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Podoplanin (PDPN), a small transmembrane mucin-like glycoprotein, is ectopically expressed on tumor cells. PDPN is known to be linked with several aspects of tumor malignancies in certain types of human and canine tumors. Therefore, it is considered to be a novel therapeutic target. Monoclonal antibodies targeting PDPN expressed in human tumor cells showed obvious anti-tumor effects in preclinical studies using mouse models. Previously, we generated a cancer-specific mouse-dog chimeric anti-PDPN antibody, P38Bf, which specifically recognizes PDPN expressed in canine tumor cells. In this study, we investigated the safety and anti-tumor effects of P38Bf in preclinical and clinical trials. P38Bf showed dose-dependent antibody-dependent cellular cytotoxicity against canine malignant melanoma cells. In a preclinical trial with one healthy dog, P38Bf administration did not induce adverse effects over approximately 2 months. In phase I/II clinical trials of three dogs with malignant melanoma, one dog vomited, and all dogs had increased serum levels of C-reactive protein, although all adverse effects were grade 1 or 2. Severe adverse effects leading to withdrawal of the clinical trial were not observed. Furthermore, one dog had stable disease with P38Bf injections. This is the first reported clinical trial of anti-PDPN antibody therapy using spontaneously occurring canine tumor models.

Claudin-2 (CLDN-2), a pore-forming tight junction protein with a tetra-transmembrane domain, is involved in carcinogenesis and the metastasis of some cancers. Although CLDN-2 is highly expressed in the tight junctions of the liver and kidney, whether CLDN-2 is a safe target for cancer therapy remains unknown. We recently generated a rat monoclonal antibody (mAb, clone 1A2) that recognizes the extracellular domains of human and mouse CLDN-2. Here, we investigated the safety of CLDN-2-targeted cancer therapy by using 1A2 as a model therapeutic antibody. Because most human therapeutic mAbs are IgG1 subtype that can induce antibody-dependent cellular cytotoxicity, we generated a human-rat chimeric IgG1 form of 1A2 (xi-1A2). xi-1A2 activated Fcγ receptor IIIa in the presence of CLDN-2-expressing cells, indicating that xi-1A2 likely exerts antibody-dependent cellular cytotoxicity. At 24 h after its intravenous injection, xi-1A2 was distributed into the liver, kidney, and tumor tissues of mice bearing CLDN-2-expressing fibrosarcoma cells. Treatment of the xenografted mice with xi-1A2 attenuated tumor growth without apparent adverse effects, such as changes in body weight and biochemical markers of liver and kidney injury. These results support xi-1A2 as the lead candidate mAb for safe CLDN-2-targeted cancer therapy., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The production of antibodies against the extracellular regions (ECR) of multispanning membrane proteins is notoriously difficult because of the low productivity and immunogenicity of membrane proteins due to their complex structure and highly conserved sequences among species. Here, we introduce a new method to generate ECR-binding antibodies utilizing engineered liposomal immunogen prepared using a wheat cell-free protein synthesis system. We used claudin-5 (CLDN-5) as the target antigen, which is a notoriously difficult to produce and poorly immunogenic membrane protein with two highly conserved extracellular loops. We drastically improved the productivity of CLDN-5 in the cell-free system after suppressing and normalizing mRNA GC content. To overcome its low immunogenicity, two engineered antigens were designed and synthesized as proteoliposomes: a human/mouse chimeric CLDN-5, and a CLDN-5-based artificial membrane protein consisting of symmetrically arranged ECRs. Intraperitoneal immunization of both engineered CLDN-5 ECR antigens induced ECR-binding antibodies in mice with a high success rate. We isolated five monoclonal antibodies that specifically recognized CLDN-5 ECR. Antibody clone 2B12 showed high affinity (<10 nM) and inhibited CLDN-5-containing tight junctions. These results demonstrate the effectiveness of the methods for monoclonal antibody development targeting difficult-to-produce membrane proteins such as CLDNs.

The 27-member family of tetraspan membrane proteins known as claudins (CLDNs) is a major component of tight junctions. A series of studies elucidating the relationship between CLDNs and various pathological conditions has provided new insights into drug development. For instance, CLDN-1 may be a potent target for epidermal absorption of drugs and for treating hepatitis C virus (HCV) infection. CLDN-4 may be a target for treating cancer. Because CLDNs are also expressed in various normal tissues, safety and efficacy evaluations are critical for translational research. We previously developed several anti-CLDN antibodies and have established proof of concept for CLDN-targeted drug development using these reagents. Here, we provide an overview of CLDN-1 as a target for improving epidermal drug absorption and preventing HCV infection and of CLDN-4 as a target for anticancer therapeutics., (© 2017 New York Academy of Sciences.)

