Production of monoclonal antibodies and development of a quantitative immuno-polymerase chain reaction assay to detect and quantify recombinant Glutathione S-transferase

GST-tagged proteins are important tools for the production of recombinant proteins. Removal of GST tag from its fusion protein, frequently by harsh chemical treatments or proteolytic methods, is often required. Thus, the monitoring of the proteins in tag-free form requires a significant effort to determine the remnants of GST during purification process. In the present study, we developed both a conventional enzyme-linked immunosorbent assay (ELISA) and an immuno-polymerase chain reaction (IPCR) assay, both specific for detection of recombinant GST (rGST). rGST was expressed in Escherichia coli JM109, using a pGEX4T-3 vector, and several anti-rGST monoclonal antibodies were generated using hybridoma technology. Two of these were rationally selected as capture and detection antibodies, allowing the development of a sandwich ELISA with a limit of detection (LOD) of 0.01 μg/ml. To develop the rGST-IPCR assay, we selected "Universal-IPCR" format, comprising the biotin-avidin binding as the coupling system. In addition, the rGST-IPCR was developed in standard PCR tubes, and the surface adsorption of antibodies on PCR tubes, the optimal neutravidin concentrations, the generation of a reporter DNA and the concentration effect were studied and determined. Under optimized assay conditions, the rGST-IPCR assay provided a 100-fold increase in the LOD as well as an expanded working range, in comparison with rGST-ELISA. The proposed method exhibited great potentiality for application in several fields in which measurement of very low levels of GST is necessary, and might provide a model for other IPCR assays.

Hybridoma Technology

The generation of hybridoma cell lines by the fusion of splenocytes from immunized mice with immortal myeloma cells is a well-established method for the production of monoclonal antibodies. Although other methods have emerged as an effective alternative for the generation of monoclonal antibodies, the use of hybridoma technology remains a viable technique that is accessible to a wide number of laboratories that perform basic cell biological research. Hybridoma technology represents a relatively simple procedure at minimal cost for the continuous production of native whole immunoglobulins. This chapter will describe the materials and methodologies needed for the successful generation of monoclonal antibody (mAb)-producing hybridoma cell lines against target antigens.

Label-free hybridoma cell culture quality control by a chip-based impedance flow cytometer

Impedance flow cytometry (IFC) was evaluated as a possible alternative to fluorescence-based methods for on-line quality monitoring of hybridoma cells. Hybridoma cells were cultured at different cell densities and viability was estimated by means of IFC and fluorescence-based flow cytometry (FCM). Cell death was determined by measuring the impedance phase value at high frequency in low conductivity buffer. IFC data correlate well with reference FCM measurements using AnnexinV and 7-AAD staining. Hybridoma cells growing at different densities in cell culture revealed a density-dependent subpopulation pattern. Living cells of high density cultures show reduced impedance amplitudes, indicating particular cellular changes. Dead cell subpopulations become evident in cultures with increasing cell densities. In addition, a novel intermediate subpopulation, which most probably represents apoptotic cells, was identified. These results emphasize the extraordinary sensitivity of high frequency impedance measurements and their suitability for hybridoma cell culture quality control.

Control of late apoptotic events by the p38 stress kinase in L-glutamine-deprived mouse hybridoma cells

L-Glutamine (Gln) starvation rapidly triggers apoptosis in Sp2/0-Ag14 (Sp2/0) murine hybridoma cells. Here, we report on the role played by the stress-activated kinase p38 mitogen-activated protein kinase (MAPK) in this process. p38 activation was detected 2 h after Gln withdrawal and, although treatment with the p38 inhibitor SB203580 did not prevent caspase activation in Gln-starved cells, it reduced the occurrence of both nuclear condensation/fragmentation and apoptotic body formation. Similarly, transfection of Sp2/0 cells with a dominant negative p38 MAPK reduced the incidence of nuclear pyknosis and apoptotic body formation following 2 h of Gln starvation. Gln withdrawal-induced apoptosis was blocked by the overexpression of the anti-apoptotic protein Bcl-xL or by the caspase inhibitor Z-VAD-fmk. Interestingly, Bcl-xL expression inhibited p38 activation, but Z-VAD-fmk treatment did not, indicating that activation of this MAPK occurs downstream of mitochondrial dysfunction and is independent of caspases. Moreover, the anti-oxidant N-acetyl-l-cysteine prevented p38 phosphorylation, showing that p38 activation is triggered by an oxidative stress. Altogether, our findings indicate that p38 MAPK does not contribute to the induction of apoptosis in Gln-starved Sp2/0 cells. Rather, Gln withdrawal leads to mitochondrial dysfunction, causing an oxidative stress and p38 activation, the latter contributing to the formation of late morphological features of apoptotic Sp2/0 cells.

Inhibition of T cell response to native low-density lipoprotein reduces atherosclerosis

Immune responses to oxidized low-density lipoprotein (oxLDL) are proposed to be important in atherosclerosis. To identify the mechanisms of recognition that govern T cell responses to LDL particles, we generated T cell hybridomas from human ApoB100 transgenic (huB100(tg)) mice that were immunized with human oxLDL. Surprisingly, none of the hybridomas responded to oxidized LDL, only to native LDL and the purified LDL apolipoprotein ApoB100. However, sera from immunized mice contained IgG antibodies to oxLDL, suggesting that T cell responses to native ApoB100 help B cells making antibodies to oxLDL. ApoB100 responding CD4(+) T cell hybridomas were MHC class II-restricted and expressed a single T cell receptor (TCR) variable (V) beta chain, TRBV31, with different Valpha chains. Immunization of huB100(tg)xLdlr(-/-) mice with a TRBV31-derived peptide induced anti-TRBV31 antibodies that blocked T cell recognition of ApoB100. This treatment significantly reduced atherosclerosis by 65%, with a concomitant reduction of macrophage infiltration and MHC class II expression in lesions. In conclusion, CD4(+) T cells recognize epitopes on native ApoB100 protein, this response is associated with a limited set of clonotypic TCRs, and blocking TCR-dependent antigen recognition by these T cells protects against atherosclerosis.

Fusion induced reversal of dendritic cell maturation: an altered expression of inflammatory chemokine and chemokine receptors in dendritomas

Dendritic cell-mediated cancer immunotherapy employs several ways to engage tumor antigens. We have demonstrated in both pre-clinical animal studies and early clinical trials that dendritomas, highly purified hybrids between dendritic cells (DC) and tumor cells, are superior activators of anti-tumor immunity. It has been argued, however, that DC vaccines may be dysfunctional in lymph node migration. In the present study we examined inflammatory chemokine and chemokine receptor expression as well as other maturation induced genes in dendritomas produced from either immature or mature DCs in order to shed light on their capacity to migrate from injection sites to draining lymph nodes and elicit an appropriate immune response. RNA microarray analysis was used to identify gene expression profiles for inflammatory chemokines and receptors and other maturation induced genes within dendritomas, lysate-pulsed dendritic cells, immature DCs and mature DCs. Gene regulation was confirmed with relative quantification, real-time RT-PCR in a separate experiment. We found that fusion of immature DCs to tumor cells initiates maturation with respect to inflammatory chemokines, chemokine receptors and other maturation induced genes in a similar pattern as LPS matured DCs. Interestingly, we saw a reversed gene profile when mature DCs were fused to tumor cells. LPS matured DCs displayed the chemokine repertoire expected with DC maturation; however, once fused to tumor cells, these chemokines and other maturation induced genes reverted to levels comparable to immature DCs. It appears that mature DCs used for dendritoma production result in a de-mature genotype. Our results indicate that dendritomas from immature DC/tumor cell fusions may be more effective in migration from injection site to draining lymph nodes and, therefore, would be more effective in stimulating anti-tumor immunity.

