Species Specificity of Anti-β2 Glycoprotein I Autoantibodies and Its Relevance to Anticardiolipin Antibody Quantitation

Some patients suspected of having antiphospholipid antibody syndrome (APS) were found to be positive for anti-β2 glycoprotein I (β2GPI) antibodies despite negative results for antibodies to cardiolipin (ACA). Since the major source of β2GPI in the ACA assay is animal (usually bovine) serum, we studied the influence on ACA quantitation of the species specificity of anti-β2GPI antibodies from patients with various autoimmune disorders, mostly systemic lupus erythematosus and primary APS. Ninety-seven sera were selected based on IgG (n = 76) or IgM (n = 64) positivity by ELISA using γ-irradiated plates coated with human or bovine purified β2GPI. A higher proportion of IgM (43.7%) than IgG (7.9%) reacted to human, but not bovine, β2GPI. Furthermore, from the samples reactive to both proteins, the ratio of antibody level against bovine to that against human β2GPI was 1.08 ± 0.58 for IgG and 0.58 ± 0.3 for IgM (p <10−5). IgG and IgM ACA were detected in 78 and 40 sera, respectively; concordance between the two ELISAs for ACA and anti-β2GPI antibodies was 94% for IgG and 75% for IgM. Out of 28 IgM showing recognition restricted to human β2GPI, 21 were missed by the ACA assay, possibly because of lower concentrations of β2GPI in those patients’ sera. The antibody reactivity pattern towards human and bovine β2GPI of individual sera showed no variation with time and was related to the relative antibody avidity for each protein. A murine anti-human β2GPI monoclonal antibody, 9G1, that cross-reacts with bovine β2GPI, competed to a large extent with the patients’ anti-β2GPI antibody binding sites whatever isotype involved or protein recognized. Therefore, anti-β2GPI antibodies of IgM isotype display a marked preference for human compared to bovine β2GPI responsible for frequent inconsistencies in the ACA assay.

Development of an ELISA for Autoantibodies to Prothrombin Showing their Prevalence in Patients with Lupus Anticoagulants

Some lupus anticoagulants (LA) have been shown to be directed against phospholipid-bound prothrombin. While developing an ELISA to detect anti-prothrombin autoantibodies in patient serum or plasma, no or very low signal was observed using human prothrombin immobilized on plain polystyrene plates. In contrast, the same LA-positive samples bound specifically to prothrombin coated on γ-irradiated plates, depending on the radiation dose, in the absence of added calcium and phospholipid. Optimization of the assay required the addition of 0.1% Tween 20 to the buffers. Antibody specificity for immobilized prothrombin was ascertained by competition using liposome-bound prothrombin, since fluid-phase prothrombin competed poorly. Seventy-seven of 139 patients (55.4%) with LA related to a variety of underlying diseases possessed anti-prothrombin antibodies (27 IgG, 35 IgM and 15 both isotypes), either isolated or more often associated with anti-(β2 glycoprotein I (β2GPI) antibodies. These included 67-71% of the patients with systemic lupus erythematosus and related disorders, primary antiphospholipid antibody syndrome or drug-induced LA (autoimmune groups), but only 19-20% of those with infection or malignancy (p <0.001). As previously shown for anti-β2GPI antibodies, IgG2 was the predominant IgG subclass reactive with prothrombin. Thus, autoimmune patients with LA have a high incidence of antibodies to β2GPI and prothrombin, the binding of which could similarly require high antigen density and/or exposure of cryptic epitopes resulting from protein interaction with an irradiated (i. e. more anionic) polystyrene surface.

Immunomonitoring of graft-versus-host minor histocompatibility antigen correlates with graft-versus-host disease and absence of relapse after graft

BACKGROUND

After HLA-identical hematopoietic stem cell transplantation, minor histocompatibility (mH) antigen alloreactivity plays a dominant role in the development of graft-versus-host disease (GVHD) and graft versus leukemia (GVL).

STUDY DESIGN AND METHODS

We have analyzed the mH alloreactivity (enzyme-linked immunospot [ELISpot] for interferon-gamma[IFN-gamma] assay) from 24 donor/recipient pairs over a period of 2 years of follow-up and correlated such alloreactivity with the development of GVHD or absence of relapse. Circulating specific T cells anti-mH with multimer HLA-peptides were also studied.

RESULTS

We show by ELISpot IFN-gamma assay that alloreactivity during the first 3 months from donor versus recipient or donor versus mismatched identified mH antigens is associated with acute GVHD and GVL effect. In addition, we demonstrate that the donor-versus-recipient reactivity observed after the third month is highly associated with chronic GVHD and GVL (p = 0.0007). Finally, we show by multimer HLA-peptide assay that mH epitope-specific T cells present after 3 months are statistically related to the GVL effect.

CONCLUSIONS

Our results provide a robust method to monitor mH antigen graft-versus-host reaction and suggest that current identified mH have predictive value on GVHD and GVL.

Development of autologous cytotoxic CD4+T clones in a human model of B-cell non-Hodgkin follicular lymphoma

Immunotherapy for cancer aims to generate cytotoxic cells that are capable of eradicating tumour cells. It has been well demonstrated that helper, non-cytotoxic CD4(+) T cells are important for the induction and maintenance of anti-tumour immunity exerted by cytotoxic CD8(+) T cells. In contrast, the existence of direct anti-tumour, effector cytotoxic CD4(+) T cells remains elusive, mainly due to the paucity of reliable experimental data, especially in human B-cell non-Hodgkin lymphomas. This study developed an appropriate, autologous follicular B-cell non-Hodgkin follicular lymphoma model, including the in vitro establishment of a malignant, human leucocyte antigen class I (HLA-I) deficient B-cell line, and the generation of three autologous anti-tumour cytotoxic CD4(+) T-cell clones originating from the peripheral blood of the same patient. These three clones were considered as tumour specific, because they were capable of killing the malignant, HLA-I-deficient B-cell line through a classical HLA-II restricted perforin-mediated pathway, but did not lyse the Epstein-Barr virus-infected autologous normal B lymphocytes. All three CD4(+)clones were T-cell receptor Vbeta17-Dbeta1-Jbeta1.2 and exhibited an identical complementarity-determining region 3, suggesting the immunodominance of a single peptide antigen presented by tumour cells. Such lymphoma models would provide a useful tool for in vivo expansion and the adoptive transfer of selected CD4(+) cytotoxic cells in immunotherapeutic strategies.