Claudins (CLDNs) are a 27-member family of tetra-transmembrane proteins that have pivotal roles in maintaining cellular polarity and sealing the spaces between adjacent cells. Deregulation of their functions is often associated with pathological conditions, including carcinogenesis and inflammation. Some CLDNs are co-receptors for hepatitis C virus. Because CLDN-driven regulation of intercellular seals might be manipulated to enhance drug absorption, CLDNs are attractive targets for drug development. Monoclonal antibodies recognizing the extracellular domain of CLDNs are the first choice for therapeutics, but their development has been delayed. Here, we overview recent advances in the creation of anti-CLDN antibodies and discuss CLDNs as drug development targets., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Claudin-1 (CLDN-1), an integral transmembrane protein, is an attractive target for drug absorption, prevention of infection, and cancer therapy. Previously, we generated mouse anti-CLDN-1 monoclonal antibodies (mAbs) and found that they enhanced epidermal absorption of a drug and prevented hepatitis C virus infection in human hepatocytes. Here, we investigated anti-tumor activity of a human-mouse chimeric IgG1, xi-3A2, from one of the anti-CLDN-1 mAbs, clone 3A2. Xi-3A2 accumulated in the tumor tissues in mice bearing with human CLDN-1-expressing tumor cells. Xi-3A2 activated Fcγ receptor IIIa-expressing reporter cells in the presence of human CLDN-1-expressing cells, suggesting xi-3A2 has a potential to exhibit antibody-dependent cellular cytotoxicity against CLDN-1 expressing tumor cells. We also constructed a mutant xi-3A2 antibody with Gly, Ser, and Ile substituted with Ala, Asp, and Arg at positions 236, 239, and 332 of the Fc domain. This mutant antibody showed greater activation of Fcγ receptor IIIa and in vivo anti-tumor activity in mice bearing human CLDN-1-expressing tumors than xi-3A2 did. These findings indicate that the G236A/S239D/I332E mutant of xi-3A2 might be a promising lead for tumor therapy., (Copyright © 2016 Elsevier Inc. All rights reserved.)

PEGylation, the attachment of polyethylene glycol (PEG) to nanocarriers and proteins, is a widely accepted approach to improving the in vivo efficacy of the non-PEGylated products. However, both PEGylated liposomes and PEGylated proteins reportedly trigger the production of specific antibodies, mainly IgM, against the PEG moiety, which possibly leads to a reduction in safety and therapeutic efficacy of the PEGylated products. In the present study, two monoclonal anti-PEG IgMs--HIK-M09 via immunization with an intravenous injection of PEGylated liposomes (SLs) and HIK-M11 via immunization with a subcutaneous administration of PEGylated ovalbumin (PEG-OVA) were successfully generated. The generated IgMs showed efficient reactivity to mPEG2000 conjugated to 1,2-distearoyl-sn-glycero-3-phospho-ethanolamine (DSPE), PEGylated liposome (SL) and PEG-OVA. It appears that HIK-M09 recognizes ethoxy (OCH₂CH₂) repeat units along with a terminal motif of PEG, while HIK-M11 recognizes only ethoxy repeat units of PEG. Such unique properties allow HIK-M09 to bind with dense PEG. In addition, their impact on the in vivo clearance of the PEGylated products was investigated. It was found that the generated ant-PEG IgMs induced a clearance of SL as they were intravenously administered with SL. Interestingly, the HIK-M11, generated by PEG-OVA, induced the clearance of both SL and PEG-OVA, while the HIK-M09, generated by SL, induced the clearance of SL only. We here revealed that the presence of serum anti-PEG IgM and the subsequent binding of anti-PEG IgM to the PEGylated products are not necessarily related to the enhanced clearance of the products. It appears that subsequent complement activation following anti-PEG IgM binding is the most important step in dictating the in vivo fate of PEGylated products. This study may have implications for the design, development and clinical application of PEGylated products and therapeutics., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: CD44 is a major cellular receptor for hyaluronic acids. The stem structure of CD44 encoded by ten normal exons can be enlarged by ten variant exons (v1-v10) by alternative splicing. We have succeeded in preparing MV5 fully human IgM and its class-switched GV5 IgG monoclonal antibody (mAb) recognizing the extracellular domain of a CD44R1 isoform that contains the inserted region coded by variant (v8, v9 and v10) exons and is expressed on the surface of various human epithelial cancer cells., Methods and Principal Findings: We demonstrated the growth inhibition of human cancer xenografts by a GV5 IgG mAb reshaped from an MV5 IgM. The epitope recognized by MV5 and GV5 was identified to a v8-coding region by the analysis of mAb binding to various recombinant CD44 proteins by enzyme-linked immunosorbent assay. GV5 showed preferential reactivity against various malignant human cells versus normal human cells assessed by flow cytometry and immunohistological analysis. When ME180 human uterine cervix carcinoma cells were subcutaneously inoculated to athymic mice with GV5, significant inhibition of tumor formation was observed. Furthermore, intraperitoneal injections of GV5markedly inhibited the growth of visible established tumors from HSC-3 human larynx carcinoma cells that had been subcutaneously transplanted one week before the first treatment with GV5. From in vitro experiments, antibody-dependent cellular cytotoxicity and internalization of CD44R1 seemed to be possible mechanisms for in vivo anti-tumor activity by GV5., Conclusions: CD44R1 is an excellent molecular target for mAb therapy of cancer, possibly superior to molecules targeted by existing therapeutic mAb, such as Trastuzumab and Cetuximab recognizing human epidermal growth factor receptor family.

