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Immunology |
1 Laboratoire d’Immunologie, 2 Laboratoire de Pharmacologie, and 3 Service d’Oncologie Médicale et Maladies du Sang, Centre Hospitalier Régional et Universitaire; 4 "Immuno-Pharmaco-Genetics of Therapeutic Antibodies" Université François Rabelais de Tours; and 5 IFR 135: Imagerie Fonctionnelles Tours, France
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ABSTRACT |
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 Top ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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RIIIa-158V and FcRIIIa-158F. The genotype homozygous for FcRIIIa-158V (VV) is associated with higher clinical response to rituximab, a chimeric anti-CD20 IgG1 used in the treatment of B lymphoproliferative malignancies. Our objective was to determine whether this genetic association relates to rituximab-dependent cytotoxicity mediated by FcRIIIa/CD16a+ cells. The number of CD16+ circulating monocytes, T cells, and natural killer (NK) cells in 54 donors was first shown to be unrelated to FCGR3A polymorphism. We then demonstrated that FcRIIIa-158V displays higher affinity for rituximab than FcRIIIa-158F by comparing rituximab concentrations inhibiting the binding of 3G8 mAb (anti-CD16) with VV NK cells and NK cells homozygous for FcRIIIa-158F (FF). VV and FF NK cells killed Daudi cells similarly after FcRIIIa engagement by saturating concentrations of rituximab or 3G8. However, the rituximab concentration resulting in 50% lysis (EC50) observed with NK cells from VV donors was 4.2 times lower than that observed with NK cells from FF donors (on average 0.00096 and 0.00402 µg/ml, respectively, P = 0.0043). Finally, the functional difference between VV and FF NK cells was restricted to rituximab concentrations weakly sensitizing CD20. This study supports the conclusion that FCGR3A genotype is associated with response to rituximab because it affects the relationship between rituximab concentration and NK cell-mediated lysis of CD20+ cells. Rituximab administration could therefore be adjusted according to FCGR3A genotype. |
INTRODUCTION |
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TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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RIIIa/CD16a, one of the low-affinity receptors for IgG Fc, is involved in antibody-dependent cell-mediated cytotoxicity (ADCC). It links IgG-sensitized target cells to FcRIIIa/CD16a-bearing cytotoxic cells, i.e., CD56dim natural killer (NK) cells, a fraction of monocyte/macrophages, and a fraction of T cells, and activates these effector cells. The FCGR3A gene, which encodes FcRIIIa, displays a functional allelic dimorphism generating allotypes with either a phenylalanine (F) or a valine (V) residue at amino acid position 158 (1
, 2)
. This residue directly interacts with the lower hinge region of IgG1, as recently shown by IgG1-FcRIII cocrystallization (3
, 4)
. Accordingly, flow cytometry studies have shown that NK cells from donors homozygous for FcRIIIa-158V (VV) bound more human IgG1 and IgG3 than did NK cells from donors homozygous for FcRIIIa-158F (FF; Refs. 1
and 2
). This difference might result from higher affinity of the FcRIIIa-158V allotype (2)
or alternatively from higher FcRIIIa membrane expression on NK cells expressing this allotype (5)
.
Rituximab (Mabthera, Rituxan) is a chimeric anti-CD20 IgG1 monoclonal antibody (mAb) consisting of human 1 and 
constant regions linked to murine variable domains (6)
. Over the past few years, rituximab has considerably modified the therapeutic strategy for B lymphoproliferative malignancies, particularly non-Hodgkin’s lymphomas (NHLs). Rituximab, alone or in combination with chemotherapy, has been shown to be effective in the treatment of both low-intermediate and high-grade NHLs (7, 8, 9, 10, 11, 12)
, although the response rate varies with the histological type, with low-grade/follicular lymphomas displaying the best response rate (8
, 10
, 11)
. Nevertheless, 30–50% of patients with low-grade NHLs exhibit no clinical response, and the actual causes of treatment failure remain largely unknown.
