.Results:42 patients were identified, from whom 38 had rheumatoid arthritis. A 31% had immunoglobulin levels prior to starting treatment with TCZ but no one had hypogammaglobulinaemia. 2 patients were excluded due to their underlying disease could justify the IgG level abnormalities. During the treatment’s follow-up, we identified that a 30% of the patients (12/40) had hypogammaglobulinaemia. Of those patients in whom immunoglobulin levels had been determined prior to starting treatment with TCZ, a 36.3% of them (4/11) developed hypogammaglobulinaemia during the follow-up. From the series, we observed a statistical significance tendency (p=0.0057) for infection risk in those patients with hypogammaglobulinaemia in contrast to those with normal IgG level (41.5% vs 14.3%, respectively).Conclusion:Secondary hypogammaglobulinaemia may occurs in patients receiving anti-IL6 agents such as tocilizumab and this could be associated with an increasing infection risk. The prevalence is not precisely known, in part because measurement of IgG prior to or during the treatment has not been a standard of care. No medical data have been previously disclosed about this possible adverse effect of anti-interleukin-6 agents. Nevertheless, ideally randomized trials are needed to assess this initial hypothesis.References:[1]Sheppard M, Laskou F, Stapleton PP, Hadavi S, Dasgupta B. Tocilizumab (Actemra). Hum Vaccin Immunother. 2017;13(9):1972–1988.[2]Tanaka T, Kishimoto T. The biology and medical implications of interleukin-6. Cancer Immunol Res. 2014;2(4):288–294.[3]Tanaka T, Narazaki M, Kishimoto T. IL-6 in inflammation, immunity, and disease. Cold Spring Harb Perspect Biol. 2014;6(10):a016295. Published 2014 Sep 4.[4]Kishimoto T. Interleukin-6: discovery of a pleiotropic cytokine. Arthritis Res Ther. 2006;8 Suppl 2(Suppl 2):S2.[5]Hunter CA, Jones SA. IL-6 as a keystone cytokine in health and disease [published correction appears in Nat Immunol. 2017 Oct 18;18(11):1271]. Nat Immunol. 2015;16(5):448–457.Disclosure of Interests:Francisco Vílchez-Oya: None declared, Ana Pros: None declared, Irene Carrión Barberà Grant/research support from: I received a grant from the Spanish Rheumatology Foundation (FER) and laboratories KERN PHARMA for a brief stay abroad., Juan Antonio Meraz Ostiz: None declared, Tarek Carlos Salman Monte: None declared, Carolina Perez-Garcia: None declared

scholarly journals Ki-B5: a monoclonal antibody unrelated to CD45 recognizes normal and neoplastic human B cells in routine paraffin sections

Blood ◽  
1991 ◽  
Vol 77 (4) ◽  
pp. 809-817 ◽  
Author(s):  
ML Hansmann ◽  
HH Wacker ◽  
J Gralla ◽  
H Lumbeck ◽  
M Kossmahl ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Protein Fractions ◽  
Paraffin Sections ◽  
Human B Cells ◽  
Normal Human

In the search for immunoreagents appropriate for the histopathologic diagnosis of malignant B-cell lymphomas in routinely processed paraffin sections, a new monoclonal antibody, Ki-B5, was generated using a high- grade B-cell lymphoma as the immunogene. Ki-B5 is a mouse IgG1/kappa that recognizes five protein fractions of about 84, 82, 55, 48, and 27 Kd after biosynthetic radiolabeling and immunoprecipitation. Protein fractions with the molecular weights of approximately 84 and 82 Kd were expressed on the cell surface and show that Ki-B5 is probably unrelated to CD45. It was possible through electron microscopy to visualize the membrane-bound portion of Ki-B5. Extensive immunohistologic studies on normal human tissue and various neoplasias demonstrated the high specificity of Ki-B5 to normal human B cells and a minor subgroup of plasma cells. Except for ML-2, which is a myelomonocytic human cell line, Ki-B5 exclusively recognized the B-cell lineage, including EB-3, BALL-1, and NALM-1. All carcinomas, sarcomas, and malignant melanomas tested with Ki-B5 were negative. Although normal granulocytes and monocytes were constantly negative, three of eight myelomonocytic leukemias coreacted with this antibody. Eight of the 57 T-cell lymphomas studied were positive to Ki-B5. Five were classified as lymphoblastic, two represented T8-CLL, and one was classified as immunoblastic T-cell lymphoma. Only 3 of 126 cases of B-cell lymphoma, including rare types not considered in the current classifications, were negative to Ki-B5. Plasmacytomas were also negative, except for one case. Irrespective of the cases of lymphoblastic lymphoma and plasmacytoma, Ki-B5 represents a new monoclonal antibody appropriate for the diagnosis and immunophenotyping of malignant lymphomas in routinely processed paraffin sections.