Tissue factor (TF), the initiating cell surface receptor for the blood coagulation cascade, plays an important role in malignant transformation of the pancreas, although the precise mechanism remains unresolved. Here, we report that the TF - factor VIIa complex in human pancreatic cancer cells produced a significant amount of MMP-9 and promoted invasion ability in vitro and invasion and metastasis in vivo. For treatment, we successfully developed an anti-human TF monoclonal antibody that inhibits both cellular signalling and blood coagulation cascade via TF. Invasive capability and MMP-9 expression were significantly reduced by the antibody. The antibody inhibited not only tumour invasion in the orthotopic model, but also haematogenous metastasis in the portal-injection liver metastasis model. In conclusion, the TF-VIIa complex plays an important role in invasion-metastasis by enhancing tumour cell infiltration ability and forming microthrombi. The newly established anti-human TF neutralisation antibody may be useful for the treatment of pancreatic and other invasive cancers., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Cell-surface molecules containing growth factor receptors, adhesion molecules and transporter proteins are often over-expressed in various cancer cells, and could be regarded as suitable targets for therapeutic monoclonal antibodies (mAb). Anti-cancer therapeutic mAb are claimed to bind these cell-surface molecules on viable cancer cells: therefore, it is necessary to produce mAb recognizing epitopes on the extracellular domains of native but not denatured proteins. We have experienced difficulty in obtaining mAb bound to viable cancer cells using synthetic peptides or recombinant proteins produced in bacteria as immunogens, although these immunogens are relatively easy to prepare. In this context, we have concluded that viable cancer cells or cells transfected with cDNA encoding target proteins are suitable immunogens for the production of anti-cancer therapeutic mAb. Furthermore, we selected rats as the immunized animals, because of their excellent capacity to generate diverse antibodies. Because many target candidates are multi-pass (type IV) membrane proteins, such as 7-pass G protein-coupled receptors and 12-pass transporter proteins belonging to the solute carrier family, and their possible immunogenic extracellular regions are very small, production of specific mAb was extremely difficult. In this review, we summarize the successful preparation and characterization of rat mAb immunized against the extracellular domain of type I, type II and type IV membrane oncoproteins fused to green fluorescent protein as an approach using reverse genetics, and also introduce the discovery of cell-death-inducing antibodies as an approach using forward genetics and a strategy to produce reshaped antibodies using mimotope peptides as the immunogen., (© 2010 Japanese Cancer Association.)

We obtained unique cell-death-inducing monoclonal antibodies (mAbs) named D18 and D19 against chicken DT40 cells. D18 and D19 caused several signs of apoptosis, such as exposed phosphatidyl serine on the cell surface, a sub G(0)/G(1) peak, and DNA fragmentation, and inhibited the proliferation of DT40 cells. Flow cytometric and immunohistological analyses of various normal chicken tissues revealed the expression of the antigen recognized by these mAbs to be restricted to cells in lymphoid organs including bone marrow and bursa of fabricius, and to cells in some epithelial tissues. The cell death induced by the mAbs progressed through a mitochondrial pathway with loss of mitochondrial membrane potential. Apoptosis is generally characterized by cell shrinking; however, D18 and D19 elicited swelling, which preceded the cell death. We analyzed the antigen immunoprecipitated by the mAbs, and identified a 90- to 100-kDa cell-surface glycoprotein as the chicken transferrin receptor (TfR). Epitopes recognized by the two mAbs were confirmed to be different by the binding inhibition assay. The reactivity of the mAbs against DT40 cells was not inhibited by excess chicken serum, suggesting that the cell death induced by D18 and D19 was not caused by inhibition of the binding of transferrin (Tf) to chicken TfR. Since D18 and D19 have induced cell death in human embryonic kidney cells transfected with cDNA of the full-length chicken TfR, we expect human TfR to be a promising target in antibody therapy for various human malignancies.

L-type large amino acid transporter (LAT) 1, the first light chain (lc) of cluster of differentiation 98 (CD98) to be identified, is associated with the heavy chain (hc) of CD98 and expressed on the surface of various tumor cells irrespective of their origin. Because LAT1 is a 12-pass membrane protein and its possible immunogenic extracellular region is very small, specific monoclonal antibodies (mAb) had not been developed. We report the successful preparation and characterization of mAb recognizing the extracellular domain of human LAT1 protein. Two mAb were selected from hybridoma clones established by fusing mouse myeloma cells and spleen cells from rats immunized against RH7777 rat hepatoma cells expressing recombinant green fluorescent protein fused to human LAT1 protein. Designated SOL22 and SOL69, these mAb specifically reacted with the extracellular domain of LAT1 on cells transfected with cDNA of LAT1, but not with cells transfected with cDNA of other CD98 lc, namely, LAT2, y(+)LAT1, y(+)LAT2, and xCT amino acid transporters. These mAb immunoprecipitated 35- and 90-kDa proteins under reducing conditions in extracts prepared from human HeLa tumor cells, indicating the existence of intermolecular disulfide bonds between cysteine residues in the 90-kDa hc and 35-kDa lc (LAT1). SOL22 and SOL69 mAb reacted with a wide variety of living unfixed human tumor cell lines, but were only weakly reactive with HEK293F human embryonic kidney cells and human peripheral blood cells. Comparative immunohistochemical analyses of normal human tissues with anti-CD98 hc and anti-LAT1 revealed LAT1 to be an excellent molecular target for antibody therapy, possibly even superior to CD98 hc.

Programmed cell death (PCD) is categorized as apoptotic, autophagic, or necrosis-like. Although the possibility that plural (two or three) death signals could be induced by a given stimulus has been reported, the precise mechanisms regulating PCD are not well understood. Recently, we have obtained two anti-chicken transferrin receptor (TfR) monoclonal antibodies (mAbs; D18 and D19) inducing a unique cell death. Although the cell death had several features of apoptosis, autophagic and necrosis-like morphological alterations were simultaneously observed in electron microphotographs. In addition to cells with condensed chromatin and an intact plasma membrane (apoptotic cells), cells having many vacuoles in the cytoplasm (autophagic cells), and enlarged cells with ruptured plasma membranes (necrosis-like cells) were observed in DT40 cells treated with the mAbs, however, the latter two types of dead cells were not detected upon treatment with staurosporine, a typical apoptosis inducer. In autophagic cells, numerous membrane-bound vesicles occupying most of the cytoplasmic space, which frequently contained electron-dense materials from cytoplasmic fragments and organelles, were observed. The simultaneous induction of multiple death signals from a stimulus via the TfR is of great interest to those researching cell death. In addition, activation of caspases was observed in DT40 cells treated with D19, however, the cell death was not inhibited with z-VAD-fmk, a pan-caspase inhibitor, suggesting that at least in part, a caspase-independent pathway is involved in the TfR-mediated cell death.