In vitro studies suggest that rituximab induces lymphoma cell lysis through ADCC (6
, 13)
, complement-dependent cytotoxicity (6
, 13, 14, 15, 16)
, FcRII/CD32-dependent phagocytosis (13)
, or direct signaling leading to apoptosis (17, 18, 19)
. The implication of both FcR and complement activation in the in vivo antitumor effect of rituximab against CD20+ lymphoma cell lines has been clearly demonstrated in murine models (20
, 21)
. We have recently shown an association between FCGR3A genotype and response to rituximab in previously untreated follicular NHL patients with low tumor burden (22)
. Indeed, VV patients had a higher probability of experiencing a clinical response compared with F carriers. The association between FCGR3A genotype and clinical response to rituximab has also been observed in relapsed follicular NHL patients (23)
and in Waldenström’s macroglobulinemia patients (24)
. In addition, systemic lupus erythemathosus patients with the VV or VF genotype had better B-cell depletion after rituximab treatment than FF patients (25)
. Although the genetic association does not demonstrate that the mode of action of rituximab involves FcRIIIa, we postulated that VV patients show a better response because they have a more efficient rituximab-dependent ADCC against CD20+ cells. The ADCC efficiency may depend on variability of target cells and/or effector cells. However, lymphoma cells from patients with distinct histological types expressing different levels of CD20 are equally sensitive to ADCC in the presence of rituximab (13)
. The aim of this study was therefore to investigate the influence of the FCGR3A polymorphism on rituximab-dependent ADCC mediated by CD16+ effector cells.
We first investigated the number of circulating CD16+ mononuclear cells in relation to FCGR3A-158V/F polymorphism in 54 blood donors. We then compared the affinity of the two allotypic forms of FcRIIIa for rituximab. Finally, we studied the influence of FCGR3A-158V/F polymorphism on the relationship between rituximab concentration and rituximab-dependent NK cell-mediated cytotoxicity.
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MATERIALS AND METHODS |
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TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Cell Culture.
Daudi cells were cultured in 75-cm2 tissue culture flasks (Falcon 3024; Becton Dickinson Labware Europe, Le Pont De Claix, France) at 37°C in 5% CO2 humidified air. Cells were grown in culture medium: RPMI 1640 (Eurobio, Les Ulis, France) supplemented with 10% heat-inactivated FCS (Invitrogen SARL, Cergy Pontoise, France); 2 mM L-glutamine (Bio Whittaker Europe, Verviers, Belgium); 1 mM sodium pyruvate (Invitrogen); 50 units/ml penicillin; and 50 µg/ml streptomycin (Bio Whittaker Europe).
Isolation of Peripheral Blood Mononuclear Cells (PBMCs) and Preparation of Peripheral Blood Lymphocytes, Monocytes, T Cells, and NK Cells.
PBMCs and peripheral blood lymphocytes were prepared from the peripheral venous blood of blood donors by Lymphoprep (AbCys S.A., Paris, France) centrifugation as described previously (26)
. Monocytes and T cells were positively selected using MACS CD14 and MACS CD3 MicroBeads (Miltenyi Biotec, Paris, France), respectively, and NK cells were negatively selected using MACS NK Cell Isolation Kit (Miltenyi Biotec) according to the manufacturer’s recommendations. The labeled cells were retained on a MACS column in the magnetic field of a VarioMACS separator (Miltenyi Biotec).
Preparation of Target Cells.
Daudi cells were washed and resuspended in RPMI 1640. Cells (10 x 106) were labeled for 90 min with 100 µCi of Na251CrO4 (DuPont-NEN, Les Ulis, France) at 37°C in 5% CO2, washed three times in RPMI 1640, and incubated for 1 h with culture medium to allow spontaneous release. Finally, 51Cr-labeled cells were washed twice and resuspended in culture medium, and 2 x 104 cells/well were added to 96-well round-bottomed plates.
Cytotoxicity Assay.
Cytotoxicity assay was performed as described previously (26)
. Rituximab or 3G8 mAb at the indicated final concentration was added to the 51Cr-labeled target cells immediately before adding effector cells. Each assay was set up in triplicate, and the results were expressed as the percentage of specific lysis: (experimental cpm – spontaneous cpm) x 100/(maximum cpm – spontaneous cpm).