Targeting, dosimetry, and radioimmunotherapy of B-cell lymphomas with iodine-131-labeled LL2 monoclonal antibody.

1991 ◽  
Vol 9 (4) ◽  
pp. 548-564 ◽  
Author(s):  
D M Goldenberg ◽  
J A Horowitz ◽  
R M Sharkey ◽  
T C Hall ◽  
S Murthy ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
B Cells ◽  
B Cell ◽  
B Cell Lymphoma ◽  
Average Distribution ◽  
Iodine 131 ◽  
Total Body ◽  
Human Antimouse Antibody ◽  
Therapeutic Doses ◽  
Body Clearance

Sixteen patients with non-Hodgkin's lymphoma were infused with 6.2 to 58.2 mCi (0.2 to 3.9 mg) doses of radioactive iodine (131I)-labeled LL2 immunoglobulin G (IgG) or F(ab')2, in order to study antibody distribution, pharmacokinetics, dosimetry, toxicity, tumor targeting, and therapy. LL2 is a murine IgG2a monoclonal antibody (MAb) reactive with B cells and non-Hodgkin's B-cell lymphoma. In a series of five assessable therapy patients, doses as small as 30 mCi 131I-LL2 IgG or F(ab')2 resulted in tumor responses (two partial remissions, two mixed and minor responses, and one no response), while one patient receiving diagnostic doses as low as 6.2 mCi showed a partial remission for 1 year and a complete remission after a second low radiation dose. No acute toxicities were noted, and only myelotoxicity accompanied therapeutic doses, with grade IV marrow toxicity seen in three of seven patients receiving total doses of about 50 mCi. Dosimetry calculations showed spleen and tumor dose rules of about 4.6 cGy/mCi, which was three to four times the dose to other organs. Despite the administration of relatively low doses of LL2 (0.2 to 3.9 mg), 82% of 60 known extrasplenic lymphoma sites were imaged. Serum clearance showed an average distribution half-life (T1/2) of 2.1 hours and an elimination T1/2 of 32.0 hours. The average total-body clearance T1/2 was 43 to 45 hours. LL2's antigenic target does not appear to be shed in high amounts into the circulation. Three of eight patients having at least two injections showed a human antimouse antibody response. These patients may have been presensitized to animal protein. An interesting observation in this study was the marked drop in circulating B lymphocytes after the administration of radioiodinated LL2 or anticarcinoembryonic antigen MAbs, suggesting that this is a nonspecific radiation effect and not necessarily related to the binding of MAb to normal B cells.

scholarly journals Ki-B5: a monoclonal antibody unrelated to CD45 recognizes normal and neoplastic human B cells in routine paraffin sections

Blood ◽  
1991 ◽  
Vol 77 (4) ◽  
pp. 809-817 ◽  
Author(s):  
ML Hansmann ◽  
HH Wacker ◽  
J Gralla ◽  
H Lumbeck ◽  
M Kossmahl ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Protein Fractions ◽  
Paraffin Sections ◽  
Human B Cells ◽  
Normal Human

Abstract In the search for immunoreagents appropriate for the histopathologic diagnosis of malignant B-cell lymphomas in routinely processed paraffin sections, a new monoclonal antibody, Ki-B5, was generated using a high- grade B-cell lymphoma as the immunogene. Ki-B5 is a mouse IgG1/kappa that recognizes five protein fractions of about 84, 82, 55, 48, and 27 Kd after biosynthetic radiolabeling and immunoprecipitation. Protein fractions with the molecular weights of approximately 84 and 82 Kd were expressed on the cell surface and show that Ki-B5 is probably unrelated to CD45. It was possible through electron microscopy to visualize the membrane-bound portion of Ki-B5. Extensive immunohistologic studies on normal human tissue and various neoplasias demonstrated the high specificity of Ki-B5 to normal human B cells and a minor subgroup of plasma cells. Except for ML-2, which is a myelomonocytic human cell line, Ki-B5 exclusively recognized the B-cell lineage, including EB-3, BALL-1, and NALM-1. All carcinomas, sarcomas, and malignant melanomas tested with Ki-B5 were negative. Although normal granulocytes and monocytes were constantly negative, three of eight myelomonocytic leukemias coreacted with this antibody. Eight of the 57 T-cell lymphomas studied were positive to Ki-B5. Five were classified as lymphoblastic, two represented T8-CLL, and one was classified as immunoblastic T-cell lymphoma. Only 3 of 126 cases of B-cell lymphoma, including rare types not considered in the current classifications, were negative to Ki-B5. Plasmacytomas were also negative, except for one case. Irrespective of the cases of lymphoblastic lymphoma and plasmacytoma, Ki-B5 represents a new monoclonal antibody appropriate for the diagnosis and immunophenotyping of malignant lymphomas in routinely processed paraffin sections.