The flavonoid rutin but not the alkaloid arborinine induces apoptosis in a B-cell hybridoma cell line

The effects of arborinine, an alkaloid extracted from Erthela bahiensis and of rutin, a flavonoid obtained from Dimorphandra mollis (Benth.), Brazilian medicinal plants, on the viability and function of a murine B-cell hybridoma as a tumor model were investigated. The flavonoid rutin at 50 microM induced an increase in the number of apoptotic cells of one- to fivefold and reductions in cellular proliferation and monoclonal antibody production. Less but still significant necrosis was also induced by rutin under the same experimental conditions. On the other hand, the alkaloid arborinine exerted no significant effects on the studied parameters.

Hyperosmotic Stress in Murine Hybridoma Cells: Effects on Antibody Transcription, Translation, Posttranslational Processing, and the Cell Cycle

Mechanisms for increased antibody production in batch cultures of murine hybridoma cells in response to hyperosmotic stress were investigated. The rates of immunoglobulin transcription and protein translation and posttranslational processing were determined in control and hyperosmotic cultures. Changes in immunoglobulin transcription played a minor role in the increase in antibody production in response to hyperosmotic stress. In contrast, protein translation increased substantially in response to osmotic stress. However, the antibody translation rate remained relatively constant after correcting for the overall increase in protein translation. Cell size and intracellular antibody pool also increased in response to hyperosmolarity. The intracellular antibody pool increased proportionately with the increase in cell size, indicating that hyperosmotic cultures do not selectively increase their intracellular antibody population. Changes in cell cycle distribution in response to osmotic stress and the relationship between the cell cycle and antibody production were also evaluated. Hyperosmotic stress altered the cell cycle distribution, increasing the fraction of the cells in S-phase. However, this change was uncorrelated with the increase in antibody production rate. Immunoglobulin degradation was relatively low ( approximately 15%) and remained largely unchanged in response to hyperosmotic stress. There was no apparent increase in immunoglobulin stability as a result of osmotic stress. Antibody secretion rates increased approximately 50% in response to osmotic stress, with a commensurate increase in the antibody assembly rate. The rate of transit through the entire posttranslational processing apparatus increased, particularly for immunoglobulin light chains. The levels of endoplasmic reticulum chaperones did not increase as a fraction of the total cellular protein but were increased on a per cell basis as the result of an increase in total cellular protein. A difference in the interactions between the immunoglobulin heavy chains and BiP/GRP78 was observed in response to hyperosmotic conditions. This change in interaction may be correlated with the decrease in transit time through the posttranslational pathways. The increase in the posttranslational processing rate appears to be commensurate with the increase in antibody production in response to hyperosmotic stress.

[Growth and differentiation of cell hybrids obtained by fusing mouse PCC4azal teratocarcinoma cells and mouse spleen cells under different in vitro culture conditions]

Cell hybrids obtained by fusing mouse PCC4azal teratocarcinoma cells and spleen cells induced to proliferation and treated with the demethylating agent 5-azacytidine prior to fusion are described. The obtained hybrids demonstrated no expression of T lymphocyte marker genes CD11 and CD45, which indicates possible somatic nucleus reprogramming by factors present in teratocarcinoma cells. Irrespective of culture conditions, cell hybrids demonstrated a relatively stable chromosome number: they lost on average no more than four chromosomes after 30 passages. Culturing in medium containing hypoxanthine, aminopterin, and thymidine (selective conditions) decreased the differentiation capacity of cell hybrids compared to nonselective conditions, which is likely due to the inhibition of their metabolism. For the first time, teratocarcinoma cell hybrid differentiation into cardiomyocytes under the influence of DMSO has been demonstrated in vitro.

The metastatic T-cell hybridoma antigen/P-selectin glycoprotein ligand 1 is required for hematogenous metastasis of lymphomas

Using variants of the murine BW5147 lymphoma cell-line, we have previously identified 3 monoclonal antibodies (MAbs) that discriminate between metastatic and nonmetastatic BW5147-derived T-cell hybridomas and lymphomas, as well as BW5147-unrelated T-lymphomas. These MAbs were reported to recognize an identical membrane-associated sialoglycoprotein, termed "metastatic T-cell hybridoma antigen" (MTH-Ag). Here, we document that the expression pattern of the MTH-Ag on metastatic and nonmetastatic BW5147 variants correlates with that of the P-selectin glycoprotein ligand 1 (PSGL-1), a sialomucin involved in leukocyte recruitment to sites of inflammation. Moreover, the MAbs against the MTH-Ag recognize PSGL-1 when it is transfected in MTH-Ag-negative BW5147 variants, suggesting that the MTH-Ag is PSGL-1. Overexpression of MTH-Ag/PSGL-1 in MTH-Ag-negative BW5147 variants did not affect their in vivo malignancy. Yet, down-regulation of MTH-Ag/PSGL-1 expression on metastatic, MTH-Ag-positive BW5147 variants, using an RNA interference (RNAi) approach, resulted, in a dose-dependent manner, in a significant reduction of liver and spleen colonization and a delay in mortality of the recipient mice upon intravenous inoculation. Collectively, these results demonstrate that, although MTH-Ag/PSGL-1 overexpression alone may not be sufficient for successful dissemination and organ colonization, MTH-Ag/PSGL-1 plays a critical role in hematogenous metastasis of lymphoid cancer cells.

Multimodality imaging of T-cell hybridoma trafficking in collagen-induced arthritic mice: image-based estimation of the number of cells accumulating in mouse paws

Appropriate targeting of therapeutic cells is essential in adoptive cellular gene therapy (ACGT). Imaging cell trafficking in animal models and patients will guide development of ACGT protocols. Collagen type II (C-II)-specific T cell hybridomas are transduced with a lentivirus carrying a triple fusion reporter gene (TFR) construct consisting of a fluorescent reporter gene (RG), a bioluminescent RG (hRluc), and a positron emission tomography (PET) RG. Collagen-induced arthritic (CIA) mice are scanned with a bioluminescence imaging camera before and after implantation of various known cell quantities in their paws. Linear regression analysis yields equations relating two parameters of image signal intensity in mice paws to the quantity of hRluc expressing cells in the paws. Afterward, trafficking of intravenously injected cells is studied by quantitative analysis of bioluminescence images. Comparison of the average cell numbers does not demonstrate consistently higher accumulation of T-cell hybridomas in the paws with higher inflammation scores, and injecting more cells does not cause increased accumulation. MicroPET images illustrate above background signal in the inflamed paws and chest areas of CIA mice. The procedures described in this study can be used to derive equations for cells expressing other bioluminescent RGs and in other animal models.

Presentation of arthritogenic peptide to antigen-specific T cells by fibroblast-like synoviocytes

OBJECTIVE

To assess the ability of rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) to function as antigen-presenting cells (APCs) for arthritogenic autoantigens found within inflamed joint tissues.

METHODS

Human class II major histocompatibility complex (MHC)-typed FLS were used as APCs for murine class II MHC-restricted CD4 T cell hybridomas. Interferon-gamma (IFNgamma)-treated, antigen-loaded FLS were cocultured with T cell hybridomas specific for immunodominant portions of human cartilage gp-39 (HC gp-39) or human type II collagen (CII). T cell hybridoma activation was measured by enzyme-linked immunosorbent assay of culture supernatants for interleukin-2. Both synthetic peptide and synovial fluid (SF) were used as sources of antigen. APC function in cocultures was inhibited by using blocking antibodies to human class II MHC, CD54, or CD58, or to murine CD4, CD11a, or CD2.

RESULTS

Human FLS could present peptides from the autoantigens HC gp-39 and human CII to antigen-specific MHC-restricted T cell hybridomas. This response required pretreatment of FLS with IFNgamma, showed MHC restriction, and was dependent on human class II MHC and murine CD4 for effective antigen presentation. Furthermore, FLS were able to extract and present antigens found within human SF to both the HC gp-39 and human CII T cell hybridomas in an IFNgamma-dependent and MHC-restricted manner.

CONCLUSION

RA FLS can function as APCs and are able to present peptides derived from autoantigens found within joint tissues to activated T cells in vitro. In the context of inflamed synovial tissues, FLS may be an important and hitherto overlooked subset of APCs that could contribute to autoreactive immune responses.