Analysis of the Relationship between Rituximab Concentration and Daudi Cell Lysis.
The concentration-effect relationship of rituximab-dependent cytotoxicity by NK cells was analyzed for each individual with an Emax model, using WinNonLin 3.1 (Pharsight, Mountain View, CA), as follows:
E = E0 + (Emax x C)/(EC50 + C) where E is the effect (lysis), E0 is basal lysis in the absence of rituximab (effector cells alone), Emax is maximum lysis induced by rituximab, C is rituximab concentration, and EC50 is the concentration of rituximab leading to 50% of Emax. Pharmacodynamic parameters were compared with a nonparametric Mann-Whitney test, using Statistica 5.5 A (StatSoft, Maisons-Alfort, France). Results were considered significant if P < 0.05. E/Emax percentage at a given rituximab concentration was calculated as follows: % = 100 x predicted lysis at given rituximab concentration/Emax.
Enumeration of Circulating CD16+ PBMCs.
Phenotypic analysis of CD16+ PBMCs was performed according to a standard no-wash whole-blood procedure using a PrepPlus workstation (Beckman Coulter). Blood samples (100 µl) were incubated with 20 µl of FITC-conjugated anti-CD16, 5 µl of phycoerythrin-conjugated anti-CD56, and 20 µl of phycoerythrin-cyanin 5.1-conjugated anti-CD3 mAbs for 15 min at 18–20°C. RBC lysis and cell fixation were performed using a TQ-Prep workstation and ImmunoPrep reagent system (Beckman Coulter) following the manufacturer’s recommendations. Cells were analyzed using an EPICS-XL-MCL flow cytometer (Beckman Coulter) as described previously (27)
.
Binding of Rituximab to Daudi Cells.
Daudi cells (5 x 105) in PBS were incubated with varying concentrations of rituximab for 30 min at 4°C. After two washes with PBS, cells were incubated (30 min at 4°C) with FITC-conjugated goat antihuman IgG F(ab')2. After two washes with PBS, cells were analyzed by flow cytometry. The percentage of CD20 occupancy on Daudi cells at a given rituximab concentration was calculated as follows: % = 100 x (MFI at given rituximab concentration – MFI in absence of rituximab)/(MFI at 0.2 µg/ml rituximab – MFI in absence of rituximab), where MFI is mean fluorescence intensity.
Rituximab-Binding Properties of FcRIIIa.
NK cells (15 x 104) were incubated with varying concentrations of rituximab (30 min, 4°C). Cells were then incubated with FITC-conjugated 3G8 (0.1 µg/ml) and phycoerythrin-conjugated anti-CD56 mAb (30 min, 4°C), washed twice in PBS at 4°C, and analyzed by flow cytometry. Results were expressed as the percentage of inhibition of 3G8 mAb binding: (MFI in absence of rituximab – MFI in presence of rituximab) x 100/(MFI in absence of rituximab). HPLC analysis of rituximab preparation was performed periodically to ensure maintenance of the monomeric IgG. In addition, the lack of binding of rituximab preparation to polymorphonuclear cells was verified periodically by flow cytometry (5)
.
FCGR3A-158V/F Genotyping.
Genotyping of the FCGR3A-158V/F polymorphism was performed using a single-step multiplex allele-specific PCR and fluorescence melting curve analysis assay as described previously (28)
.
Statistical Analysis.
Differences between the three genotypes were compared by Kruskal-Wallis nonparametric ANOVA test followed by Mann-Whitney tests. Within-genotype differences in 3G8 binding were compared by Wilcoxon paired nonparametric test. Statistica 5.5 A (StatSoft) was used, and results were considered significant if P < 0.05.