Although antitumor necrosis factor (anti-TNF)-alpha therapy provides beneficial effects on various chronic inflammatory skin diseases including psoriasis, cutaneous side-effects have also been reported. We describe four patients who showed psoriasiform eruption following anti-TNF-alpha therapy (infliximab) for Crohn's disease. In all patients, Crohn's disease had responded well to infliximab. Three patients developed plaque-type psoriasiform eruption on the trunk and four extremities, while one patient showed pustular eruption on the palms and soles accompanied with plaque-type psoriasis. In all these patients, skin lesions subsided with topical application of corticosteroid ointment or psoralen plus ultraviolet A treatment.

Sialic acid (Sia) is a family of acidic nine-carbon sugars that occupies the nonreducing terminus of glycan chains. Diversity of Sia is achieved by variation in the linkage to the underlying sugar and modification of the Sia molecule. Here we identified Sia-dependent epitope specificity for GL7, a rat monoclonal antibody, to probe germinal centers upon T cell-dependent immunity. GL7 recognizes sialylated glycan(s), the alpha2,6-linked N-acetylneuraminic acid (Neu5Ac) on a lactosamine glycan chain(s), in both Sia modification- and Sia linkage-dependent manners. In mouse germinal center B cells, the expression of the GL7 epitope was upregulated due to the in situ repression of CMP-Neu5Ac hydroxylase (Cmah), the enzyme responsible for Sia modification of Neu5Ac to Neu5Gc. Such Cmah repression caused activation-dependent dynamic reduction of CD22 ligand expression without losing alpha2,6-linked sialylation in germinal centers. The in vivo function of Cmah was analyzed using gene-disrupted mice. Phenotypic analyses showed that Neu5Gc glycan functions as a negative regulator for B-cell activation in assays of T-cell-independent immunization response and splenic B-cell proliferation. Thus, Neu5Gc is required for optimal negative regulation, and the reaction is specifically suppressed in activated B cells, i.e., germinal center B cells.

To investigate the molecular structural and functional characteristics of tumor-suppressive anti-ErbB-2 monoclonal antibody (mAb) SER4, we performed mAb-gene cloning and epitope mapping by a phage display system. Structural analysis demonstrated that both the heavy chain (HC) and light chain variable regions are highly homologous with the derived germline sequences, while the HC complementarity determining region (HCDR) 3 has a relatively short length and biased amino acid usage. A cloned gene-derived recombinant Fab (rFab) fragment showed antigen binding activity and specificity comparable to the parent mAb. Cross-linking of the rFab fragment with the anti-Fab antibody elicited cell growth inhibition in vitro. These results imply that the cloned genes actually encode the Fab part of SER4. The epitope mimetic peptide (mimotope) isolated by panning a phage-displayed random peptide library against SER4 showed no cross-reactivity with mAbs other than SER4. The mimotope was found to be homologous with (87)AHNQVRQVPLQR(98) in the extracellular domain of ErbB-2 by means of a clustalw search. Since SER4 causes the growth inhibition of ErbB-2 positive cells, the predicted epitope sequence may constitute the putative functional domain of ErbB-2.

The Fab gene of anti-CD98 heavy chain (h.c.) monoclonal antibody (mAb) HBJ127 was cloned and expressed as a recombinant Fab (rFab) fragment by means of a phage display system. The variable heavy and light chain genes of HBJ127 were found to be derived from VOx-1 and IgVk8-30 germline, respectively. Extensive somatic mutation was found in the heavy chain complementarity determining region 2. rFab fragment was purified homogeneously from crude bacterial lysates by Ni-chelate chromatography in a yield of 71.4 mg from 100 ml of culture. rFab fragment was reactive with the cell surface of CD98-positive cells irrespective of tissues of origin, but not with CD98-negative cells. The recognition site of the rFab fragment was identical to that of mAb since the binding of rFab fragment to HeLaS(3) cells was completely inhibited by pretreatment with an excess of mAb. The relative affinity values of rFab fragment and mAb were found to be 0.11 x 10(8) and 0.35 x 10(8) M(-1), respectively. Three-fold lower affinity of rFab fragment may be due to the difference of valency of the antibody preparation. Cell growth inhibition in vitro by rFab fragment preincubated with anti-Fab suggests that the rFab fragment produced by cloned gene-bearing Escherichia coli was identical to the Fab part of HBJ127 mAb. These results show that a small fragment with antigen binding activity similar to that of the parent mAb can easily be prepared by using a phage display system. To our knowledge, this is a first report of the production of anti-CD98 h.c. rFab fragment.