Anti-Gal-mediated targeting of human B lymphoma cells to antigen-presenting cells: a potential method for immunotherapy using autologous tumor cells

BACKGROUND AND OBJECTIVES

The residual tumor cells remaining after completion of standard chemotherapy and radiation treatment in B lymphoma patients, may be eradicated by active immunotherapy that stimulates tumor-specific T lymphocytes. Irradiated autologous lymphoma cells expressing tumor-associated antigens (TAA) may serve as a potential tumor vaccine, provided that they are effectively targeted to the antigen-presenting cells (APC). We propose exploiting the natural anti-Gal antibody in order to target vaccinating tumor cells to APC. Anti-Gal constitutes 1% of IgG in human serum and interacts specifically with the alpha-gal epitope (Galalpha1-3Galphalbeta1-4GlcNAc-R).

DESIGN AND METHODS

Alpha-gal epitopes were synthesized in vitro on the membrane of primary lymphoma cells by using the recombinant glycosylation enzyme alpha1,3galactosyltransferase (alpha1,3GT). Processed tumor cells were opsonized by purified anti-Gal antibodies and studied for uptake (phagocytosis) by APC including monocyte-derived macrophages and dendritic cells. Cross-presentation of tumor antigens after phagocytosis of processed MHC-I negative lymphoma cells was measured by activation of a tumor-specific CD8+ T-cell line.

RESULTS

We demonstrate synthesis of alpha-gal epitopes on freshly isolated B lymphoma cells of various types following the use of the recombinant enzyme alpha1,3GT. The subsequent binding of anti-Gal to the de novo synthesized alphagal epitopes opsonizes these tumor cells for effective uptake by macrophages and dendritic cells, through phagocytosis mediated by FcgammaR1 (CD64). Moreover, anti-Gal-mediated phagocytosis resulted in cross-presentation of TAA by dendritic cells.

INTERPRETATION AND CONCLUSIONS

This study suggests that immunization with irradiated autologous lymphoma cells processed to express alpha-gal epitopes will result in anti-Gal-mediated, in vivo targeting of the autologous tumor vaccine to APC.

Quantitating Effector and Regulatory T Lymphocytes in Immune Responses by Limiting Dilution Analysis Modeling

Although there is currently no doubt that regulatory lymphocytes represent a master player in the immune system, a major unresolved problem is the accurate quantitation of these cells among unfractionated cell populations. This difficulty mainly arises because there are no specific immunophenotypic markers that can reliably discriminate between effector and regulatory lymphocytes. To face this problem, we have developed computational models of limiting dilution analyses addressing the question of the accurate estimation of the frequencies of effector and regulatory cells functionally engaged in an immune response. A set of generic equations were provided to form a framework for modeling limiting dilution data, enabling discrimination between qualitatively different models of suppression. These models include either one or two subpopulations of regulatory cells, featured by either low or potent regulatory activity. The potential of this modeling approach was illustrated by the accurate determination of the frequencies of effector and regulatory T lymphocytes in one real limiting dilution experiment of CD4+ CD25+ T lymphocytes performed in the context of an allogeneic response in the human system. The crucial advantage of the limiting dilution method over the "static, phenotype-based" method is the dynamic evaluation of effector and regulatory T cell biology through their actual functional activity.

Expression of the myeloid-associated marker CD33 is not an exclusive factor for leukemic plasmacytoid dendritic cells

A new entity of acute leukemia coexpressing CD4(+)CD56(+) markers without any other lineage-specific markers has been identified recently as arising from lymphoid-related plasmacytoid dendritic cells (pDCs). In our laboratory, cells from a patient with such CD4(+)CD56(+) lineage-negative leukemia were unexpectedly found to also express the myeloid marker CD33. To confirm the diagnosis of pDC leukemia despite the CD33 expression, we demonstrated that the leukemic cells indeed exhibited pDC phenotypic and functional properties. In 7 of 8 other patients with CD4(+)CD56(+) pDC malignancies, we were able to confirm that the tumor cells expressed CD33 although with variable expression levels. CD33 expression was shown by flow cytometry, reverse transcriptase-polymerase chain reaction, and immunoblot analysis. Furthermore, CD33 monoclonal antibody stimulation of purified CD4(+)CD56(+) leukemic cells led to cytokine secretion, thus confirming the presence of a functional CD33 on these leukemic cells. Moreover, we found that circulating pDCs in healthy individuals also weakly express CD33. Overall, our results demonstrate that the expression of CD33 on CD4(+)CD56(+) lineage-negative cells should not exclude the diagnosis of pDC leukemia and underline that pDC-specific markers should be used at diagnosis for CD4(+)CD56(+) malignancies.

Impairment of death-inducing signalling complex formation in CD95-resistant human primary lymphoma B cells

Multiple mechanisms exist by which tumour cells can escape CD95-mediated apoptosis. Previous studies by our laboratory have shown that primary B cells from non-Hodgkin's Lymphoma (B-NHL) were resistant to CD95-induced cell death. In the current study, we have analysed the mechanisms underlying CD95 resistance in primary human lymphoma B cells. We report that FADD (FAS-associated death domain protein) and caspase-8 were constitutively expressed in lymphoma B cells and that the CD95 pathway was blocked upstream to caspase-8 activation. However, caspase-8 was processed and functional after treatment with staurosporine (STS). We found that the expression levels of FLICE (FADD-like interleukin-1 beta-converting enzyme)-Inhibitory Protein (c-FLIP) and Bcl-2-related proteins were heterogeneous in B-NHL cells and were not related to CD95 resistance. Finally, we report the absence of a CD95-induced signalling complex [death-inducing signalling complex (DISC)] in lymphoma B cells, with no FADD and caspase-8 recruitment to CD95 receptor. In contrast, DISC formation was observed in CD95-resistant non-tumoural (NT) B cells. Therefore, we propose that the absence of DISC formation in primary lymphoma B cells may contribute to protect these cells from CD95-induced apoptosis.