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RESULTS |
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TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. The three groups were not different in terms of sex or age. When all samples were analyzed together, we found that 13.8% of PBMCs, 9.4% of monocytes, and 14.7% of lymphocytes were CD16+. The vast majority of CD16+ PBMCs were NK cells (77.1%), whereas CD16+ monocytes and CD3+CD16+ lymphocytes represented 11.9% and 9.7% of these cells, respectively. No difference was found among the three genotype groups in terms of number of circulating CD16+ mononuclear cells, CD16+ monocytes, CD3+CD16+ T cells, and CD3-CD16+ NK cells (Table 1)
. The level of CD16 expression on monocytes was slightly higher than that observed on NK cells whatever the genotype, whereas it was very low on CD3+CD16+ T cells. Finally, higher binding of anti-CD16 3G8 mAb to NK cells and monocytes was observed in FCGR3A-158V homozygous and heterozygous donors compared with homozygous FCGR3A-158F donors (Table 1)
. Given that the binding of several other anti-CD16 mAbs is similar on NK cells from VV and FF donors (2)
, it is likely that the difference in binding of 3G8 reflects a greater affinity of this mAb for the V allotype.
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RIIIa.RIIIa affinity for IgG1 (2)
. To address this question, we compared the ability of rituximab (IgG1) to inhibit the binding of FITC-conjugated 3G8 mAb (29)
with NK cells from VV and FF donors. A 50% inhibition of 3G8 mAb binding to VV and FF NK cells was achieved with less than 0.15 mg/ml and more than 0.8 mg/ml rituximab, respectively (Fig. 1)
. The difference in the ability of rituximab to block 3G8 mAb binding to FcRIIIa on VV and FF NK cells cannot result from a difference in the affinity of 3G8 mAb binding to FcRIIIa allotypes. Indeed, the higher binding of 3G8 mAb to VV NK cells (Table 1)
should lead to less rather than more blockade of 3G8 mAb binding in the presence of rituximab. These findings thus indicate that FcRIIIa expressed on NK cells from VV donors binds rituximab with higher affinity than FcRIIIa expressed on NK cells from FF donors.
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. Weak binding of rituximab was detected with 0.0006 µg/ml rituximab. Binding then increased dramatically with increasing concentrations reaching a maximum at 0.2 µg/ml.
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RIIIa Stimulation.RIIIa engagement. Daudi cells express CD32/FcRII, which binds mouse IgG1 (30)
. They may therefore be used as targets in a redirected killing assay in the presence of anti-CD16 3G8 mAb. Daudi cells were resistant to lysis in the presence of anti-CD56 T199 mAb (data not shown), whereas they were killed very efficiently in the presence of 3G8 mAb (Fig. 3)
. Although 3G8 mAb bound slightly more efficiently to NK cells from VV donors (Table 1)
, the lysis observed with VV and FF NK cells in the presence of 3G8 mAb was similar and was also equivalent to that observed in the presence of saturating amounts of rituximab (Fig. 3)
.
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. The relationship between Daudi cell lysis and rituximab concentrations was analyzed for each individual using an Emax model. Basal lysis and maximal lysis induced by rituximab with NK cells from VV and FF donors were not different: E0 values obtained with VV and FF NK cells were 11.3 ± 9.9% and 8.3 ± 3.5% specific lysis, respectively, P = 1; whereas Emax values were 47.4 ± 6.2% and 41.9 ± 9.5% specific lysis, respectively, P = 0.3939. By contrast, the rituximab concentration resulting in 50% lysis of target cells obtained with NK cells from VV donors was on average 4.2 times lower than that obtained with NK cells from FF donors: EC50s obtained with VV and FF NK cells were 0.00096 ± 0.00058 and 0.00402 ± 0.00236 µg/ml, respectively, P = 0.0043.