Twenty kilodalton human growth hormone (20K-hGH) is a naturally occurring isoform lacking amino acid residues 32-46 of 22K-hGH. Due to this structural similarity to 22K-hGH, no one has constructed a specific and sensitive assay system for 20K-hGH, which can be used for measuring physiological concentration of this isoform in the circulation. To construct such a specific assay system, we have generated polyclonal antibodies (pAb) and monoclonal antibodies (mAbs) against recombinant 20K-hGH. Binding characteristics to 20K-, 22K-hGH and monkey GH (mGH) of these five mAbs, designated A23, B13, C02, D05, and D14, were analyzed by enzyme immunoassays (EIAs) and surface plasmon resonance analysis. Only one of them, the mAb D05, does not crossreact with 22K-hGH. It was also observed that mAb B13 does not crossreact with mGH, although the later is 96% homologous to hGH. Using these antibodies we have established several sandwich EIA systems for circulating 20K-hGH. The combination of A23 as a solid-phase antibody and B13 as a labeled antibody permitted both high sensitivity to 20K-hGH (< 0.1 ng/ml) and low cross-reactivities with 22K-hGH (< 2%), mGH (< 0.3%) and rat GH (< 0.1%). The clearances of administered 20K-hGH were determined by this combination in both rats and monkeys. In the assay of physiologically circulating 20K-hGH in humans, the combination of D05 and affinity-purified anti-20K-hGH pAb showed the highest sensitivity to 20K-hGH (< 10 pg/ml) and substantially no cross-reactivity with 22K-hGH (< 0.1%). The plasma 20K-hGH concentration in healthy female subjects was determined by this combination. The assay systems constructed here enables us to directly measure circulating 20K-hGH in physiological condition with no interference of 22K-hGH for the first time.

The pre-T-cell receptor (TCR) complex, which consists of a heterodimer of the TCR beta-chain and the pre-TCR alpha-chain, is known to regulate early thymocyte development. The pre-TCR complex contains CD3 subunits as a signal-transducing molecule, but the exact subunit composition of the fully assembled pre-TCR complex remains to be elucidated. In particular, the association of the CD3 zeta-chain with the pre-TCR is controversial. In the present study, we have generated a monoclonal antibody against the cytoplasmic portion of the pre-TCR alpha-chain, and analysed a subunit composition of the pre-TCR complex. We demonstrated that the CD3 zeta-chain is physically associated with the pre-TCR in immature T cells. Thus, the result strongly supports the previous findings that CD3 zeta contributes to signalling mediated through the pre-TCR complex.

A monoclonal antibody was produced by immunizing BALB/c mice with freshly prepared canine thymocytes and peripheral blood leukocytes. The antibody, designated 59.4, was of the IgG1 subclass type and mainly reacted with lymphocytes. In single-color flow cytometric analysis, lymphocytes from the peripheral blood, thymus and spleen were graded into three categories according to their fluorescence intensity labeling by antibody 59.4: weakly, moderately and intensely positive cells. Two-color analysis revealed that a major population of CD8-positive cells were intensely labeled by antibody 59.4, but less than 50% of CD4-positive cells were moderately reacted with antibody 59.4. Immunohistochemically, thymocytes in the medulla showed moderately intense immunoreactivity to 59.4, but most lymphocytes in the cortex were negative in reaction. Immunostaining using antibody 59.4 demonstrated characteristic aggregations of 59.4-positive lymphocytes in the reticulum cell-free region of the thymic medulla. In the spleen, scattered lymphocytes in the outer layer of the marginal zone and in the red pulp were intensely labeled by antibody 59.4, while lymphocytes gathering in the mantle zone and periarterial lymphatic sheath (PALS) were moderately stained. Antibody 59.4 appears to recognize an antigen which is expressed by a more-differentiated T cell-lineage but not by immature T cells in the thymic cortex.

Monoclonal antibodies were produced by immunizing BALB/c mice with freshly prepared canine thymocytes and peripheral blood leukocytes. Flow cytometric analysis of canine peripheral blood leukocytes showed that an antibody, designated 169.1, recognized about 60% of non-lymphoid cells, but reacted with less than 3% of lymphocytes. Immunohistochemistry using frozen sections showed that several types of epithelial cells such as epithelial reticulum cells in the thymus and ductal system in the parotid gland exhibited an intense positive reaction to antibody 169.1. Moreover, the ellipsoidal sheath in the spleen and non-myelinated nerve fibers in the peripheral nervous system had selectively positive reactions; in the latter, filamentous structures were visible under a light microscope. In contrast to the data from the flow cytometric analysis, no leukocytes on sections reacted with 169.1. Immunoblot assay revealed that 169.1 recognized antigens with molecular weights of 48 and 52 kDa under reducing conditions. These findings characterize 169.1 as an antibody against a cytoskeletal protein rich in epithelial cells and neurons.

We previously generated a monoclonal antibody (mAb) against a putative pathogenic epitope on native type II collagen (CII) for the induction of collagen-induced arthritis in mice (mAb1), and an anti-idiotypic mAb which appears to possess the internal image of the CII epitope (mAb2). In the present study, the structural basis of the antigen/mAb1 and mAb1/mAb2 interactions was examined. When partially SH-reduced mAb1 was analysed on Western blots, only fragments containing both heavy (H) and light (L) chains were recognized by mAb2. When mAb2 was partially SH-reduced, only fragments containing both H and L chains were recognized by mAb1. H and L chains were separated from mAb1 in a reduced, denatured condition, and each chain and a mixture of the two were refolded. mAb2 reacted specifically to the renatured whole IgG molecule of mAb1, but not to the refolded L or to H chains. Recombinant single chain Fv (scFv) generated from mAb1 and mAb2 had properties of the original mAbs, whereas genetically constructed chimeric scFvs, consisting of VH from mAb1 and an irrelevant VL. or VL of mAb1 and an irrelevant VH. did not react either to CII or to mAb2. Thus, interactions among CII, mAb1 and mAb2 appear to depend on quaternary structures containing different protein subunits. These observations support the internal image property of the mAb2. In addition, this dependency on quaternary structure for recognition of proteins may also be relevant to other protein-protein interactions.