Leukemic plasmacytoid dendritic cells share phenotypic and functional features with their normal counterparts

This work aims to further characterize the newly described leukemic plasmacytoid dendritic cells (LPDC), for which we had previously demonstrated their normal, PDC-like ability to produce IFN-alpha. In addition, LPDC also express the specific antigens BDCA-2 and BDCA-4. Importantly, they become fully competent antigen-presenting cells (APC) after a short maturation induced by IL-3 + CD40L or virus, exhibiting a characteristic APC phenotype (high expression of CD83 and of the costimulatory molecules CD40, CD80, CD86). Whereas IL-3 + CD40L-activated LPDC prime naive CD4(+) T cells towards a Th2 pathway (IL-4-secreting T cells), virus-activated LPDC drive a Th1 profile (IFN-gamma-secreting T cells). Moreover, we show in one case that LPDC are able to capture, process and present exogenous antigens, leading to the activation of both CD4(+) and CD8(+) T cell clones in an antigen-specific manner. This study further characterizes the phenotype and immunological functions of LPDC.

Quality control for the validation of extracorporeal photopheresis process using the Vilbert-Lourmat UV-A irradiation's system

In agreement with good practices for therapeutic use of human cells, quality control has to be performed to valid the process of extracorporeal photopheresis (ECP) with the Vilbert-Lourmat system. Since no protocol exists, we evaluated a technique based on the measurement of the inhibition of mitogen (PHA, Con-A, OKT3)-induced proliferation, in 164 procedures from 16 patients. Whatever the pathology, we observed a high proliferation rate in most samples, and we obtained over 90% ECP-induced inhibition in as many as 94% of the cases. Since this approach proved to be relevant regarding our objective, a protocol for the ECP process validation is proposed.

In vitro mechanisms of action of rituximab on primary non-Hodgkin lymphomas

To assess the sensitivity of primary non-Hodgkin lymphoma cells to rituximab-mediated cytotoxicity, we compared the potency of several rituximab-mediated killing mechanisms on fresh lymphoma cells. All lymphoma cells tested were equally sensitive to antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-mediated phagocytosis of tumor cells, and rituximab-induced apoptosis. However, they were differentially lysed by complement-dependent cytotoxicity (CDC). We found that taking into account both CD20 and complement regulatory protein expression on tumor cells could predict CDC sensitivity in vitro. Importantly, the sensitivity of lymphoma cells to CDC was consistent with the reported different clinical response rates of lymphomas: rituximab induced high CDC killing of follicular lymphoma cells, whereas mantle cell lymphoma and diffuse large cell lymphoma cells were moderately sensible to CDC, and small lymphocytic lymphoma cells were almost all resistant. We propose that CDC is a determinant mechanism of rituximab-induced killing in vivo. Poor sensitivity to CDC in vitro might predict a poor clinical response, whereas high sensitivity to CDC would only indicate a likelihood of response to rituximab treatment.

Differentiation of anti-tumour cytotoxic T lymphocytes from autologous peripheral blood lymphocytes in non-Hodgkin's lymphomas

We have previously reported that specific anti-tumour cytotoxic T cells (CTL) can be differentiated from tumour-infiltrating lymphocytes (TIL) in non-Hodgkin's lymphoma. We found that the combination of interleukin (IL)-1, IL-2 and IL-12 was very efficient for expansion of CD8+ T-cell receptor (TCR)alphabeta+ T cells and for development of their ability to specifically lyse tumour cells. In this study, we investigated whether anti-tumour T cells could be generated from the peripheral blood of patients using the culture protocol developed for TIL. Autologous T cells and tumour B cells from five patients were included in this study. It was found that polyclonal anti-tumour cytotoxic effector cells were generated when cultured in the presence of IL-1beta, IL-2 and IL-12. Interestingly, tumour cells were lysed by perforin/granzyme-mediated cytolysis and not by CD95-mediated apoptosis. By performing inhibition experiments, it was observed that both CD8+ and CD4+ T cells were responsible for the cytotoxic effect and that they were able to recognize malignant B cells by either a major histocompatibility complex (MHC)-restricted or MHC-non-restricted mechanism. Intriguingly, in addition to interferon-gamma and tumour necrosis factor-alpha, IL-10 was secreted continuously during culture. The source of patient T cells used for the generation of anti-tumour CTL should be based on the results obtained with peripheral blood lymphocytes and TIL.

Identification of a leukemic counterpart of the plasmacytoid dendritic cells

This work aims to demonstrate that CD4(+)CD56(+) malignancies arise from transformed cells of the lymphoid-related plasmacytoid dendritic cell (pDC) subset. The analysis of malignant cells from 7 patients shows that in all cases, like pDCs, leukemic cells are negative for lineage markers CD3, CD19, CD13, CD33, and CD11c but express high levels of interleukin-3 receptor alpha chain (IL-3Ralpha), HLA-DR, and CD45RA. Tumor cells produce interferon-alpha in response to influenza virus, while upon maturation with IL-3 they become a powerful inducer of naive CD4(+) T-cell proliferation and promote their T-helper 2 polarization. As pDCs, leukemic cells also express pre-Talpha and lambda-like 14.1 transcripts, arguing in favor of a lymphoid origin. In addition, malignant cells express significant levels of CD56 and granzyme B. Overall, those observations suggest that CD4(+)CD56(+) leukemic cells could represent the malignant counterpart of pDCs, both of which are closely related to B, T, and NK cells.

Differentiation of antigen-presenting cells (dendritic cells and macrophages) for therapeutic application in patients with lymphoma

The recent clinical trial in lymphoma using tumor antigen-loaded DCs (Hsu et al, Nature Med 1996; 2: 52) demonstrates the efficiency of the use of professional antigen presenting cells (APCs) for taking up, processing and presenting tumor protein in a vaccine strategy in cancer. However, the production of large quantities of clinical grade APCs remains to be resolved. Here, we describe that both dendritic cells (DCs) and macrophages (MOs) can be efficiently differentiated in large numbers from lymphoma patients in spite of their disease and previous therapy. These cells were produced using the VAC and MAK cell processors according to standard operating procedures. DCs and MOs were differentiated from circulating monocytes in gas permeable hydrophobic bags, with 2% autologous serum and in the presence of GM-CSF and IL-13 or GM-CSF alone, respectively. DCs and MOs were then purified by counter flow centrifugation. Phenotypic, morphological and functional analysis showed that cells differentiated from patients with lymphoma present quite similar features to DCs and MOs produced from monocytes of healthy donors. Moreover, we show that MOs, when combined with CD20 antibody (Rituximab), can efficiently engulf tumor cells and propose that a such combination could be used for initiating a clinical trial in lymphoma. Thus, the possibility of producing functional DC and MOs in large amounts in conditions compatible with therapeutic application will allow the development of new immune strategies to eradicate lymphoma.