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DISCUSSION |
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TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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A human CD20-expressing target cell was required to study the influence of FCGR3A-158 polymorphism on the rituximab-dependent CD16+ effector cell-mediated cytotoxicity in vitro. The Burkitt lymphoma cell line Daudi was chosen for several reasons, although Daudi cells are not representative of NHL cells. First, Daudi cells are resistant to lysis by effector cells in the absence of antibodies, and rituximab binds efficiently to them (Fig. 2)
. Second, they express CD32/FcRII and therefore can be used as target cells in a redirected killing assay. Finally, the fact that they are HLA-class I negative (31)
allows comparison of the cytolytic activities of effector cells from different donors, independently of the HLA-specific inhibitory receptors expressed on these effectors. In agreement with a recent study (32)
, we found that Daudi cells were not killed by purified monocytes or T cells in the presence of a saturating concentration of rituximab (not shown), whereas they were killed very efficiently by NK cells. These results suggest that NK cells are important effector cells in the mechanism of action of rituximab, although they do not rule out the possibility that other CD16+ effector cells, especially activated macrophages, could mediate rituximab-dependent cytotoxicity in vivo. Analysis of the concentration-effect relationship of rituximab-dependent NK cell-mediated cytotoxicity showed that the EC50 obtained with NK cells from VV donors was 4.2 times lower than that obtained with NK cells from FF donors, whereas Emax and E0 were not different. These results are in accordance with the previous observation that human low-IgG-binding NK cells were able to lyse chicken erythrocytes better than NK cells from high-IgG-binding NK cells in the presence of low concentrations of rabbit antichicken erythrocyte IgG (5)
. Shields et al. (33)
have shown that some substitutions in the Fc sequence improved both the binding of monomeric human anti-IgE to FcRIIIA-transfected Chinese hamster ovary cells and Herceptin-mediated ADCC of SKBR-3 cells by NK cells. These effects were more pronounced on the FcRIIIA-158F than on the FcRIIIA-158V allotype. In addition, it was shown that the more the substitutions improved binding to FcRIIIA, the more they increased ADCC, whatever the genotype. Finally, the differences in ADCC were observed in the presence of a concentration of Herceptin variant (2 ng/ml) that is very close to the EC50 observed in our study. Thus, our results are consistent with these findings. Interestingly, it can be calculated from the results shown in Fig. 2
and Fig. 4
that less than 5% and 15% of CD20 molecules on Daudi cells are bound by rituximab at the EC50s obtained with VV and FF NK cells, respectively. In addition, rituximab concentrations yielding more than 40% occupancy of CD20 (i.e., above 0.02 µg/ml) were sufficient to obtain more than 80% of maximum lysis, whatever the genotype. Thus, the increased ADCC associated with expression of the FcRIIIa-158V allotype on NK cells was restricted to a rituximab concentration range weakly sensitizing CD20 on Daudi cells. We therefore conclude that both the level of opsonization and the 158V/F FcRIIIa polymorphism influence the killing of Daudi cells.
The fact that VV and FF NK cells killed Daudi cells similarly after optimal FcRIIIa engagement by saturating concentrations of rituximab or by 3G8 anti-CD16 mAb and respond by an indistinguishable rise in Ca2+ to 3G8 (2)
shows that the two FcRIIIa allotypes are not different in terms of intracellular signaling and cytolytic potential. Thus, the functional difference between the two allotypes that we demonstrated at low concentrations results primarily from their difference in IgG1 binding. Flow cytometry studies have shown that human IgG1 binds more strongly to VV NK cells than to FF NK cells (1
, 2
, 5)
. Based on titration of IgG binding to NK cells from low- and high-IgG-binding individuals, Vance et al. (5)
concluded that the absolute number of FcRIIIa receptors rather than FcRIIIa affinity accounts for the difference in IgG binding. Conversely, the fact that similar fluorescence intensities were observed with several anti-CD16 mAbs on NK cells from VV and FF donors led Wu et al. (2)
to propose that these cells express similar levels of FcRIIIa and that 158-V/F polymorphism affects FcRIIIa affinity. However, we observed a significantly higher binding of 3G8 anti-CD16 mAb on NK cells and monocytes from VV and VF donors compared with FF donors in accordance with previous reports (1
, 5)
. Conversely, the binding of the DJ130 anti-CD16 mAb is higher on NK cells from FF and VF donors than on those from VV donors.6
These conflicting results show the important limitations in the use of anti-CD16 mAbs and flow cytometry to conclude on the levels of FcRIIIa expression. However, our results (Fig. 1)
unambiguously demonstrate that FcRIIIa-158V has a higher affinity for rituximab—and probably for all human IgG1 including therapeutic recombinant mAbs—than FcRIIIa-158F.