Anti-intercellular adhesion molecule-1 (anti-ICAM-1) and anti-lymphocyte-function-associated antigen-1 (anti-LFA-1) monoclonal antibodies (mAbs) were injected into mice and their effects on tumor metastasis were investigated using two murine models. Depending on the dose, the anti-ICAM-1 mAb (KAT-1) expressed both inhibitory and promoting effects on liver metastases of ICAM-1 + LFA-1 + P815 mastocytoma cells, whereas it enhanced lung metastases of the ICAM-1-LFA-1-Meth-A fibrosarcoma cells at any doses. In contrast, anti-LFA-1 mAb (KBA) showed promoting effects only on the metastases of both tumor lines. Treatment of mice with either mAb enhanced metastases of P815 mastocytoma cells in the spleen.

Antigenic determinants (epitopes) on bovine serum albumin (BSA) to anti-BSA monoclonal antibodies (mAbs) were assessed by means of photoaffinity labeling. Anti-BSA mAbs, AB3 and AB6, were modified with an 125I-labeled photoreactive crosslinker, sulfosuccinimidyl 2-(p-azidosalicylamido)ethyl-1,3'-dithiopropionate (SASD) and then bound with BSA. The complex yielded was irradiated with UV light to facilitate covalent binding of the modified mAb with BSA. Reduction of the product with 2-mercaptoethanol revealed that radioactivity of 125I-SASD was specifically introduced into BSA, probably near the mAb combining site(s). The radiolabeled or native BSA was digested with V8 protease and the peptides produced were assessed for their amino acid sequence, the radiolabeled amino acids contained, and their reactivity to mAb. The results indicated that AB3 mAb recognized an epitope in the region of Ala-537 to Asp-554 on a linear part of the BSA molecule, whereas AB6 mAb probably recognized an epitope of the assembled form present in a peptide of Asp-299 to Glu-338.

AB-6 monoclonal antibody (mAb) against bovine serum albumin (BSA) was coupled with beta-alanine or n-propylamine using a heterobifunctional cross-linking reagent, N-(epsilon-maleimidocaproyloxy)succinimide (EMCS) and a linker, poly-L-cysteine to introduce acidic or hydrophobic groups into the mAb. The mAb molecules coupled with beta-alanine at lower than 1:16 molar ratios and those coupled with n-propylamine at 1:14 retained the original reactivity to BSA but modification with higher amounts of beta-alanine or n-propylamine decreased the reactivity. In contrast, nonspecific bindings of AB-6 mAb to a plastic culture plate and tumor (MDA-MB-453) cells were decreased by modification with beta-alanine and increased by n-propylamine. These results suggested that introduction of acidic groups, and hydrophobic groups to antibody leads to fluctuations in the non-specific binding of antibody.

Three (AB-3, AB-4 and AB-6) monoclonal antibodies (mAb) to bovine serum albumin (BSA) were derived and characterized for their physicochemical and immunological properties. AB-3 recognized an epitope distinct from epitopes recognized by AB-4 and AB-6 as determined by binding inhibition assay. AB-4 and AB-6 mAbs recognized similar but not identical epitopes on BSA. Based on the antigenic specificity, we applied these mAbs to quantitative analysis of BSA in medium and to depletion of BSA from culture medium containing fetal calf serum (FCS). For quantitative analysis, we employed a sandwich enzyme-linked immunosorbent assay (ELISA) using biotinylated AB-3, solid-phase of AB-6 and an avidin-biotin-peroxidase complex system. This assay was highly sensitive and quantitative in the range of BSA concentration at 10 to 1,500 ng/ml. To deplete BSA from medium, we prepared affinity-gel coupled to AB-6. Repeated treatment of FCS-containing medium with the affinity-gel efficiently depleted BSA from the medium. The depletion capacity was 0.74 to 1.0 moles of BSA/mole of coupled mAb.

Modification of monoclonal antibodies (mAbs) with a photo-crosslinker, sulfosuccinimidyl 2-(m-azido-o-nitrobenzamido)-ethyl-1, 3'-dithiopropionate (SAND), enhanced their antigen binding activity. By SAND modification, SV2-61 gamma mAb against human c-erbB-2 protooncogene product could immunoprecipitate approximately an 8-fold greater amount of antigen, and AB-3 mAb against bovine serum albumin (BSA) bound to BSA more efficiently than unmodified mAb as determined by an enzyme-linked immunosorbent assay. Relative binding affinity of SAND-modified AB-3 was about 4-fold of unmodified AB-3. Augmented binding of mAbs was observed with or without photosensitization.

An enzyme immunoassay (EIA) for assessment of cell activation and proliferation was developed by the use of monoclonal antibodies (MoAb) directed against a ubiquitous growth-associated antigen, gp125. Test cells distributed in a microtest plate were labeled with anti-rat gp125 MoAb, B3, for rat cells or anti-human gp125 MoAb, HBJ127, for human cells and subsequently with rabbit anti-mouse immunoglobulins. The cell-bound antibody was assessed by a colorimetric enzyme assay using horse-radish peroxidase-modified protein A and 2,2'-azinobis(3-ethylbenzthiazoline sulfonic acid). To terminate the reaction and to make the reaction mixture transparent, sodium dodecyl sulfate (SDS) was added to the mixture. The intensity of the developed color was measured by use of a multiwell scanning spectrometer. The titration curves obtained by the EIA for cells were practically similar to those obtained by the conventional 3H-thymidine (Tdr) uptake method, and the appropriate cell number to be used for the assay was indicated to be 3 to 50 x 10(3) cells per well. This method was applicable not only for quantitation of cell number of growing cells but also for measuring mitogenic responses of lymphocytes as revealed by the data obtained from Con A stimulation of lymphocytes. These results indicate that this new EIA method using anti-gp125 antibodies is useful for quantitative assays of cell growth and cell activation in the research fields of oncology and immunology.