Targeting Ligand-Induced Binding Sites on GPIIb/IIIa via Single-Chain Antibody Allows Effective Anticoagulation Without Bleeding Time Prolongation

Objective— Therapeutic anticoagulation is widely used, but limitations in efficacy and bleeding complications cause an ongoing search for new agents. However, with new agents developed it seems to be an inherent problem that increased efficiency is accompanied by an increase in bleeding complications. We investigate whether targeting of anticoagulants to activated platelets provides a means to overcome this association of potency and bleeding.

Methods and Results— Ligand-induced binding sites (LIBS) on fibrinogen/fibrin-binding GPIIb/IIIa represent an abundant clot-specific target. We cloned an anti-LIBS single-chain antibody (scFv anti-LIBS ) and genetically fused it with a potent, direct factor Xa (fXa) inhibitor, tick anticoagulant peptide (TAP). Specific antibody binding of fusion molecule scFv anti-LIBS -TAP was proven in flow cytometry; anti-fXa activity was demonstrated in chromogenic assays. In vivo anticoagulative efficiency was determined by Doppler-flow in a ferric chloride–induced carotid artery thrombosis model in mice. ScFv anti-LIBS -TAP prolonged occlusion time comparable to enoxaparine, recombinant TAP, and nontargeted mutant-scFv-TAP. ScFv anti-LIBS -TAP revealed antithrombotic effects at low doses at which the nontargeted mutant-scFv-TAP failed. In contrast to the other anticoagulants tested, bleeding times were not prolonged by scFv anti-LIBS -TAP.

Conclusions— The novel clot-targeting approach of anticoagulants via single-chain antibody directed against a LIBS-epitope on GPIIb/IIIa promises effective anticoagulation with reduced bleeding risk.

IgE basement membrane zone antibodies induce eosinophil infiltration and histological blisters in engrafted human skin on SCID mice

Bullous pemphigoid (BP) is characterized by the deposition of IgG in the basement membrane zone, infiltration of eosinophils, and blister formation. The purpose of this study was to evaluate a potential role of IgE basement membrane antibodies in the histological findings of BP. LABD97 is a component of the shed ectodomain of bullous pemphigoid antigen 2. We have developed an IgE hybridoma to LABD97 antigen. This hybridoma was injected subcutaneously in SCID mice with engrafted human skin. A subcutaneous hybridoma secreting IgE antibodies developed. An IgE mouse hybridoma to trinitrophenyl was used as a control. Human grafts and mouse skin were examined grossly over 21 days, histologically, and immunopathologically at day 21 after injection of the hybridoma. A visible subcutaneous tumor developed in 10-14 days. Erythema and intense scratching developed 2-3 days before the tumor in test mice, but not in controls. At day 21, 16/16 test mice developed intense eosinophil infiltration and degranulation of the human mast cells within the grafts and 13/16 developed histological, but not clinically visible, basement membrane blisters. Human skin grafts of control mice and normal mouse skin on the test mice and control mice did not develop any histological abnormalities. IgE antibodies to LABD97 recapitulate the histological inflammatory process seen in BP.

Modification of Cepsilon mRNA expression by EBV-encoded latent membrane protein 1

To evaluate the effect of expression of latent membrane protein (LMP) 1 encoded by Epstein-Barr virus (EBV) on Cɛ mRNA expression, mRNA levels were examined by RT-PCR or Northern blot analysis upon transient transfection of LMP1 in the splenocytes derived from Brown-Norway rats with or without immunization with 2,4-dinitrophenyl-conjugated Ascaris suum antigen. Splenocytes were transfected with LMP1 expression vector, pSG5-LMP1, using lipofection method. Cɛ mRNA levels were considerably increased by transfection with pSG5-LMP1 in the splenocytes derived from the nonimmunized rats; however, Cɛ mRNA levels were decreased in the splenocytes derived from the immunized rats. Cɛ mRNA expression in IgE-producing cells are modulated by LMP1, which might depend on the differentiation status of B cells upon exposure to allergen.

Viewing malignant melanoma cells as macrophage-tumor hybrids

Cutaneous malignant melanoma (CMM) begins in the epidermis as the clonal emergence of melanocytes having a deregulated mitotic cycle. In a manner not yet understood, some descendents of these cells loosen their adhesions in situ and migrate into the dermis, thus initiating the processes of invasion and metastasis. These cells look and act much like macrophage-melanoma hybrids created in the lab or arising in mice. But genetic proof for hybrids in human melanoma is still lacking. Nonetheless, should tumor cell hybridization account for the invasive phenotype, this would surely evoke new therapeutic approaches regarding mechanisms of cell fusion and hybrid-specific molecular signatures. Here are described some of the remarkable phenotypic similarities between experimental macrophage-melanoma hybrids and CMM. The results suggest that invasive and metastatic CMM might well arise through fusion and genomic hybridization between melanoma cells and migratory bone marrow-derived cells.

Pyridone 6, A Pan-Janus–Activated Kinase Inhibitor, Induces Growth Inhibition of Multiple Myeloma Cells

Interleukin-6 (IL-6) and the subsequent Janus-activated kinase (JAK)-dependent signaling pathways play a critical role in the pathogenesis of multiple myeloma. Here, we compared the sensitivity and specificity of a novel pan-JAK inhibitor, tetracyclic pyridone 6 (P6), with that of AG490 in a panel of myeloma-derived cell lines. P6 induced growth arrest and subsequent apoptosis of the IL-6-dependent hybridoma and myeloma-derived cell lines (B9 and INA-6) grown either in IL-6-containing medium or in the presence of bone marrow-derived stromal cells (BMSC) using much lower concentrations of drug and with significantly faster kinetics than AG490. Myeloma-derived cell lines, which either express constitutively activated JAK/signal transducers and activators of transcription (STAT) 3 (U266) or are IL-6 growth stimulated (KMS11), are partially growth inhibited by P6. However, P6 does not inhibit the growth of myeloma-derived cell lines lacking activated JAKs/STATs nor does it inhibit mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase activity compared with AG490, which led to activation of ERK and induced robust apoptosis of all the examined cell lines. Finally, P6 inhibited the growth of primary myeloma patient samples grown in the presence of BMSCs. Thus, P6 is a more sensitive and specific inhibitor of JAK-STAT3 activity compared with AG490 and potently inhibited the growth of primary myeloma cells and myeloma-derived cell lines grown on BMSCs.

Radioimmunotherapy of CD22-expressing Daudi tumors in nude mice with a 90Y-labeled anti-CD22 monoclonal antibody

A study was undertaken to investigate the efficacy of a high affinity, rapidly internalizing anti-CD22 monoclonal antibody for selectively delivering high-energy (90)Y radioactivity to B lymphoma cells in vivo. The antibody, RFB4, was readily labeled with (90)Y using the highly stable chelate, 1B4M-diethylenetriaminepentaacetic acid. Labeled RFB4 selectively bound to the CD22(+) Burkitt's lymphoma cell line Daudi, but not to CD22(-) control cells in vitro as compared with a control antibody, and was more significantly bound (P = 0.03) to Daudi solid tumors growing in athymic nude mice. Biodistribution data correlated well with the antitumor effect. The therapeutic effect of (90)Y-labeled anti-CD22 (Y22) was dose-dependent, irreversible, and the best results were achieved in mice receiving a single i.p. dose of 196 microCi. These mice displayed a significantly better (P < 0.01) antitumor response than control mice and survived >200 days with no evidence of tumor. Histology studies showed no significant injury to kidney, liver, or small intestine. Importantly, tumor-bearing mice treated with Y22 had no radiologic bone marrow damage compared with tumor-bearing mice treated with the control-labeled antibody arguing that the presence of CD22(+) tumor protected mice from bone marrow damage. When anti-CD22 radioimmunotherapy was compared to radioimmunotherapy with anti-CD19 and anti-CD45 antibodies, all three antibodies distributed significantly high levels of radioisotope to flank tumors in vivo compared with controls (P < 0.05), induced complete remission, and produced long-term, tumor-free survivors. These findings indicate that anti-CD22 radioimmunotherapy with Y22 is highly effective in vivo against CD22-expressing malignancies and may be a useful therapy for drug-refractory B cell leukemia patients.