The rituximab-depleting effect observed in vivo is the result of different complementary mechanisms including complement-dependent cytotoxicity (6
, 13, 14, 15, 16)
, apoptosis (17, 18, 19)
, phagocytosis, and ADCC (6
, 13)
. The implication of both FcR and C1q in the in vivo antitumor effect of rituximab against CD20+ lymphoma cell lines has been clearly demonstrated in murine models (20
, 21)
, suggesting that ADCC and complement activation are essential for rituximab therapeutic effect. In addition, the fact that opsonization of target cells with complement components results in increased lysis by NK cells that express the CD11b/CD18 receptor (34
, 35)
strongly suggests that ADCC and complement activation may have a cooperative activity in vivo (32
, 36)
. Complement-dependent cytotoxicity is mainly dependent on lymphoma cell variability, especially on both their CD20 and complement regulatory protein membrane expression (13
, 14
, 16)
, although response to rituximab therapy has been shown to be independent of the level of expression of these proteins on the tumor tissue (37)
. These parameters have no detectable influence on apoptosis, phagocytosis, or ADCC (13)
. By contrast, the present study is the first to show that rituximab-mediated ADCC is dependent on the allotypic form of FcRIIIa expressed by NK cells. Therefore, variability at both the tumor cell level and the patient’s immune system level may influence the response to rituximab, in addition to the tumor burden at the time of treatment (10)
and rituximab concentrations obtained in patients (8
, 38)
.
In agreement with results obtained with Raji and WIL.2-S B-cell lines (39
, 40)
, lysis of Daudi cells was detected with concentration around 0.0001 µg/ml rituximab and reached a maximum at around 0.1 µg/ml, whatever the genotype. The difference in the cytotoxic response between VV and FF NK cells was observed over the 0–0.02 µg/ml range. On the other hand, serum rituximab concentrations observed in vivo range from around 1000 µg/ml for peak concentrations to around 20 µg/ml several weeks after ending the infusions (38
, 41)
, raising the question of the clinical relevance of our in vitro result. However, rituximab concentrations at the site of action (mainly in lymphadenopathies) may be different from those measured in the blood. In addition, for anticancer agents, the duration of drug exposure above a defined threshold concentration is sometimes more important than the extent of the exposure (42
, 43) . Using the data presented by Berinstein et al. (38)
, it can be calculated that responders have a longer half-life than nonresponders (12 versus 8 days) and that the former group has been exposed to concentrations above 0.0001 µg/ml (i.e., the concentration at which ADCC was detected in vitro) during 20 months versus 13 months for nonresponders. It has also been reported that some NHL patients have delayed clinical response (between day 78 and month 12 after rituximab infusion; Ref. 10
). This observation shows that long-lasting effector mechanisms are involved in the therapeutic effect of rituximab and suggests that the difference between VV and FF NK cells observed in our in vitro model may be clinically relevant. Thus, the present study supports the conclusion that the FCGR3A genotype is associated with the therapeutic action of rituximab because it affects the relationship between rituximab concentration and B-cell lysis by NK cells. The consequence of the present findings is that rituximab dose or administration schedule may be adjusted in FF patients to ensure a longer exposure to effective concentrations to obtain a better clinical response. More generally, such a pharmacogenetic approach has to be taken into account to improve therapeutic efficacy of cytolytic mAbs in addition to methods that have been shown to enhance NK cell response to tumor cells, such as engineering the Fc portion to increase mAb binding to FcRIIIa (32
, 44)
or stimulating NK cells by cytokines (35
, 45 , 46)
.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Requests for reprints: Gilles Thibault, Laboratoire d’Immunologie, Centre Hospitalier Régional et Universitaire, 2 boulevard Tonnellé, 37044 Tours Cedex, France. Phone: 33-2-4736-6081; Fax: 33-2-4736-6095; E-mail: thibault{at}med.univ-tours.fr
6 S. Dall’Ozzo, S. Tartas, G. Paintaud, G. Cartron, P. Colombat, P. Bardos, H. Watier, and G. Thibault, unpublished observations. 
Received 9/10/03. Revised 4/ 1/04. Accepted 5/ 4/04.