From the study of tumor cell immunogenicity to the generation of antitumor cytotoxic cells in non-Hodgkin's lymphomas

The question of the immunogenicity of non-Hodgkin's lymphoma (NHL) B cells has been investigated in an attempt to support the development of new immunotherapeutic treatments for this disorder, which remains resistant to conventional treatments in most cases. In the present review, we report and discuss our new findings in the field of NHL B cell immunogenicity. One aspect of our work is the description of the expression and functions of membrane molecules associated with antigen presentation. The expression levels of adhesion molecules was measured, and the relevance of this expression to the sensitivity of malignant B cells to cell-mediated lysis was studied. Since the T cell response relies on the expression of both HLA class I and II molecules, we also investigated whether or not these molecules were present at the surface of NHL B cells. Subsequently, we asked whether antitumor CTL and LAK cells could be developed and analyzed the mechanisms of cell lysis involved. Since the generation of a T cell response requires the expression of the costimulatory molecules CD80 and CD86, we investigated their in vivo expression and their modulation in vitro during contact with responding T lymphocytes. The understanding of the immunogenicity of NHL B cells has enabled us to develop a new culture protocol to induce antitumor specific autologous CTL. The originality of NHL B cells--unlike most other tumor cells--is to be able to function as antigen presenting cells (APC) and to activate a T cell response in the absence of other professional APC. Over the next few years, these findings should allow the generation of anti-NHL specific T cells for adoptive immunotherapy and for the identification of NHL-associated antigens.

Quantification of cellular adhesion molecules on malignant B cells from non-Hodgkin's lymphoma

The expression of five cellular adhesion molecules (CAMs), CD54, CD58, CD11a, CD29 and CD49d, was studied in 113 B cell non-Hodgkin's lymphomas (NHL) and in normal B cells from 12 control lymph nodes. Rather than reporting the percentage of positive cells, which does not discriminate between NHL subtypes, we quantified the intensity of CAM expression using flow cytometry. Apart from CD49d the expression of all these CAMs was statistically different among the NHL subtypes as defined by the REAL classification. Low grade NHL-small lymphocytic, follicular and mantle cell lymphoma--which are derived from quiescent cells and show an indolent disease course, expressed low levels of CAMs. Conversely, high grade NHL-diffuse large cell lymphoma--which are derived from proliferating cells and are clinically aggressive, expressed high levels of CAMs. These results indicate that in malignant NHL B cell tumour growth and clinical aggressiveness may be related to the adhesive capacities of the tumour cells.

Differentiation of antitumor-specific cytotoxic T lymphocytes from autologous tumor infiltrating lymphocytes in non-Hodgkin's lymphomas

The present study describes a new culture protocol allowing the activation and proliferation of autologous tumor infiltrating T lymphocytes (TIL), and the generation of antitumor specific CTL in non-Hodgkin's lymphoma (NHL). Cells from eight patients with indolent NHL were used. We performed 3-week co-cultures of TIL with irradiated autologous malignant B cells in the presence of low doses of IL-1beta, IL-2 and IL-12. The proliferation, phenotype and cytotoxicity, and antitumor specificity of T cells recovered were studied. T-cell clonality was analyzed using TCRgamma gene rearrangement amplification by a multiplex PCR. Under these culture conditions, TIL proliferated, and the CD8+ T lymphocytes that were in a minority at the beginning of the culture increased dramatically in 6 out of 8 cases. In two cases, CD4+ T lymphocytes expanded. We showed that an oligoclonal selection of reactive T cells occurred in culture. Specific cytotoxicity developed against autologous malignant B cells in the 6 cases where there was an expansion of CD8+ T lymphocytes. Inhibition experiments performed with mAb directed against HLA class I and II molecules, CD4, CD8 and TCRgammadelta showed that the cytotoxic effector cells were CD8+ T lymphocytes probably expressing TCRalphabeta+. Cytokine secretion was analyzed in culture medium, and we detected significant levels of IFN-gamma, TNF-alpha, and IL-10 and no IL-4 (except in one case). Our results demonstrate that memory T cells from lymphoma patients can be amplified and differentiated into antitumor cytotoxic cells using a combination of the cytokines IL-1beta, IL-2, and IL-12 in association with non modified tumor cells.

Functional expression of CD80 and CD86 allows immunogenicity of malignant B cells from non-Hodgkin's lymphomas

We analyzed the accessory function of malignant B cells from non-Hodgkin's lymphomas (NHLs). Among the 70 samples of malignant B cells included, four patterns of expression of the costimulatory molecules CD80 and CD86 were distinguished (+/+, +/-, -/+ and -/-). In two-thirds of the cases, CD80, CD86, or both were expressed. To investigate the relevance of these molecules for tumor immunogenicity, mixed lymphocyte reactions (MLR) were performed with allogeneic responding T cells and malignant B cells from nine NHL patients. Regardless of the level of expression of CD80 and CD86, significant proliferation was induced in the responder cells. The addition of monoclonal antibodies directed against CD80 and CD86 at the beginning of MLR almost completely inhibited this proliferation. We show that, during MLR, a high level of expression of CD80 and CD86 was induced in NHL B cells. Thus, cooperation between responding and stimulator cells seems to occur during MLR, allowing induction of optimal accessory function of B cells. We investigated whether malignant B cells cultured with CD40-L-transfected L cells in the presence of IL-4 could augment their antigen-presenting cell (APC) functions. The culture of NHL B cells in this sytem induced strong upregulation of the expression of CD80 and CD86 as well as other molecules involved in accessory cell functions (HLA class I, CD54, and CD58). In half of the cases, this activation resulted in enhanced proliferation of allo-T cells as compared to the proliferation induced by nonactivated malignant B cells. Our results show that NHL B cells are able to express functional CD80 and CD86 and to be fully competent APC. This suggests that the absence of an efficient T cell-mediated antitumor response in vivo is not related to a deficiency in the APC functions of malignant B cells.