Neoplastic transformation of a human hybrid cell line by alpha particles in relation to mammography X rays

The hybrid cell line CGL1 is the only cell line which allows quantitation of neoplastic transformation in human cells. Hybrid cells were exposed to 3.4 MeV alpha particles or to mammography X rays (29 kV(p)) and both survival and neoplastic cell transformation were assayed. For comparison, previously published data obtained with 200 kV(p) X rays are also included. Alpha particles were significantly more efficient than 29 kV(p) X rays in cell killing. Surprisingly, the efficiency of mammography X rays for the induction of neoplastic cell transformation was close to that observed for alpha particles.

[Expression of midkine fusion protein and preparation and application of its monoclonal antibodies]

AIM

To express midkine (MK) protein, prepare its monoclonal antibody (mAb), and detect its expression in tumor cells.

METHODS

The human MK gene fragment was cloned from kidney cancer tissues by RT-PCR and inserted into the prokaryotic expression vector pMS-31b. The MS2-MK fusion protein was expressed in E.coli after temperature induction. The purified fusion protein was used to immunize BALB/c mice to prepare mAbs against MK by routine hybridoma technique. The Ig subclasses of the mAbs were identified by ELISA. The expression of MK in tumor cells was detected with the mAbs.

RESULTS

MK gene was cloned and MS2-MK fusion protein was expressed successfully. Two hybridoma cell lines secreting anti-MK mAbs were obtained. The Ig subclass of the 2 mAbs was IgG1 and IgG2a, respectively. MK was expressed in gastric carcinoma cell line MGC803 and gastric cancer tissue.

CONCLUSION

The MS2-MK fusion protein was expressed in E.coli and the mAbs against MK were pepared, which allow futher research on MK function.

Estimating the Growth Kinetics of Experimental Tumors From as Few as Two Determinations of Tumor Size: Implications for Clinical Oncology

Clinical information on tumor growth is often limited to a few determinations of the size of the tumor burden taken at variable time. As a consequence, fitting of growth equations to clinical data is hampered by the small number of available data. On the other hand, characterising the tumor growth kinetics in terms of clinically relevant parameters, such as the doubling time of the tumors, is increasingly required to optimize and personalise treatments. A computational method is presented which can estimate the growth kinetics of tumors from as few as two determinations of its size taken at two successive time points, provided the size at which tumor growth saturates is known. The method is studied by using experimental data obtained in vitro with multicell tumor spheroids and in vivo with tumors grown in mice, and its outputs are compared to those obtained by fitting of experimental data with the Gompertz growth equation. Under certain assumptions and limitations the method provides comparable estimates of the doubling time of tumors with respect to the classical nonlinear fitting approach. The method is then tested against simulated tumor growth trajectories spanning the range of tumor sizes observed in the clinics. The simulations show that a relative classification of tumors on the basis of their growth kinetics can be obtained even if the size at which tumor growth saturates is not known. This result opens the possibility to classify patients bearing fast or slow growing tumors and, hence, to adapt therapeutic regimens under a more rationale basis.

Inhibition of tumor angiogenesis in vivo by a monoclonal antibody targeted to domain 5 of high molecular weight kininogen

We have shown that human high molecular weight kininogen is proangiogenic due to release of bradykinin. We now determined the ability of a murine monoclonal antibody to the light chain of high molecular weight kininogen, C11C1, to inhibit tumor growth compared to isotype-matched murine IgG. Monoclonal antibody C11C1 efficiently blocks binding of high molecular weight kininogen to endothelial cells in a concentration-dependent manner. The antibody significantly inhibited growth of human colon carcinoma cells in a nude mouse xenograft assay and was accompanied by a significant reduction in the mean microvascular density compared to the IgG control group. We also showed that a hybridoma producing monoclonal antibody C11C1 injected intramuscularly exhibited markedly smaller tumor mass in a syngeneic host compared to a hybridoma producing a monoclonal antibody to the high molecular weight kininogen heavy chain or to an unrelated plasma protein. In addition, tumor inhibition by purified monoclonal antibody C11C1 was not due to direct antitumor effect because there was no decrease of tumor cell growth in vitro in contrast to the in vivo inhibition. Our results indicate that monoclonal antibody C11C1 inhibits angiogenesis and human tumor cell growth in vivo and has therapeutic potential for treatment of human cancer. (Blood. 2004;104:2065-2072)

In vivo cellular imaging of magnetically labeled hybridomas in the spleen with a 1.5-T clinical MRI system

The feasibility of in vivo cellular imaging using a 1.5 T clinical magnet was studied in the mouse. Hybridoma cells were labeled with anionic gamma-Fe2O3 superparamagnetic iron oxide nanoparticles. These were internalized by the endocytose pathway. Both electron spin resonance and magnetophoresis as a measure of the labeled cells migration velocity under a magnetic field were used to quantify particle uptake. A fast (< 2 hr) and substantial (up to 5 pg of iron per cell) internalization of nanoparticles by hybridomas was found, with good agreement between the two methods used. Hybridomas labeled with 2.5 pg iron per cell were injected intraperitoneally to male Swiss nude mice. A decrease in the spleen signal, suggesting a "homing" of labeled hybridomas to this organ, was found 24 hr later by MRI performed at 1.5 T. Furthermore, in labeled cells recovered from the spleen by ex vivo magnetic sorting, a mean of 0.5 pg iron per cell was found, i.e., a value five times lower than that of the injected hybridomas. This finding is consistent with in vivo proliferation of these cells. In addition, the amount of labeled hybridomas present in the spleen was found to correlate with MRI signal intensity.

SING: a novel strategy for identifying tumor-specific, CTL-recognized tumor antigens

Traditional methods for identifying T cell-recognized tumor antigens (Ags) are laborious and time-consuming. In an attempt to simplify the procedure, a novel strategy, SING (SIgnal transduction molecule-mediated, NFAT-controlled, GFP expression) was established as a direct approach for cloning T cell-recognized tumor Ags. In the SING system, a mouse T cell line (BW5147) was transduced with a chimeric H-2Kb construct containing T cell-signaling domains and a green fluorescent protein (GFP) reporter gene under the transcriptional control of nuclear factor of activated T cells (NFAT). The resultant BW5147 cells were named BS cells. This cell line could "sense" TCR stimulation through the T cell-signaling domains after coculture with Ag-specific T cells and then become fluorescent (expressing green fluorescence protein, GFP+) in the presence of Ag peptides. The interaction between BS cells and Ag-specific T cells could be enhanced by addition of costimulatory signals. Currently, BS cells have been optimized to "sense" TCR stimulation after being pulsed with the relevant peptides at concentrations as low as 10(-9) M. Endogenous Ag-expressing BS cells could also become fluorescent after coculture with Ag-specific T cells. Our results provide a proof of principle for using the SING system to directly isolate Ag-expressing BS cells from BS cell repertoires, which are retrovirally transduced with tumor-derived cDNA libraries. Once tumor Ag-marked BS cells are identified, the sequences encoding tumor Ags could be easily retrieved by PCR amplification of the genomic DNA using vector-specific primers.