The objective of this study was to clarify the specificity of anticardiolipin antibodies (aCL). Eighteen monoclonal hybridoma aCL from systemic lupus erythematosus (SLE)-prone MRL/Mp-lpr/lpr mice were established, and the reactivity of monoclonal aCL to phospholipids, DNA, nuclei of human epithelial cells, platelets, vascular endothelial cells, heparin, protein C and thrombomodulin was examined. All the 18 monoclonal aCL reacted with phosphatidylserine and some showed reactivity to phosphatidylinositol and phosphatidylcholine. Six of 16 monoclonal aCL were demonstrated to have the property of lupus anticoagulant. Monoclonal aCL were classified into three categories, in terms of DNA-binding specificity. Ten of 18 aCL had characteristics of antinuclear antibodies. Six of 11 aCL reacted with platelets. Three of 18 aCL were bound to vascular endothelial cells and to heparin. No monoclonal aCL reacted with protein C or thrombomodulin. Therefore, the conclusion was made that monoclonal aCL from SLE mice showed a polyspecific nature.

A monoclonal antibody (mAb) reactive with a crosslinking reagent, N-(m-maleimidobenzoyl)dipalmitoylphosphatidylethanolamine (mMBPE), in liposomes was produced from a hybridoma clone established by a fusion between P3X63Ag8.653 mouse myeloma cells and spleen cells from a BALB/c mouse hyperimmunized with the antibody-coated liposomes containing mMBPE. Using this mAb (termed AL-6), the quantity of immunoliposomes bound on target tumor cells was assessed by flow cytofluorometry. The results obtained using fluorescein isothiocyanate-coupled AL-6 allowed the enumeration not only of the immunoliposomes bound on all tumor cells but also those on individual target tumor cells. The relevance of this assay method was confirmed by a comparison with another assay method of cell-bound liposomes using immunoliposomes containing carboxyfluorescein in the vesicles.

To develop an efficient strategy for the targeting of anti-tumor effector cells, we prepared bispecific antibody (BsAb) containing anti-CD3 and an anti-c-erbB-2 proto-oncogene product. The prepared BsAb specifically reacts with both c-erbB-2-positive tumor cells and CD3+ CTL. Human CD4+ helper/killer T cells, induced from peripheral-blood mononuclear cells by activation with immobilized anti-CD3 monoclonal antibody (MAb) plus IL-2, showed no significant cytotoxicity against tumor cells. However, treatment of human CD4+ helper/killer cells with the BsAb caused the induction of specific cytotoxicity against c-erbB-2-positive tumor cells. CD4+ helper/killer cells also produced significant amounts of IL-2 during co-culture with c-erbB-2-positive tumor cells in the presence of the BsAb. Moreover, by combination with the BsAb, CD4+ helper/killer cells showed a strong in vivo anti-tumor effect against c-erbB-2 transfectant or human colon-cancer cells implanted in nude mice. Our results strongly suggest that the c-erbB-2 proto-oncogene product on human tumor cells may be a good target for BsAb-directed adoptive tumor immunotherapy.

Extraction of glycolipid component from hypertrophic and cancerous prostatic tissue were performed using chloroform-methanol solution and isopropanol-hexan-solution. The extract was separated into the "upper phase" and "lower phase" by Folchs fractionation technic. Each fraction was conjugated with acid treated salmonella minesota and than it was injected subcutaneously, intra-peritoneally and finally intravenously to BALB/c mice. Spleen cells from immunized mice were fused with P3X63, and antibody APG1 was obtained. APG1 shows a preferential reactivity towards prostatic tissue by the immunohistochemical analysis. Furthermore, the immunohistochemical analysis using enzyme and acid treated tissue and TLC immunostaining indicate that this monoclonal antibody specifically recognizes the sialylglycochain expressed in the prostatic tissue.

A monoclonal antibody termed "FR77" was obtained from a hybridoma clone established by fusion between P3x63Ag8.653 mouse myeloma cells and spleen cells of a Fischer F344 rat hyperimmune to syngeneic 9L/R3 glioma cells. Immunoperoxidase staining of various cultured cells showed that FR77 was reactive to both rat and human glioma cells, but was not reactive with other nonglioma cells. Immunohistochemical examination of paraffin-embedded or cryostat-frozen sections of various human tissues revealed that FR77 was strongly reactive with glioblastoma, grade III astrocytoma, and craniopharyngioma; partially reactive with intracerebral primitive neuroectodermal tumor, pineoblastoma, and desmoplastic medulloblastoma; and weakly reactive with low-grade astrocytoma. It was not reactive with other types of brain tumors and normal human tissues tested. The FR77-defined antigen was observed to be predominantly localized in the cytoplasm of antigen-bearing cells as suggested by the immunostaining pattern, but part of it was also expressed on the cell surface of glioma cells as demonstrated by a complement-mediated cytotoxic test. Fractionation of the antigenic component and periodic acid treatment of tumor tissue bearing the FR77-defined antigen indicated that the antigen is of a neutral glycolipid nature and that the antigenic determinant to FR77 is present on its sugar portion.