Heterogeneity and immunochemical properties of anti-beta2-glycoprotein I autoantibodies

Most anticardiolipin antibodies (ACA) associated with antiphospholipid syndrome (APS) are directed against epitopes expressed on beta2-glycoprotein I (beta2GPI). Despite a good correlation between standard ACA assays and those using purified human beta2GPI as the sole antigen, some sera from APS patients only react in the latter. This is indicative of heterogeneity in anti-beta2GPI antibodies. To characterize their reactivity profiles, human and bovine beta2GPI were immobilized on gamma-irradiated plates (beta2GPI-ELISA), plain polystyrene precoated with increasing cardiolipin concentrations (CL/beta2GPI-ELISA), and affinity columns. Fluid-phase inhibition experiments were also carried out with both proteins. Of 56 selected sera, restricted recognition of bovine or human beta2GPI occurred respectively in 10/29 IgA-positive and 9/22 IgM-positive samples, and most of the latter (8/9) were missed by the standard ACA assay, as expected from a previous study. Based on species specificity and ACA results, IgG-positive samples (53/56) were categorized into three groups: antibodies reactive to bovine beta2GPI only (group I) or to bovine and human beta2GPI, group II being ACA-negative, and group III being ACA-positive. The most important group, group III (n = 33) was characterized by (i) binding when beta2GPI was immobilized on gamma-irradiated polystyrene or cardiolipin at sufficient concentration (regardless of beta2GPI density, as assessed using 125I-beta2GPI); (ii) and low avidity binding to fluid-phase beta2GPI (Kd in the range 10(-5) M). In contrast, all six group II samples showed (i) ability to bind human and bovine beta2GPI immobilized on non-irradiated plates; (ii) concentration-dependent blockade of binding by cardiolipin, suggesting epitope location in the vicinity of the phospholipid binding site on native beta2GPI; (iii) and relative avidities approximately 100-fold higher than in group III. Group I patients were heterogeneous with respect to CL/beta2GPI-ELISA and ACA results (6/14 scored negative), possibly reflecting antibody differences in terms of avidity and epitope specificity. Affinity fractionation of 23 sera showed the existence, in individual patients, of various combinations of antibody subsets solely reactive to human or bovine beta2GPI, together with cross-species reactive subsets present in all samples with dual reactivity namely groups III and II, although the latter antibodies were poorly purified on either column. Therefore, the mode of presentation of beta2GPI greatly influences its recognition by anti-beta2GPI antibodies with marked inter-individual heterogeneity, in relation to ACA quantitation and, possibly, disease presentation and pathogenesis.

Tumor B cells from non-Hodgkin's lymphoma are resistant to CD95 (Fas/Apo-1)-mediated apoptosis

Apoptosis mediated by the CD95 (Fas/Apo-1) molecule plays a crucial role in the regulation of the B-cell immune response. In this study, we examined the function of the CD95 antigen in B-cell-derived non-Hodgkin's lymphoma (NHL), a malignant disease of mature B cells. Membrane CD95 molecules were found to be constitutively expressed in a large number of NHL, including mantle cell (MCL, n = 10), lymphocytic (LCL, n = 10), follicular (FL, n = 11), and diffuse large cell lymphoma (DLCL, n = 9) with, however, different levels of intensity. Indeed, the levels of CD95 were low in MCL and LCL as compared with FL and DLCL. However, regardless of the intensity of expression, CD95 triggering with anti-CD95 monoclonal antibody (MoAb) did not induce apoptosis of lymphoma B cells, while these cells underwent apoptosis after irradiation or staurosporine treatment. Further experiments were then performed to address whether apoptosis could be restored by B-cell activation via CD40 cross-linking. We showed that CD40 engagement in the presence of interleukin (IL)-4 was more effective than CD40 engagement alone in upregulating the CD95 antigen and induced CD95-mediated cell death in nontumoral B cells. Concerning malignant B cells, CD40 ligation in the presence of IL-4 strongly increased CD95 expression, but did not markedly increase CD95-induced apoptosis. Furthermore, using cytotoxic T cells, we showed that CD95L was also ineffective in inducing apoptosis in lymphoma B cells, whereas these cells were killed by the perforin pathway. Our findings suggest that the CD95-mediated cell death pathway is altered in malignant cells from the NHL we tested. This could be a mechanism allowing lymphoma B cells to escape from immune regulation.

Relationships between susceptibility to LAK cell-mediated lysis, conjugate formation and expression of adhesion molecules in B-cell derived non-Hodgkin's lymphomas

Adoptive immunotherapy with LAK cells has been investigated for the treatment of B-cell-derived lymphomas, but only a few significant tumor regressions were obtained. In order to explain this refractory state, the sensitivity to normal LAK-mediated lysis of 30 non-Hodgkin's lymphoma (NHL) malignant B-cells was determined using flow cytofluorimetry. A large heterogeneity was found, and we report a close correlation (p < 0.001) between the extent of lysis of malignant B-cells and their ability to form conjugates with LAK cells; which is the first step in LAK-mediated cytolysis. The levels of expression of HLA class I molecules, LFA-1 (CD11a/CD18), CD54 and CD58 were also studied and found to be expressed very heterogeneously. CD54 expression on malignant B-cells plays a major role in the initial conjugate formation with LAK cells (p < 0.001), and this was confirmed by inhibition experiments. Our results suggest that a weak expression of CD54 could constitute one mechanism by which NHL tumor B-cells escape natural immune surveillance and resist LAK cells immunotherapies.

False-negative results in anti-HLA antibody detection by Sangstat ELISA: complement dependent cytotoxicity is not yet obsolete

Although ELISA on purified HLA molecules for detecting anti-HLA antibody (P-S ELISA) does detect some antibodies previously missed by the conventional complement dependent cytotoxicity method (C Cytotox), HLA ELISA should not fail to detect antibodies already detected by the conventional reference method to be able to make C Cytotox obsolete and to replace it in routine testing. Among 40 selected sera, 8 false-negative reactions were observed in P-S ELISA. These sera were reanalyzed blind in two laboratories and found to contain non-IgM, warm anti- HLA antibodies. These antibodies were directed in 4 cases against an HLA molecule expressed on a kidney transplant previously rejected by the subject. These antibodies, if missed, would have been potentially harmful in kidney transplantation. Thus P-S ELISA can't yet replace C Cytotox in routine anti-HLA class I detection. The cost/benefit ratio of P-S ELISA as a second-line test remains to be investigated.