The Cognition-Enhancer Nefiracetam Inhibits Both Necrosis and Apoptosis in Retinal Ischemic Models in Vitro and in Vivo

The retinal ischemic-reperfusion stress (130 mm Hg, 45 min) caused neuronal damage throughout all cell layers and reduced the thickness of retinal layer by 30% at 7 days after the stress of mouse retina. The intravitreous injection of 100 pmol of nefiracetam, a cognition-enhancer, completely prevented the damage when it was given 30 min before and 3 h after the stress. Partial prevention was observed when it was given 24 h after the stress, or low dose (10 pmol) nefiracetam was given 30 min before the stress. However, aniracetam had no effect. In the retinal cell line N18-RE-105, the ischemic-reperfusion stress by 2 h culture under the serum-free condition with low oxygen (less of 0.4% O(2)) and low glucose (1 mM) caused necrosis or apoptosis in the low-density (0.5 x 10(4) cell/cm(2))or high-density (5 x 10(4) cell/cm(2)) culture, respectively. The necrosis showed membrane disruption, loss of electron density, and mitochondrial swelling, whereas apoptosis showed nuclear fragmentation and condensation in transmission electron microscopical analyses and in experiments using specific cell death markers. Nefiracetam inhibited both necrosis and apoptosis, whereas brain-derived neurotrophic factor (BDNF) inhibited only apoptosis. The cell-protective actions of nefiracetam were abolished by nifedipine and omega-conotoxin GVIA, L-type and N-type calcium channel blocker, but not by PD98059 or wortmannin, extracellular signal-regulated kinase 1/2 or phosphoinositide 3-kinase inhibitor, respectively, whereas those of BDNF were abolished by PD98059 and wortmannin, but not by nifedipine and omega-conotoxin GVIA. All these findings suggest that nefiracetam inhibit necrosis and apoptosis occurred in the ischemic/hypoxic neuronal injury through an increase in Ca(2+) influx.

[Modification of the antiapoptotic ability of H18 hybridoma cells]

To construct eukaryotic expression vector containing murine bcl-XL and stably express it in H18 hybridoma cells in order to enhance hybridoma cells antiapoptotic ability. PCR was used to obtain 710bp murine bcl-XL cDNA from pGEM-T-bcl-XL. Then the recombinant expression vector pEF-bcl-XL was constructed by cloning bcl-XL cDNA into eukaryotic expression vector pEF by Pst I and Xho I double digestion. After transfection into H18 hybridoma cells through lipofectamine 2000, the stable expression cell line was screened by 800mg/L G418. The expression of bcl-XL gene was detected by Western blotting. Flow cytometer was used to test the modified hybridoma cells ability to resist apoptosis induced by 0.4mmol/L Sodium Butyrate. The eukaryotic expression vector pEF-bcl-XL was successfully constructed and stably expressed in H18 hybridoma cells. Our data showed that stably transfected H18 cells expressed high levels of Bcl-XL. Under the condition of 0.4mmol/L NaBu, the production of antibody was to be significantly increased by more than 3-fold in stably transfected H18, which resulted from suppressing the NaBu-induced apoptosis and allowing stably transfected H18 cells to grow at higher viability and extend culture longevity by > 3 days. The increased culture longevity by inhibition of NaBu-induced apoptosis by inducible expression of Bcl-XL combined with the enhanced secretion of antibody by NaBu contributed to the enhancement of final antibody concentration in the stably transfected H18 cells culture. The final antibody concentration of stably transfected H18 cells in the presence of NaBu was three-fold higher than that of H18 cells culture in the absence of NaBu. Together, our results showed that butyrate is of practical interest for production of antibody. NaBu-induced apoptosis of hybridoma cells could be inhibited by inducible expression of Bcl-XL. The expression of murine bcl-XL gene in hyridoma cells and the increasing antiapoptosis ability of hybridoma cells are of significance in further use of hybridoma cells in high density large scale cell culture.

Suppression of experimental lupus nephritis by aberrant expression of the soluble E-selectin gene

Circulating leukocytes, particularly neutrophils and monocytes, are important effector cells in the induction of many forms of glomerulonephritis. Adhesion molecules, especially selectins, are also thought to be critical for the development of this disease. We examined the possible suppressive effect of soluble E-selectin on the development of experimental lupus nephritis induced by the injection of a hybridoma clone (2B11.3) derived from an MRL/MpJ-lpr/lpr lupus mouse. This clone produces IgG3 antibodies that induce severe proliferative glomerulonephritis resembling lupus nephritis when injected into normal mice. Transgenic mice with a soluble E-selectin gene were injected intraperitoneally with the hybridoma cells and histopathologically examined on day 15. As a result, the development of glomerulonephritis was significantly suppressed. This suppression was characterized by fewer inflammatory cell infiltrates, compared with non-transgenic litter mates, despite the fact that there were no remarkable differences in immunoglobulin deposits or expression of E-selectin between the two groups. These findings suggest that by controlling inflammatory cell infiltration, soluble E-selectin plays a preventative role in the development of a particular type of lupus nephritis.

Human monoclonal rheumatoid synovial B lymphocyte hybridoma with a new disease-related specificity for cartilage oligomeric matrix protein

Joint-specific self-Ags are considered to play an important role in the induction of synovial T and B cell expansion in human rheumatoid arthritis (RA). However, the nature of these autoantigens is still enigmatic. In this study a somatically mutated IgG2 lambda B cell hybridoma was established from the synovial membrane of an RA patient and analyzed for its Ag specificity. A heptameric peptide of cartilage oligomeric matrix protein (COMP) could be characterized as the target structure recognized by the human synovial B cell hybridoma. The clonotypic V(H) sequences of the COMP-specific hybridoma could also be detected in synovectomy material derived from five different RA patients but in none of the investigated osteoarthritis cases (n = 5), indicating a preferential usage of V(H) genes closely related to those coding for a COMP-specific Ag receptor in RA synovial B cells. Moreover, the COMP heptamer was preferentially recognized by circulating IgG in RA (n = 22) compared with osteoarthritis patients (n = 24) or age-matched healthy controls (n = 20; both p < 0.0001). Hence, the COMP-specific serum IgG is likely to reflect local immune responses toward a cartilage- and tendon-restricted Ag that might be crucial to the induction of tissue damage in RA.

Soluble MHC class I molecules induce cellular death in a CD8+ T-cell hybridoma tumor model

T cells undergo activation-induced cell death (AICD) after T-cell receptor cross-linking in the absence of co-stimulation. In this study, we examined whether AICD induced by purified MHC class I molecules could be used to selectively eliminate tumor cells in T-cell malignancies. As a model, soluble H-2K(b) molecules refolded with the chicken ovalbumin SIINFEKL peptide (K(b)-OVA) and a CD8+ T-cell hybridoma (CD8-OVA) specific for this peptide were used. Addition of CD8-OVA hybridoma cells to plastic plates adsorbed with K(b)-OVA molecules resulted in a concentration-dependent decrease in cellular proliferation. Exogenous IL-4 further depressed the proliferation of CD8-OVA cells in a dose-dependent manner in the presence, but not in the absence, of K(b)-OVA. Staining of these cells with propidium iodide confirmed that the decrease in cellular proliferation was due to apoptosis. The cytotoxic effect of plastic-immobilized K(b)-OVA could be mimicked by soluble K(b)-OVA tetramers. Furthermore, co-injection of K(b)-OVA tetramers and CD8-OVA cells into mice suppressed the tumorigenicity of CD8-OVA cells. In conclusion, we describe a system whereby soluble MHC class I molecules can be used to selectively induce cellular death in a monoclonal T-cell tumor model. With future development, the use of MHC molecules may help to eliminate specific T cells in cases of T-cell malignancy and auto-immunity.

Antiallergic effect of apple polyphenols on the allergic model mouse

We studied here the antiallergic effect of apple condensed tannins (ACT) administered orally to a type I allergy model mouse transplanted with an IgEL a2 hybridoma secreting anti-2,4,6-trinitrophenyl (TNP) immunoglobulin E (IgE). The oral administration of ACT significantly inhibited the ear swelling responses at 1 h after antigen-stimulation with picryl chloride. The response was dose dependent within 0.1 to 10 mg/mouse. The inhibition of the ear swelling response reached the maximal level (90% inhibition) when ACT was administered 2 h before the antigen challenge. These findings suggest that ACT has an antiallergic effect on type I allergic symptoms.