scholarly journals Production and Characterization of a Set of Mouse-Human Chimeric Immunoglobulin G (IgG) Subclass and IgA Monoclonal Antibodies with Identical Variable Regions Specific forPseudomonas aeruginosa Serogroup O6 Lipopolysaccharide

1998 ◽  
Vol 66 (9) ◽  
pp. 4137-4142 ◽  
Author(s):  
Michael J. Preston ◽  
A. Alev Gerçeker ◽  
Mitchell E. Reff ◽  
Gerald B. Pier
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Heavy Chain ◽  
Light Chain ◽  
Chimeric Mouse ◽  
Constant Region ◽  
Opsonic Activity ◽  
Variable Regions ◽  
Heavy Chain Constant Region ◽  
Complement Deposition

ABSTRACT The heavy- and light-chain variable regions from a murine monoclonal antibody that recognize Pseudomonas aeruginosaserogroup O6 lipopolysaccharide (LPS) were used to generate a series of chimeric mouse-human monoclonal antibodies with identical variable regions. The murine variable-region gene segments were cloned into an immunoglobulin (Ig) cDNA expression vector that contained the human kappa light-chain and IgG1 constant regions. The IgG1 heavy-chain constant region was then replaced with the human IgG2, IgG3, IgG4, or IgA1 heavy-chain constant region. The five different expression vectors were transfected into Chinese hamster ovary cells for antibody production. The chimeric antibodies exhibited immunoreactivity and affinity similar to that of the parental murine IgG antibody toward whole cells of a serogroup O6 strain. In vitro complement deposition assays demonstrated that the chimeric IgG4 and IgA antibodies did not mediate the deposition of complement component C3 onto the surface of either purified LPS or whole bacteria. The chimeric IgG1 and IgG3 antibodies were similar in their ability to deposit C3 onto the surface of both bacteria and LPS, while IgG2 antibody was more effective at depositing C3 onto the surface of bacteria than onto purified LPS. The pattern of opsonophagocytic activity of the chimeric monoclonal antibodies was similar to that of complement deposition onto bacterial cells in that the chimeric IgG1 and IgG3 had the highest opsonic activity. Although IgG2 deposited more C3 onto the bacterial surface than did IgG4 or IgA, all three of these isotypes had low opsonic activity against the serogroup O6 target strain. This series of related antibodies will help reveal functional differences in efficacy among protective antibodies to P. aeruginosa and will be critical for defining the optimal formulation of either a vaccine for active immunization or a polyclonal intravenous IgG or monoclonal antibody cocktail for passive immunotherapy.

Activation-Induced Cytidine Deaminase Expression in Diffuse Large B-Cell Lymphoma With a Paracortical Growth Pattern: A Lymphoma of Possible Interfollicular Large B-Cell Origin

2010 ◽  
Vol 134 (3) ◽  
pp. 449-456
Author(s):  
Nadine S. Aguilera ◽  
Aaron Auerbach ◽  
Carol L. Barekman ◽  
Jack Lichy ◽  
Susan L. Abbondanzo
Keyword(s):  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Cell Lymphoma ◽  
Cytidine Deaminase ◽  
B Cell Lymphoma ◽  
Immunoglobulin Heavy Chain ◽  
Large B Cell Lymphoma ◽  
Activation Induced Cytidine Deaminase ◽  
Large B Cell