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 C. Meyer zum Buschenfelde, Y. Feuerstacke, K. S. Gotze, K. Scholze, and C. Peschel GM1 Expression of Non-Hodgkin's Lymphoma Determines Susceptibility to Rituximab Treatment Cancer Res., July 1, 2008; 68(13): 5414 - 5422. [Abstract] [Full Text] [PDF]
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P. V. Beum, M. A. Lindorfer, F. Beurskens, P. T. Stukenberg, H. M. Lokhorst, A. W. Pawluczkowycz, P. W. H. I. Parren, J. G. J. van de Winkel, and R. P. Taylor Complement Activation on B Lymphocytes Opsonized with Rituximab or Ofatumumab Produces Substantial Changes in Membrane Structure Preceding Cell Lysis J. Immunol., July 1, 2008; 181(1): 822 - 832. [Abstract] [Full Text] [PDF]
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 J. Chen, C. Su, Q. Lu, W. Shi, Q. Zhang, X. Wang, J. Long, Q. Yang, L. Li, X. Jia, et al. Generation of adenovirus-mediated anti-CD20 antibody and its effect on B-cell deletion in mice and nonhuman primate cynomolgus monkey Mol. Cancer Ther., June 1, 2008; 7(6): 1562 - 1568. [Abstract] [Full Text] [PDF]
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N. Congy-Jolivet, A. Bolzec, D. Ternant, M. Ohresser, H. Watier, and G. Thibault Fc{gamma}RIIIa Expression Is Not Increased on Natural Killer Cells Expressing the Fc{gamma}RIIIa-158V Allotype Cancer Res., February 15, 2008; 68(4): 976 - 980. [Abstract] [Full Text] [PDF]
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A. Kretz-Rommel, F. Qin, N. Dakappagari, R. Cofiell, S. J. Faas, and K. S. Bowdish Blockade of CD200 in the Presence or Absence of Antibody Effector Function: Implications for Anti-CD200 Therapy J. Immunol., January 15, 2008; 180(2): 699 - 705. [Abstract] [Full Text] [PDF]
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S. Varchetta, N. Gibelli, B. Oliviero, E. Nardini, R. Gennari, G. Gatti, L. S. Silva, L. Villani, E. Tagliabue, S. Menard, et al. Elements Related to Heterogeneity of Antibody-Dependent Cell Cytotoxicity in Patients Under Trastuzumab Therapy for Primary Operable Breast Cancer Overexpressing Her2 Cancer Res., December 15, 2007; 67(24): 11991 - 11999. [Abstract] [Full Text] [PDF]
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E. Hatjiharissi, L. Xu, D. D. Santos, Z. R. Hunter, B. T. Ciccarelli, S. Verselis, M. Modica, Y. Cao, R. J. Manning, X. Leleu, et al. Increased natural killer cell expression of CD16, augmented binding and ADCC activity to rituximab among individuals expressing the Fc{gamma}RIIIa-158 V/V and V/F polymorphism Blood, October 1, 2007; 110(7): 2561 - 2564. [Abstract] [Full Text] [PDF]
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Y. Li, M. E. Williams, J. B. Cousar, A. W. Pawluczkowycz, M. A. Lindorfer, and R. P. Taylor Rituximab-CD20 Complexes Are Shaved from Z138 Mantle Cell Lymphoma Cells in Intravenous and Subcutaneous SCID Mouse Models J. Immunol., September 15, 2007; 179(6): 4263 - 4271. [Abstract] [Full Text] [PDF]
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 Z. Mitrovic, I. Aurer, I. Radman, R. Ajdukovic, J. Sertic, and B. Labar FC{gamma}RIIIA and FC{gamma}RIIA polymorphisms are not associated with response to rituximab and CHOP in patients with diffuse large B-cell lymphoma Haematologica, July 1, 2007; 92(7): 998 - 999. [Abstract] [Full Text] [PDF]
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 D. B. Lowe, M. H. Shearer, C. A. Jumper, R. K. Bright, and R. C. Kennedy Fc{gamma} Receptors Play a Dominant Role in Protective Tumor Immunity against a Virus-Encoded Tumor-Specific Antigen in a Murine Model of Experimental Pulmonary Metastases J. Virol., February 1, 2007; 81(3): 1313 - 1318. [Abstract] [Full Text] [PDF]