N-acetylcysteine increases apoptosis induced by H(2)O(2) and mo-antiFas triggering in a 3DO hybridoma cell line

N-Acetylcysteine (NAC) has been used as an antioxidant to prevent apoptosis triggered by different stimuli in different cell types. It is common opinion that cellular redox, which is largely determined by the ratio of oxidized and reduced glutathione (GSH), plays a significant role in the propensity of cells to undergo apoptosis. However, there are also contrasting opinions stating that intracellular GSH depletion or supplemented GSH alone are not sufficient to lead cells to apoptosis or conversely protect them. Unexpectedly, this study shows that NAC, even if it maintains the peculiar characteristics of an agent capable of reducing cell proliferation and increasing intracellular GSH content, increases apoptosis induced by H(2)O(2) treatment and mo-antiFas triggering in a 3DO cell line. We found that 24 h of NAC pre-treatment can shift cellular death from necrotic to apoptotic and determine an early expression of FasL in a 3DO cell line treated with H(2)O(2).

A metalloproteinase inhibitor prevents acute graft-versus-host disease while preserving the graft-versus-leukaemia effect of allogeneic bone marrow transplantation

Tumor necrosis factor (TNF) and Fas ligand (FasL) have been implicated in the pathogenesis of graft-versus-host disease (GVHD). Several recent studies have shown that some metalloproteinase mediates TNF-alpha and FasL processing. We examined the ameliorating effect of a hydroxamic acid-based metalloproteinase inhibitor (KB-R7785) that inhibits TNF-alpha and FasL release in a lethal acuteGVHD model in mice. The ameliorating effect of KB-R7785 was superior to that of anti-TNF-alpha antibody. We also examined the effect of KB-R7785, which we previously demonstrated a potent ameliorating effect on acute GVHD, on graft-versus-leukemia (GVL) effect of allogeneic bone marrow transplantation (BMT). Administration of KB-R7785 without bone marrow cells and spleen cells (BMS). significantly prolonged the survival of IgE-producing B53 hybridoma cell-inoculated (C57BL/6 x BALB/c) F1 (CBF1) mice by inhibiting the infiltration of B53 cells into the liver and spleen. Transplantation of B6 BMS without KB-R7785 resulted in the death of most recipients due to acute GVHD while efficiently eliminating B53 cells. Administration of KB-R7785 along with B6 BMS resulted in 50% survival of B53-inoculated CBF1 mice over 50 days without histological manifestations of acute GVHD or residual B53 cells. These results suggest that KB-R7785 could be a potent therapeutic agent for GVHD, and indicate the beneficial effects of KB-R7785 that inhibit tumor infiltration and prevent acute GVHD while preserving the GVL effect of allogeneic BMT.

Evidence for a p23 caspase-cleaved form of p27[KIP1] involved in G1 growth arrest

p27[KIP1] (p27) is a cyclin dependent kinase inhibitor, involved in the negative regulation of G1 progression in response to a number of anti-proliferative signals. In this study we show, in growing mouse hybridoma (7TD1) and human myeloma (U266) cell lines, that p27 is highly expressed but slightly upregulated when cells are arrested, regardless to the phases of the cell cycle. In contrast, the specific blockade of these cells in early G1 phase reveals the induction of a protein of 23 kDa (p23) specifically recognized by polyclonal anti-p27 antibodies raised against the NH2 terminal part of p27 but not by anti-p21[CIP1] antibodies. Experiments using caspase inhibitors strongly suggest that p23 results from the proteolysis of p27 by a 'caspase-3-like' protease. This cleavage leads to the cytosolic sequestration of p23 but does not alter its binding properties to CDK2 and CDK4 kinases. Indeed, p23 associated in vivo with high molecular weight complexes and coprecipitated with CDK2 and CDK4. We demonstrate by transfection experiments in SaOS-2 cells that p23 induces a G1 phase growth arrest by inhibition of cyclin/CDK2 activity. In summary we describe here a caspase-cleaved form of p27, induced in absence of detectable apoptosis and likely involved in cell cycle regulation.

Transcriptional control of the IL-5 gene by human helper T cells: IL-5 synthesis is regulated independently from IL-2 or IL-4 synthesis

BACKGROUND

IL-5 is fundamentally involved in eosinophilic inflammation. Control of IL-5 production may be effective for the management of allergic diseases.

OBJECTIVE

We aimed to find the transcriptional mechanisms that regulate the IL-5 gene to selectively control IL-5 synthesis.

METHODS

Allergen-specific T-cell clones and T-cell hybridomas were established from the peripheral blood lymphocytes of patients with asthma, and the transcriptional regulation of the IL-5 gene was investigated with transient transfection and electrophoretic mobility shift analysis.

RESULTS

A human IL-5 promoter/enhancer-luciferase gene construct, pIL-5(-511)Luc, was transcribed on activation of IL-5-producing T-cell clones, but not IL-5-nonproducing clones. pIL-5(-511)Luc was transcribed by T-cell hybridomas derived from fusion between IL-5-producing T-cell clones and an IL-5 gene-nonexpressing T-cell line, but not by hybridomas derived from IL-5-nonproducing T-cell clones. IL-5 synthesis was not only induced by T-cell receptor stimulation but also by IL-2 receptor stimulation. Binding of NF-AT, NF-kappaB, and AP-1 was induced by T-cell receptor (TcR) stimulation, although there was no significant upregulation of binding by IL-2 stimulation.

CONCLUSION

IL-5 synthesis by human helper T cells is regulated at the transcriptional level. A unique transcriptional mechanism distinct from those regulating the IL-2 or IL-4 genes seems to control the IL-5 gene. Selective regulation of IL-5 gene transcription may be useful for treating eosinophlic inflammation.

Isolation of a low-molecular-weight growth inhibitory factor from hybridoma cell cultures

A low-molecular-weight growth inhibitory factor was produced by hybridoma cells. The number of viable cells in hybridoma cell cultures reached a maximum of about 5 x 10(5) cells/ml when the inhibitory factor had accumulated to a critical level, after which the number of viable cells declined with a concomitant increase in the number of dead cells. The growth inhibitory factor was purified to apparent homogeneity by ultrafiltration, reverse-phase chromatography, passage through cation exchangers, and gel filtration. Analysis by reverse-phase chromatography and micellar electrokinetic chromatography using a capillary electrophoresis system indicated that the final inhibitory fraction was pure. The factor had a molecular weight of 500 or less, as judged by ultrafiltration, and its behavior upon ion-exchange chromatography indicated that it was uncharged. Its absorbance maximum at 263 nm indicated that it was not a peptide, but that it may have a conjugated system of carbon-carbon double bonds.

Comparison of four strategies for tumour vaccination in the B16-F10 melanoma model

We have compared four cell-based tumour vaccine strategies in prevention experiments using the B16-F10 melanoma model. Two of these are thought to favour the direct antigen presentation pathway (B16-F10 expressing B7.1 and hybrids made between B16-F10 cells and macrophages) and the other two strategies are thought to act by an indirect pathway of presentation (allogeneic tumour cells and autologous tumour cells combined with a powerful adjuvant (Provax-IDEC Pharmaceuticals)). Only the two latter vaccines promoted antitumour activity, whereas the vaccines consisting of B7.1-expressing tumour cells or the hybrid vaccine failed to provide any antitumour activity. Recently human trials have commenced using transfection of the B7.1 molecule, as well as employing the hybrid technology to make tumour-B cell hybrids or tumour and dendritic cell hybrids. Our results suggest that these approaches could be disappointing in the clinics if not optimised.