Abstract Context.—Activation-induced cytidine deaminase, necessary for immunoglobulin somatic hypermutation and class switch recombination, is usually expressed within the follicular dendritic network but is also expressed in a population of interfollicular large B cells outside the germinal center. Objective.—To report 7 cases of diffuse large B-cell lymphoma with a distinct paracortical distribution. Expression of activation-induced cytidine deaminase, previously described in interfollicular large B cells, was evaluated. Design.—A panel of immunohistochemical markers, including double staining for activation-induced cytidine deaminase and CD20, was used to illustrate the cases. Molecular studies were performed by polymerase chain reaction in the paraffin-embedded tissue for t(14;18) chromosomal translocation and immunoglobulin heavy chain and T-cell receptor rearrangements. Results.—Patients included 3 males and 4 females ranging in age from 11 to 59 years (mean, 39 years). All specimens were lymph nodes (4 from the groin, 2 from the neck, and 1 from the axilla). Malignant lymphocytes were positive for CD20 and negative for CD5 and CD10. Staining for CD30, CD43, and BCL-2 was variable. The malignant cells showed at least focal staining with activation-induced cytidine deaminase. All cases were found to be monoclonal by immunoglobulin heavy-chain gene rearrangement or showed light-chain restriction. None of the tested cases showed t(14;18). Conclusions.—Diffuse large B-cell lymphoma with a paracortical distribution is unusual and may be a distinct morphologic variant. More study is necessary to determine the stage of B-cell development and the cell of origin of these tumors. However, activation-induced cytidine deaminase expression suggests they may arise from a putative interfollicular large B cell.

Proteome Changes Induced by Rituximab: Significance for Monoclonal Antibody Therapy of B-Cell Lymphoproliferative Disorders.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2292-2292
Author(s):  
Kathryn L. Everton ◽  
David R. Abbott ◽  
David K. Crockett ◽  
Kojo S.J. Elenitoba-Johnson ◽  
Megan S. Lim
Keyword(s):  
Monoclonal Antibody ◽  
B Cells ◽  
B Cell ◽  
Intracellular Signaling ◽  
B Cell Lymphoma ◽  
Lymphoproliferative Disorders ◽  
26S Proteasome ◽  
Differentially Expressed ◽  
Regulatory Subunit ◽  
Calcium Signal

Abstract Rituximab is a human chimeric monoclonal antibody that targets the CD20 receptor uniquely expressed on normal and malignant B-cells. While it is particularly useful for follicular lymphoma, Rituximab has recently been used for other types of B-cell proliferative disorders. Four major mechanisms have been proposed to account for the activity of Rituximab in B-cell lymphoproliferative disorders: 1) apoptosis and proliferation inhibition via intracellular signaling, 2) increased sensitivity to other chemotherapeutic drugs, 3) complement-dependent cytotoxicity (CDC), and 4) antibody-dependent cellular cytotoxicity (ADCC). A combination of all four mechanisms has also been proposed as the mechanism of action. However, the intracellular events that occur in B-cells in response to Rituximab are largely unknown. We have employed a global quantitative proteomic profiling approach to study the effects of Rituximab on a t(14;18)+ B cell lymphoma (SUDHL-4). A decrease in viability of 31.3 ± 2.9% was observed after treatment with 10μg/mL of Rituximab for 48 hours. We used isotope-coded affinity tagging (ICAT™) in combination with microcapillary liquid chromatography and tandem mass spectrometry (μLC-MS/MS) to quantitatively determine the proteomic differences between equal amounts of untreated and treated total cell lystates. Protein lysates were labeled with either heavy or light cleavable ICAT™ reagents, digested with trypsin, and purified using avidin affinity chromatography. The labeled peptides were then fractionated using off-line strong cation exchange (SCX) and each fraction was subjected to μLC-MS/MS analysis. Several proteins previously unknown to be expressed in B-cells were identified using this approach. Of the 123 positively identified proteins, 59 proteins were differentially expressed by greater than or less than 1.5 fold (25 upregulated, 34 downregulated). Analysis of differentially expressed proteins identified several functional groups, including integral membrane proteins (Integrin alpha-7 precursor), transcription factors (Zinc finger proteins 445 and 20), proteins involved in migration and adhesion (Astrotactin1), proteins associated with degradation and turnover (26S proteasome non-ATPase regulatory subunit 9), proteins affecting calcium-induced signaling (Tumor-associated calcium signal transducer 1 precursor), proteins associated with lipid rafts (Gemin7), and components of the phosphoinositol (PI4K-alpha) and NF-κB pathways (IKK-E). Our studies reveal the proteomic consequences of Rituximab administration to neoplastic B-cells, and provide novel insights into the mechanism of the drug’s efficacy in the treatment of susceptible B-cell lymphoproliferative disorders.

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