Species specificity of anti-beta 2 glycoprotein I autoantibodies and its relevance to anticardiolipin antibody quantitation

Some patients suspected of having antiphospholipid antibody syndrome (APS) were found to be positive for anti-beta 2 glycoprotein I (beta 2GPI) antibodies despite negative results for antibodies to cardiolipin (ACA). Since the major source of beta 2GPI in the ACA assay is animal (usually bovine) serum, we studied the influence on ACA quantitation of the species specificity of anti-beta 2GPI antibodies from patients with various autoimmune disorders, mostly systemic lupus erythematosus and primary APS. Ninety-seven sera were selected based on IgG (n = 76) or IgM (n = 64) positivity by ELISA using gamma-irradiated plates coated with human or bovine purified beta 2GPI. A higher proportion of IgM (43.7%) than IgG (7.9%) reacted to human, but not bovine, beta 2GPI. Furthermore, from the samples reactive to both proteins, the ratio of antibody level against bovine to that against human beta 2GPI was 1.08 +/- 0.58 for IgG and 0.58 +/- 0.3 for IgM (p < 10(-5)). IgG and IgM ACA were detected in 78 and 40 sera, respectively; concordance between the two ELISAs for ACA and anti-beta 2GPI antibodies was 94% for IgG and 75% for IgM. Out of 28 IgM showing recognition restricted to human beta 2GPI, 21 were missed by the ACA assay, possibly because of lower concentrations of beta 2GPI in those patients' sera. The antibody reactivity pattern towards human and bovine beta 2GPI of individual sera showed no variation with time and was related to the relative antibody avidity for each protein. A murine anti-human beta 2GPI monoclonal antibody, 9G1, that cross-reacts with bovine beta 2GPI, competed to a large extent with the patients' anti-beta 2GPI antibody binding sites whatever isotype involved or protein recognized. Therefore, anti-beta 2GPI antibodies of IgM isotype display a marked preference for human compared to bovine beta 2GPI responsible for frequent inconsistencies in the ACA assay.

HCV-Infection in blood donors: association between anti-HCV core IgM antibodies and serum HCV RNA

Among 47 blood donors tested positive with HCV EIA 2.0 Abbott, 27 (57.4%) also reacted with four ¿third-generation' EIAs. The presence of anti-HCV antibodies was confirmed with 3 different immunoblot assays in 16 of 27 sera (34.0%) while 10 samples (21.3%) had indeterminate profile with antibodies usually directed against structural core antigen. Anti-HCV core IgM response was found in 12 of 47 sera (25.5%) and HCV viremia detected by the polymerase chain reaction (PCR) procedure was observed in 15 samples (31.9%). A comparative study of the different markers confirmed a good correlation between a strong antibody response in EIAs and immunoblot assays and the presence of HCV RNA in the serum; only 2 immunoblot indeterminate samples were PCR positive. An association was observed between IgM antibodies against "core' epitopes and HCV RNA carriage: all IgM-positive sera were found positive by PCR. However, the direct detection of viral genome remains the best method for identifying HCV carriers in the blood donor population.

Malignant B lymphocytes from non-Hodgkin's lymphoma induce allogeneic proliferative and cytotoxic T cell responses in primary mixed lymphocyte cultures: an important role of co-stimulatory molecules CD80 (B7-1) and CD86 (B7-2) in stimulation by tumor cells

We analyzed the stimulating capacities of malignant B cells from non-Hodgkin's lymphomas (NHL) to induce an allogeneic response in primary mixed lymphocyte reaction (MLR). T cells purified from a single healthy donor (KS) were used to compare the responses induced by either malignant or hyperplastic cells. Malignant B cells induced strong proliferation of KS cells independently of their level of expression of adhesion molecules. The KS cells after MLR were predominantly CD3+, CD25+, HLA-DR+, Ki67+ and CD45RO+ T cells, and the CD4/CD8 ratio was heterogeneous (from 0.8 to 2.7). To investigate the role of co-stimulatory molecules CD80 and CD86 for the stimulatory capacities of B cells, the expression of both molecules was analyzed before and during the MLR. Most fresh malignant B cells were negative for CD80 and CD86, whereas co-cultured B cells expressed high levels of both molecules. This expression was crucial for T cell proliferation, since monoclonal antibodies directed against CD80 and CD86 completely abrogated the MLR. We also report that KS responding cells at the end of co-culture were able to lyse fresh B cells used as stimulator cells to different extents (from 10 to 51%), and the level of lysis was enhanced after PMA activation of the target cells. Inhibition experiments using CD8 and CD4 mAb showed that effector cells were mainly CD8+. This report is the first to describe the accessory function of human malignant B cells from NHL and their sensitivity to lysis mediated by CD8+ T cells, and suggests new strategies for the development of antitumor immunity in NHL.

Development of an ELISA for autoantibodies to prothrombin showing their prevalence in patients with lupus anticoagulants

Some lupus anticoagulants (LA) have been shown to be directed against phospholipid-bound prothrombin. While developing an ELISA to detect anti-prothrombin autoantibodies in patient serum or plasma, no or very low signal was observed using human prothrombin immobilized on plain polystyrene plates. In contrast, the same LA-positive samples bound specifically to prothrombin coated on gamma-irradiated plates, depending on the radiation dose, in the absence of added calcium and phospholipid. Optimization of the assay required the addition of 0.1% Tween 20 to the buffers. Antibody specificity for immobilized prothrombin was ascertained by competition using liposome-bound prothrombin, since fluid-phase prothrombin competed poorly. Seventy-seven of 139 patients (55.4%) with LA related to a variety of underlying diseases possessed anti-prothrombin antibodies (27 IgG, 35 IgM and 15 both isotypes), either isolated or more often associated with anti-beta 2 glycoprotein I (beta 2GPI) antibodies. These included 67-71% of the patients with systemic lupus erythematosus and related disorders, primary antiphospholipid antibody syndrome or drug-induced LA (autoimmune groups), but only 19-20% of those with infection or malignancy (p < 0.001). As previously shown for anti-beta 2GPI antibodies, IgG2 was the predominant IgG subclass reactive with prothrombin. Thus, autoimmune patients with LA have a high incidence of antibodies to beta 2GPI and prothrombin, the binding of which could similarly require high antigen density and/or exposure of cryptic epitopes resulting from protein interaction with an irradiated (i.e. more anionic) polystyrene surface.