Use of a semi-automated, robotic radioimmunoassay to measure cAMP generated by activation of DP-, EP2-, and IP-prostaglandin receptors in human ocular and other cell types

The aim of these studies was to compare the effects of several prostaglandin agonists on adenylyl cyclase activity in embryonic bovine tracheal (EBTr) cells, transformed human nonpigmented ciliary epithelial (NPE) cells and National Cancer Bank (NCB-20) cells. These cell types have been shown to express DP, EP2 and IP prostaglandin (PG) receptors, respectively. Cyclic AMP (cAMP) generation was measured by manual and semi-automated radioimmunoassay (RIA) techniques. ZK118182 (EC50 = 10-27 nM), PGE2 (EC50 = 21-27 nM) and PGI2 (EC50 = 3.5-4 nM) had the highest potency at the DP, EP2 and IP receptors, respectively. A plot of potency (EC50) values generated with both techniques showed a high degree of correlation for all three receptors. These studies provide further characterization of prostanoid receptor functional responses in three cell types and demonstrate the advantages of a semi-automated RIA method for the analysis of the second messenger cAMP.

Method for production of neuronal hybridoma using emetine and actinomycin D

Neuronal hybrid cells established by somatic cell fusion are useful for studies of neuronal properties at the molecular level (Hammond, D.N., Lee, H.J., Tonsgard, J.H. and Wainer, B.H., Development and characterization of clonal cell lines derived from septal cholinergic neurons, Brain Res., 512 (1990) 190-200; Wainwright, M.S., Perry, B.D., Won, L.A., O'Malley, K.L., Wang, W.Y., Ehrlich, M.E. and Heller, A., Immortalized murine strial neuronal cell lines expressing dopamine receptors and cholinergic properties, J. Neurosci., 15 (1995) 676-688). The somatic cell fusion method requires a fusion partner which is unable to survive in the selection medium if it does not fuse with primary cells to isolate the hybrid cells. Hypoxanthine guanine phosphoribosyltransferase (HPRT)-deficient partner cells and hypoxanthine, aminopterin and thymidine (HAT) selection medium are commonly used for this procedure (Harlow, E. and Lane, D. (Eds.), Antibodies: a Laboratory Manual, Cold Spring Harbor Laboratory Publications, New York, 1988, pp. 139-243). The present method requires neither HPRT-deficient cells nor HAT medium. Primary neurons are fused with the C1300 neuroblastoma cells pretreated with emetine (Grollman, A.P., Inhibitors of protein biosynthesis, J. Biol. Chem., 243 (1968) 4089-4094), an inhibitor of ribosomes and actinomycin D (Perry, R.P., Selective effects of actinomycin D on the intracellular distribution of RNA synthesis in tissue culture cells, Exp. Cell Res., 29 (1963) 400-406), an inhibitor of ribosomal RNA (rRNA) synthesis, before fusion. By this treatment, we are able to isolate hybrid cells after fusion because non-fused C1300 cells die due to the loss of active ribosomes and protein synthesis, whereas C1300 cells fusing with primary cells survive due to the supply of intact ribosomes and rRNA from primary cells. This method produces neuronal hybrids at high efficiency.

The effect of space flight on monoclonal antibody synthesis in a hybridoma mouse cell line

The hybridoma cell line, 3G10G5, producing a monoclonal antibody to the major capsid protein VP1 from the avian polyomavirus budgerigar fledgling disease virus, was produced from a Balb/C mouse. This cell line was used to test the effects of microgravity on cellular processes, specifically protein synthesis. A time course study utilizing incorporation of [35S]methionine into newly synthesized monoclonal antibody was performed on STS-77. After 5.5 days, it was observed that cell counts for the samples exposed to microgravity were lower than those of ground-based samples. However, radiolabel incorporation of the synthesized monoclonal antibody was similar in both orbiter and ground control samples. Overall, microgravity does not seem to have an effect on this cell line's ability to synthesize IgG protein.

Immune bioactivity in shellfish toward serum-free cultured human cell lines

The biologically functional effect of eight kinds of hot-water extracts of shellfish on cultured human cell lines was examined in a serum-free medium model. Meretrix lusoria and Sinonovacula constricta extracts enhanced IgM secretion of both hybridoma HB4C5 and SI102 cells when cultured with the respective extracts. The purified principle exhibited remarked activity in the adsorbed fraction in hydroxyapatite and Concanavalin A columns. The extracts of Corbicula fluminea, Crassostreas gigas, Meretrix lusoria, Anadara granosa, and Sinonovacula constricta enhanced in nitroblue tetrazolium (NBT)-reducing ability of macrophage U-M cells. Meretrix lusoria, Anadara granosa, and Sinonovacula constricta were specifically cytotoxic to both cultures of MCF-7 breast cancer cells and HuH-6KK hepatoblastoma. These findings imply that the extracts of shellfish that were examined exhibited a differential effect on immune cells and tumor cells.

[Specific inhibitory effect of hybrid liposomes on the growth of hybridoma cells in vitro]

Remarkably high inhibitory effects of the hybrid liposomes composed of L-alpha-dimyristoyl-phosphatidylcholine (DMPC) and polyoxyethylenealkyl ether (C14(EO)n, n = 6-8 and C12(EO)n, n = 8-12)) on the growth of human lymphoma-human B-lymphocyte hybridoma (HF) cells in vitro were obtained. The hybrid liposomes composed of 90 mol% DMPC/10 mol% C14(EO)n (n = 6-8) or C12(EO)n (n = 8-12) were more fluid as compared with 90 mol% DMPC/10 mol% C14(EO)4 or C12(EO)n (n = 4, 23) hybrid liposomes on the basis of fluorescence polarization measurements. These results suggest that the inhibitory effects of the hybrid liposomes on the growth of HF cells should be related to the membrane fluidity. No toxicity to normal rats in vivo was observed in the experiment using 90 mol% DMPC/10 mol% C14(EO)7 or 90 mol% DMPC/10 mol% C12(EO)12 hybrid liposomes.

Expression of pertussis toxin adenosine diphosphate-ribosyltransferase in a T-cell hybridoma reduces metastatic capacity

T-cell hybridomas are highly metastatic, and their in vitro invasiveness correlates with metastatic capacity. Invasion is blocked by pertussis toxin (PT), which adenosine diphosphate (ADP)-ribosylates G1-proteins, and we have provided evidence that the PT-sensitive signal stimulates leukocyte function-associated antigen-1 (LFA-1)-mediated adhesion required for invasion. PT pretreatment of TAM2D2 T-cell hybridoma cells reduced metastasis, but only to a limited extent. In the present study, we have transfected the cDNA of the PT ADP-ribosyltransferase S1 subunit into TAM2D2 cells to abrogate G1-protein function permanently. We report here a substantial reduction in the metastatic capacity of two transfectants, S05 and S09, in which 88% and 95% of the G1-proteins was ADP-ribosylated. Two-thirds of the mice injected with S09 cells were tumor-free. Metastasis to the liver was almost completely prevented and less metastases were formed in the spleen and kidneys. Metastasis formation by S05 cells in liver and spleen was much reduced, but in lymph nodes and peritoneal tissues, metastases occurred with a frequency similar to that of controls. We conclude that G1-proteins play an important role in T-cell hybridoma metastasis. We propose that the reduction in metastasis is due to diminished entry of tumor cells from the blood into tissues.

Characterization of lpr-derived T cell hybridomas: Fas-deficient hybridomas are deathless, growth-arrested, and cytotoxic upon activation

T cell hybridomas that are deathless upon TCR crosslinking were generated from lpr mice. The deathless hybridomas (1.4 and 5D5) expressed extremely low Fas even after anti-CD3 activation, whereas activation-induced cell death (AICD) was observed for Fas-expressing hybridomas. The deathless hybridomas were activated to produce FasL and IL-2, indicating that the intrinsic defect in Fas expression or up-regulation resulted in AICD blockade. The deathless hybridoma cells expressed longer and stronger FasL cytotoxicity than AICD-sensitive hybridomas. Although deathless, activated 5D5 cells were arrested at the G1/S border. Growth arrest lasted for at least 5 days, but some cells eventually recovered and proliferated. The deathless 5D5 cells were used to demonstrate that AICD includes a fratricidal mechanism that kills AICD-sensitive bystanders. The deathless T cell hybridomas are useful tools for studying T cell activation-dependent functions sensitive to AICD.