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D. H. Kim, H. D. Jung, J. G. Kim, J.-J. Lee, D.-H. Yang, Y. H. Park, Y. R. Do, H. J. Shin, M. K. Kim, M. S. Hyun, et al. FCGR3A gene polymorphisms may correlate with response to frontline R-CHOP therapy for diffuse large B-cell lymphoma Blood, October 15, 2006; 108(8): 2720 - 2725. [Abstract] [Full Text] [PDF]
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J. A. Bowles, S.-Y. Wang, B. K. Link, B. Allan, G. Beuerlein, M.-A. Campbell, D. Marquis, B. Ondek, J. E. Wooldridge, B. J. Smith, et al. Anti-CD20 monoclonal antibody with enhanced affinity for CD16 activates NK cells at lower concentrations and more effectively than rituximab Blood, October 15, 2006; 108(8): 2648 - 2654. [Abstract] [Full Text] [PDF]
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T. van Meerten, R. S. van Rijn, S. Hol, A. Hagenbeek, and S. B. Ebeling Complement-Induced Cell Death by Rituximab Depends on CD20 Expression Level and Acts Complementary to Antibody-Dependent Cellular Cytotoxicity. Clin. Cancer Res., July 1, 2006; 12(13): 4027 - 4035. [Abstract] [Full Text] [PDF]
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B. Clemenceau, N. Congy-Jolivet, G. Gallot, R. Vivien, J. Gaschet, G. Thibault, and H. Vie Antibody-dependent cellular cytotoxicity (ADCC) is mediated by genetically modified antigen-specific human T lymphocytes Blood, June 15, 2006; 107(12): 4669 - 4677. [Abstract] [Full Text] [PDF]
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S. Iida, H. Misaka, M. Inoue, M. Shibata, R. Nakano, N. Yamane-Ohnuki, M. Wakitani, K. Yano, K. Shitara, and M. Satoh Nonfucosylated Therapeutic IgG1 Antibody Can Evade the Inhibitory Effect of Serum Immunoglobulin G on Antibody-Dependent Cellular Cytotoxicity through its High Binding to Fc{gamma}RIIIa. Clin. Cancer Res., May 1, 2006; 12(9): 2879 - 2887. [Abstract] [Full Text] [PDF]
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R. Godal, U. Keilholz, L. Uharek, A. Letsch, A. M. Asemissen, A. Busse, I.-K. Na, E. Thiel, and C. Scheibenbogen Lymphomas are sensitive to perforin-dependent cytotoxic pathways despite expression of PI-9 and overexpression of bcl-2 Blood, April 15, 2006; 107(8): 3205 - 3211. [Abstract] [Full Text] [PDF]
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 G. A. Lazar, W. Dang, S. Karki, O. Vafa, J. S. Peng, L. Hyun, C. Chan, H. S. Chung, A. Eivazi, S. C. Yoder, et al. Engineered antibody Fc variants with enhanced effector function. PNAS, March 14, 2006; 103(11): 4005 - 4010. [Abstract] [Full Text] [PDF]
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P. R. Hinton, J. M. Xiong, M. G. Johlfs, M. T. Tang, S. Keller, and N. Tsurushita An Engineered Human IgG1 Antibody with Longer Serum Half-Life J. Immunol., January 1, 2006; 176(1): 346 - 356. [Abstract] [Full Text] [PDF]
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D. Ternant, M. Ohresser, C. Thomas, G. Cartron, H. Watier, G. Paintaud, A. Hubsch, M. Spycher, J. Bichler, and S. Miescher Dose-response relationship and pharmacogenetics of anti-RhD monoclonal antibodies Blood, August 15, 2005; 106(4): 1503 - 1505. [Full Text] [PDF]
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 M. D. Pegram Molecular Determinants of Trastuzumab Response/Resistance Am. Assoc. Cancer Res. Educ. Book, April 1, 2005; 2005(1): 155 - 159. [Full Text] [PDF]
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) or 0.2 µg/ml 3G8 mAb (
). Cytotoxicity against Daudi cells is expressed as the mean ± SD percentage of specific lysis (n = 6 VV and 6 FF)
, VV;