Autotumour reactive T-cell clones among tumour-infiltrating T lymphocytes in B-cell non-Hodgkin's lymphomas

Seventy-three T-cell clones (TCC) were established from tumour-infiltrating lymphocytes-T (TIL-T) derived from lymph nodes involved by B-cell non-Hodgkin's lymphomas (B-NHL) in nine patients with different histological subtypes and clinical stages. 40 TCC (55%) expressed the CD25 Ag and were also able to proliferate in the presence of irradiated autologous B-NHL cells. Among them, 23 autotumour (AuTu) proliferative TCC were found not to proliferate to autologous EBV-transformed B-cell lines, indicating that the proliferative reactivity of these TCC was preferentially directed at autologous B-NHL cells. Tested against autologous B-NHL cells, only three AuTu proliferative TCC (CD8+) showed a significant level of cytotoxicity (specific lysis > 15%). In blocking experiments, the AuTu proliferative reactivity of three TCC from one patient was strongly inhibited by anti-DR and anti-DQ mAbs, whereas that of three TCC from another patient was not affected by either anti-MHC class I or class II (DR, DP, DQ) mAbs. These findings suggest that the recognition of autologous B-NHL cells by AuTu proliferative TCC may occur through MHC-restricted as well as MHC-unrestricted mechanisms.

Beneficial effect of one HLA haplo- or semi-identical transfusion versus three untyped blood units on alloimmunization and acute rejection episodes in first renal allograft recipients

Acute allograft rejection is the major risk factor of renal function decline and graft loss. Beside histocompatibility matches and pharmacological immunosuppression, blood transfusion is empirically used to detect responder subjects and to induce immune tolerance. Alloimmunization associated with blood transfusions readily detected by anti-HLA antibodies could induce acute vascular rejection episodes during the early period after grafting. Our open prospective study was aimed at analyzing the 1 year follow-up of 105 successive first cadaver renal transplant recipients according to the transfusion protocol as assessed by anti-HLA antibody production, acute rejection episodes, and graft survival. Our conventional transfusion protocol involved 3 nonphenotyped blood transfusions set up at least 20 days before grafting in a control cohort (group A) and was compared with a single pretransplant HLA haplo- or semi-identical blood transfusion in a successive group of patients (group B). Our results suggest that both protocols were associated with similar 1-year graft survivals (> 96% in both groups) and number of patients experiencing rejection episodes (20.7% in group A; 9.6% in group B; P NS). HLA haplo- or semi-identical transfusion was significantly beneficial in naive patients without previous alloantigen contact by pregnancy or blood transfusions during dialysis. Naive patients in group B did not develop post-transfusion anti-HLA antibodies compared to naive patients in group A (16.6%; P < 0.001), and they experienced significantly less acute rejection episodes (2.7%) compared to group A naive patients (20.8%; P = 0.02).

Neutrophil activation by anti-beta 2 glycoprotein I monoclonal antibodies via Fc gamma receptor II

Murine monoclonal antibodies (mAbs) to human beta 2-glycoprotein I (beta 2GPI), a plasma protein required for the binding of some antiphospholipid antibodies, have been shown to possess lupus anticoagulant properties and to activate platelets via Fc gamma receptor (Fc gamma R) crosslinking. Here we investigated their ability to induce polymorphonuclear leukocyte (PMN) functional responses. The six mAbs (IgG1 isotype) tested in combination with beta 2GPI led to a concentration-dependent activation of human PMNs as appreciated by granule release, H2O2 production, and cytosolic Ca2+ increase. This activation process was accompanied by the enhancement of PMN-mediated heparan sulfate loss from the endothelial cell line EA.hy 926 without evidence for cell lysis or detachment. F(ab')2 fragments of one of the mAbs bound to PMNs in a beta 2GPI-dependent manner but were devoid of activating effects. Carbamylated beta 2GPI was unable to mediate PMN-antibody binding and subsequent activation. In addition, cationization of beta 2GPI or removal of its sialic acid groups led to higher efficiency in binding to the PMN surface and triggering activation in comparison with the untreated protein. Thus, the process of PMN activation depends on mAb binding to these cells through both Fab (via beta 2GPI) and Fc domains, as confirmed by the suppression of all responses upon treatment with an anti-Fc gamma RII, but not anti-Fc gamma RIII, antibody. Our data suggest a model of cellular activation by beta 2GPI-dependent antiphospholipid antibodies.

Evaluation of monoclonal antibodies with specificity for the human platelet HPA-1 allotypes

Two mouse monoclonal antibodies have been characterized. Both antibodies specifically recognized the amino acid sequences which are responsible for the presence of the HPA-1a and HPA-1b alloantigens at the surface of human platelet. The monoclonality allied with an exquisite specificity of these antibodies allow a perfect typing of platelet HPA-1 status. A fast and reliable Elisa assay which fulfills all the needs and requirements of hematology laboratories has been set up and is described here. The Elisa assay has been tested on a population of 689 blood donors. The results agreed with the known phenotypic frequencies of the HPA-1 alloantigens.

DNA typing: an important step forward? Collaborative Transplant Study

In a collaborative project which was supported by 96 transplant centers, DNA typing of HLA-DR antigens was carried out on over 7,000 transplant donors and recipients at 8 participating laboratories. Approximately 25% of the individuals were found to have been typed incorrectly by serological means. An analysis of over 2,500 first cadaver kidney transplants showed a significant correlation of matching for the HLA-DR antigens in transplants where the serological typing was confirmed by DNA typing. In transplants where the serological typing was found to be incorrect, the analysis of serological HLA-DR mismatches resulted in no correlation with graft outcome whereas a significant correlation was found when the corrected DNA typed HLA-DR antigens were analyzed. Transplants which had been reported to the Collaborative Transplant Study based on serological typing as matched for HLA-A, -B, -DR or HLA-B, -DR were found to have a superior graft survival rate only if HLA-DR compatibility was confirmed by DNA typing.