Immortalized B-lymphocytes from rheumatoid synovial tissue show specificity for bacterial HSP 60

Several studies indicate a pathogenetic role of T-lymphocytes with specificity for heat shock proteins (HSP) in rheumatoid arthritis (RA). Surprisingly, there are no experimental data for B-lymphocytes with specificity for HSP. To investigate whether B-lymphocytes from rheumatoid synovial tissue show a specificity for HSP 60 we immortalized synovial tissue B-lymphocytes by the electrofusion technique and tested the specificity of the B-cell clones for HSP 60 by ELISA. Tissue samples from four patients with classic, active RA were used in this study. The isolated cells were electrofused in strongly hypo-osmolar medium with cells either of the mouse strain X63-Ag8-653 (Ag8) or the heteromyeloma strain HAB-1. Clones positive for IgG, the IgG fraction of the supernatant of the isolated synovial cells and the IgG of the serum of the patients were tested in an ELISA for reactivity to the recombinant HSP 60 or Yersinia enterocolitica, which shows great homology with mycobacterial HSP 65 and human HSP 60. The expression of this HSP 60 was studied in normal and rheumatoid synovial tissue using a polyclonal rabbit serum against HSP 60 from Y. enterocolitica (Ye HSP 60). In this way we investigate differences in the expression of HSP 60 and compared the pattern of this HSP60 with the pattern of mycobacterial HSP65 and human HSP 60 described by others. In three of four patients 10 IgG secreting B-cell clones showing a specificity for HSP 60 were detected. IgG specific for HSP 60 was also detected in the supernatant of the isolated synovial cells before fusion and in the serum of these patients. HSP 60 was demonstrated immunohistochemically within the rheumatoid synovial tissue and showed stronger expression with a different distribution when compared with the expression in normal synovial tissue. B-cell clones from rheumatoid synovial tissue thus exhibit a specificity for bacterial HSP 60, and a monospecific rabbit serum against this HSP shows strong reactivity within the rheumatoid synovial tissue. It may be postulated that a humoral HSP 60 response, initially directed against an infectious agent, could react with cross-reactive epitopes of rheumatoid synovial tissue or with self-HSP perpetuating the local inflammatory process.

Profile of energy metabolism in a murine hybridoma: glucose and glutamine utilization

The antibody-secreting murine hybridoma, CC9C10, was grown in batch culture in a medium containing 20 mM glucose and 2 mM glutamine. After 2 days of exponential growth, the glutamine content of the medium was completely depleted, whereas the glucose content was reduced to 60% of the original concentration. The glucose and glutamine metabolism was analyzed at midexponential phase by use of radioactively labelled substrates. Glycolysis accounted for the metabolism of most of the glucose utilized (> 96%) with flux through the pentose phosphate pathway (3.6%) and the TCA cycle (0.6%) accounting for the remainder. Glutamine was partially oxidised via glutaminolysis to alanine (55%), aspartate (3%), glutamate (4%), lactate (9%), and CO2 (22%). Calculation of the theoretical ATP production from these pathways indicated that glucose could provide 59% and glutamine 41% of the energy requirement of the cells.

LFA-1 integrin redistribution during T-cell hybridoma invasion of hepatocyte cultures and manganese-induced adhesion to ICAM-1

We have reported previously that the integrin LFA-1 is essential for metastasis of T-cell hybridomas to the liver. We show here that hepatocytes isolated from normal non-inflamed rat liver express intercellular adhesion molecule-1 (ICAM-1) at the dorsal surface and more prominently at the lateral and substratum-adherent surfaces. Anti-rat ICAM-1 mAb inhibited adhesion of TAM8C4 T-cell hybridoma cells to hepatocytes. Invasion between hepatocytes was not affected, but this is probably due to lack of penetration of the mAb between the hepatocytes. In all hepatocyte-adherent TAM8C4 cells, LFA-1 was concentrated at the adhesion site. Redistribution of ICAM-1 to the interacting hepatocyte membrane was also seen, but only for part of the adherent TAM8C4 cells. LFA-1 was highly concentrated on pseudopods of invading TAM8C4 cells inserted between hepatocytes, and on the upper surface of invaded TAM8C4 cells located under the hepatocytes. ICAM-1 was concentrated in the hepatocyte membrane overlying TAM8C4 cells located underneath the monolayer. These results suggests that ICAM-1 is of major importance for liver invasion by these lymphoma cells. For optimal adhesion to ICAM-1, LFA-1 on T-cell hybridomas requires activation, which apparently occurs upon contact with cell layers that are invaded (G. La Riviere et al., J. Cell Sci. 107, 551–559, 1994). LFA-1 can be activated artificially by Mn2+. To study LFA-1 redistribution upon ICAM-1 interaction with higher resolution, we performed immuno-EM on cells before and after Mn(2+)-induced adhesion and spreading on immobilized ICAM-1. By immune fluorescence, LFA-1 was observed to redistribute to the ICAM-1-adherent surface, and to be concentrated in lamellipodia of spreading TAM8C4 cells. By immuno-EM, LFA-1 was localized in microclusters of approximately 10 gold particles. This was seen in cells fixed in suspension, and the size of these clusters did not change upon adhesion to ICAM-1. LFA-1 was present at high density in thin filopodia, but again in microclusters of similar size. Comparable results were obtained with a cytotoxic T-cell clone. We conclude that Mn(2+)-induced activation of LFA-1 is not associated with the formation or enlargement of LFA-1 clusters.

Activated mouse astrocytes and T cells express similar CD44 variants. Role of CD44 in astrocyte/T cell binding

The CD44 adhesion molecule is expressed by astrocytes, glial-type cells which exhibit features of accessory cells for immune responses in the central nervous system. In primary cultures of mouse astrocytes, we have observed that surface expression and mRNA levels of CD44 are induced following stimulation with either PMA, or tumor necrosis factor alpha plus gamma interferon. Comparison of CD44 splice variants expressed by astrocytes and a T cell hybridoma shows that upon activation, both cell types express a similar pattern of CD44 transcripts. Thus, in both cell types, CD44 transcripts are produced which contain additional exons, including the exon v6 (known to be expressed by in vivo activated lymphocytes and by metastatic variants of tumor cells) as well as variants of larger size. In the autoimmune disease multiple sclerosis, activated T cells cross the blood-brain barrier and lead to inflammation in the central nervous system. Analysis of mice with experimental allergic encephalomyelitis, frequently used as an animal model of multiple sclerosis, shows that CD44 is induced in vivo on glial cells surrounding inflammatory lesions. Using an in vitro model for adhesion between T cells and astrocytes, we have found a correlation between the activation state of these cells and their adhesion potential. Dose-dependent inhibition of adhesion by hyaluronate and by anti-CD44 monoclonal antibody KM81 shows that CD44 is involved in the adhesive interactions between T cells and astrocytes.

A human monoclonal antibody, produced following in vitro immunization, recognizing an epitope shared by HLA-A2 subtypes and HLA-A28

In vitro immunization and subsequent immortalization of peripheral blood cells of a multiparous woman has resulted in the production of a stable human mouse heterohybridoma, 5C2A2, secreting an HLA-A2/A28-specific human monoclonal antibody. Although possibly exposed to HLA-A2 by transfusions, the cell donor showed no HLA-A2-specific serum antibodies. The present protocol for in vitro immunization includes the elimination of suppressor cells from the responder cell population, the presence of irradiated allogeneic lymphocytes as a source of antigen, as well as stimuli--recombinant interleukin-2 and a B-cell specific nucleoside analogue--causing the proliferation of B lymphocytes, prior to immortalization. The ability of the antibody 5C2A2 to detect all known HLA-A2 subtypes, except A2.3, and A28, allows identification of the serological epitope on the HLA-A2 molecule. Application of this in vitro immunization method allows the production of a set of HLA monoclonal antibody-secreting human hybridomas, independent of the existence of serum HLA antibodies in the lymphocyte donors.