CD45RA expression by CD4 T lymphocytes in tumors invaded by B-cell non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD)

Little is known about the role of tumor infiltrating T lymphocytes (TIL-T) in the pathogenesis of malignant diseases and collaboration between normal and malignant cells has not yet been proved. In the present work, we have investigated whether immune T lymphocytes exist in tumors invaded by B-cell non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD). Therefore, we have studied the reactivity of the CD45RA monoclonal antibody, which discriminates between naive and memory CD4 T lymphocytes. Our results showed far lower percentages of CD4+ CD45RA+ in malignant lymphoma (30.3 +/- 15.0% in B-cell NHL, and 37.4 +/- 18.6% in HD) than in reactive hyperplasia (54.7 +/- 13.2%), leading to the conclusion of an accumulation of immune cells in tumor microenvironment. A further heterogeneity in the relative proportion of naive and memory TIL-T was also observed within lymphoma (range: 11 to 68% in B-cell NHL, 5 to 69% in HD). In B-cell NHL, it was related to histological features, as documented by the Kiel classification (P = .028), and to a stronger extent to cytological characteristics analysed with the Grenoble classification (P less than .0001): class 1 NHL, which are essentially indolent NHL displayed lower naive cells (22.2 +/- 7.4%) than class 3 NHL, which are more aggressive (40.1 +/- 16.1%). Among the monoclonal antibodies (mAb) defining the B-cell clone phenotype or activation state (CD19, CD20, CD21, CD22, CD23, CD24, CD5, CD10, CD11a, and Ki67), only CD23 (P = .0003) and Ki67 (P = .0007) revealed statistical association with the percentage of naive CD4 lymphocytes. No correlation could be demonstrated with the proportion of whole TIL-T, activated CD3 DR TIL-T, or CD4 subset.

Membrane cell permeabilization with saponin and multiparametric analysis by flow cytometry

Saponin, a detergent like molecule, can permeabilize cell membranes without destroying them, and thus can be used for the detection of intracellular antigens on intact cells with a flow cytometer. First experiments were reported that demonstrated the detection of intracytoplasmic antigens such as intermediate filaments and CD3 in T acute lymphoblastic leukemia (ALL). Further experiments were also performed to prove that intranuclear structures were equally accessible: dyes such as propidium iodide (PI) and monoclonal antibodies (mAb) such as Ki67 could penetrate the nucleus and lead to the analysis of DNA content and to the discrimination between the different cell cycle phases (G0, G1, S, G2-M). This rapid and sensitive method retained sufficient integrity of cells being treated to enable differentiation of cell types on the basis of morphology. Furthermore, it did not alter membrane expression of most antigens. Therefore, it was of particular interest for multiparametric analysis, especially for simultaneous study of membrane and intracellular structures.

Translocation t(3;22)(q23;q11) in three patients with diffuse large B cell lymphoma

In our series of 134 patients with a diagnosis of non-Hodgkin's lymphoma (NHL) and clonal chromosomal abnormalities, three were found to show an identical t(3;22)(q28;q11) translocation. All were old patients with isolated lymphadenomegaly and diffuse large noncleaved cell lymphoma. All expressed a B cell immunophenotype, and all entered a complete remission when treated with aggressive chemotherapy. This translocation could, therefore, delineate a particular subtype of diffuse large cell NHL.

T lymphocytes from invaded lymph nodes in patients with B-cell-derived non-Hodgkin's lymphoma: reactivity toward the malignant clone

Tumor-infiltrating T lymphocytes (TIL-T) are always present in B-cell-derived non-Hodgkin's lymphoma (NHL). In this investigation, we explored the possibility that collaboration might exist between these cells. TIL-T were isolated from 39 lymph nodes of patients with NHL. In most of the cases, few of them (less than 10%) possessed surface activation receptors CD25 or OKT9. In 80% of the cases, they proliferated in response to recombinant interleukin-2 (rIL-2), but the degree of proliferation was often low as compared with control populations. The influence of irradiated autologous malignant cells on the TIL-T proliferation in response to rIL-2 (40 U/mL) was also investigated: in 38% of the cases, this proliferation was not modified (group O), and in 41% it was higher (group +) and in 21% it was lower (group -). The mechanism of this immune response (specific or not) is not elucidated at present. The definition of these groups was statistically correlated with different parameters of the disease: (1) percentage of TIL-T was higher in group + (44% +/- 17%) than in group O (31% +/- 18%) and group - (24% +/- 15%); (2) B-cell proliferation in centrofollicular lymphomas was more frequently nodular or nodular and diffuse in group + (83%) and O (55%) than in group - (0%); (3) low-grade malignancies in the Working Formulation were more frequent in group + (75%) than in group O (60%) or group - (12%); (4) favorable prognosis evaluated with the Grenoble cytologic classification was more frequent in group + and O (87%) than in group - (12%); (5) actuarial survival curves showed a significantly better prognosis for patients in group +.

Multicentric reticulohistiocytosis: a case with enhanced interleukin-1, prostaglandin E2 and interleukin-2 secretion

We describe a 47-year-old woman with multicentric reticulohistiocytosis. While the disease was in remission without therapy, interleukin-1 and prostaglandin E2 secretions by adherent cells was increased as well as interleukin-2 secretion by peripheral mononuclear cells. This suggests that macrophages play an essential role in the pathogenesis of this disease.

[Malignant non-Hodgkin's lymphoma associated with a serum monoclonal immunoglobulin]

Among the 394 non-Hodgkin's lymphomas (NHL) observed at our hospital over a thirteen year period, we have found 17 associated monoclonal gammopathies (4.3%). Fourteen gammopathies could be correlated to the lymphoid tumor due to a study of immunological membrane markers and to the comparative evolution of the disease and the monoclonal gammopathy. Two different groups could be distinguished: Six patients out of the fourteen studied (43%) had a gammopathy similar to the surface immunoglobulins of the tumour lymphoid cells. Seven of the seventeen showed, after treatment, a parallel evolution between the tumor and the gammopathy. This originates directly from the tumoral secretion and deserves to be classified among the B lymphoid excretory tumors. Six were IgM and one was IgG. Eight of the fourteen patients studied (57%) did not show any immunological relation between the lymphoma and the monoclonal gammopathy. The evolutions (10 of the 17 patients) of the tumor and of the gammopathy were independent. Among the eleven gammopathies (1 double gammopathy), 5 were IgG, 4 were IgA and 2 were IgM. The incidence of these gammopathies related to the total group tf lymphomas is 2.5%. Given the age of these patients, the association seems fortuitous.