Two (MA-15C5 and MA-8D3) out of approximately 500 monoclonal antibodies, obtained by fusion of P3X63-Ag8-6.5.3 myeloma cells with spleen cells of mice immunized with purified fragment D-dimer from human fibrin, demonstrated a more than 1,000-fold higher affinity for fragment D-dimer than for native fibrinogen. MA-15C5 was directed against a neoantigenic determinant only expressed in fragment D-dimer. MA-8D3 reacted equally well with fragment D-dimer of crosslinked fibrin and with fragment D of non-crosslinked fibrin but not with fragment D of fibrinogen. Both monoclonal antibodies did not crossreact with rabbit fibrin and its degradation products. The binding of 125I-labeled Fab fragments to human plasma clots, introduced and aged for 1 hr in the jugular vein of heparinized rabbits was studied. Following injection of an equimolar mixture of Fab fragments derived from MA-15C5 and MA-8D3, the clot to blood ratios of radioactivity increased from 3.2 +/- 1.2 (mean +/- SD) at 4 hr to 7.2 +/- 1.4 at 17 hr. The binding of Fab fragments of MA-15C5 and MA-8D3 was independent of the age (1 to 72 hrs) of the clot and of heparin anticoagulation and was only slightly decreased (by 20%) in the presence of circulating human fibrinogen (90 mg/kg body weight) and of human cross-linked fibrin degradation products at a plasma concentration of 10 micrograms/ml. The binding of Fab fragments of MA-15C5 and MA-8D3 to occlusive human plasma clots in the femoral artery of rabbits was comparable to that of the non-occlusive human plasma clots in the jugular vein.(ABSTRACT TRUNCATED AT 250 WORDS)

B3 murine IgG1 monoclonal antibody against BC47 rat bladder cancer detected an antigen distributed on the cell surface of neoplastic cells and proliferating normal tissue cells. The percentage of B3 antigen-positive cells in lymphocytes was increased by mitogen stimulation. The molecular weight of the antigen was 130,000 or 140,000 daltons.

F(ab')2 fragments of a murine monoclonal anti-platelet GPIIb/IIIa antibody (7E3) are a potent platelet aggregation inhibitor, which in a canine coronary artery thrombosis model accelerate lysis with recombinant tissue-type plasminogen activator (rt-PA) and prevent reocclusion (7). In the present study, we have investigated the potential value of platelet aggregation inhibition as adjunctive therapy to lysis of venous thrombi, by measuring the thrombolytic potency of 7E3-F(ab')2 and rt-PA used alone or in combination, in dogs with a 125I-fibrin labeled femoral vein thrombus. The dose-response of thrombolysis with rt-PA infused over 4 hours was linear: doses of 0.075 mg/kg, 0.15 mg/kg and 0.3 mg/kg produced 37 +/- 3, 57 +/- 11 and 83 +/- 4% lysis respectively, against a background value of 20 +/- 2%. With F(ab')2 fragments of 7E3 given as a bolus of 1.2 mg/kg, which saturated 70% of the platelet GPIIb/IIIa receptors and prolonged the bleeding to more than 30 min, lysis was not significantly increased over background. Combination of 0.3 or 0.6 mg/kg of 7E3-F(ab')2 with either 0.03 or 0.06 mg/kg of rt-PA did not produce more lysis than obtained with a comparable dose of rt-PA alone. No significant changes in plasma fibrinogen or alpha 2-antiplasmin were observed with either agent alone or with the combination. It is concluded that extensive inhibition of platelet aggregation does not potentiate the thrombolytic effect of rt-PA in this venous thrombosis model.

Fischer 344 (F344) rats hyperimmunized with syngeneic 9L/R3 glioma cells produced antibody selective to glioma cells. Hybridomas prepared from the spleen cells of the immunized rat were cloned, and we obtained a hybridoma clone which produced monoclonal IgM antibody, termed FR77, that showed selectivity to glioma cells. Immunoperoxidase staining of cultured cells revealed that FR77 was reactive with 3 lines of rat glioma cells but not with normal F344 rat fibroblasts. Immunohistochemical staining of F344 rat tissue sections with biotinylated FR77 demonstrated that FR77 could bind with glioma tissue developed by intracerebral injection of 9L/R3 glioma cells but not to normal parts of the brain tissues and other normal tissues tested. The FR77-defined antigen was observed to be mainly localized in cytoplasm of glioma cells but a small portion of the antigen was also detected on the glioma cell surface.

Monoclonal antibodies (MAbs) were obtained from hybridoma clones established by cell fusion between P3X63Ag8.653 mouse myeloma cells and spleen cells of mice or rats hyperimmunized against human bladder cancer tissue or BC47 rat bladder cancer cells. RBS-31 and RBS-85 mouse MAbs and RBA-1 rat MAb were raised against BC47 cells and HBP-1 MAb was raised against human bladder cancer tissues. Urinary antigens detected by these MAbs were quantitatively assayed by means of ELISA using 50 microliters of 1:2 diluted urine samples. The cut-off value of the assay was set up as the mean + 4 X SD of the mean using data from the healthy individual urine samples. The reactivity of all healthy control urine samples were under the cut-off value (negative). By contrast, urine from bladder cancer patients reacted positively with the RBS-31 MAb at 72%, with the RBS-85 MAb at 63%, with the RBA-1 MAb at 51% and with the HBP-1 MAb at 35%. The urine samples from some patients with renal calculi, acute cystitis or complicated urinary tract infections showed only a weak reactivity with our MAbs. As for extra-bladder cancers, some patients with renal, renal pelvis, prostate or ureter cancer, but no patients with esophageal, gastric, colon or liver cancer or leukemia, had reactive urinary antigens.

Monoclonal antibodies HBJ127 and HBJ8, raised against T24 human bladder cancer cells, predominantly react with the cells in proliferating stages and with a portion of epithelial tumor cells, respectively. To investigate the in vivo localization of these monoclonal antibodies, the antibodies were labeled with radioiodine and indium-111 (111In) and injected into nude mice transplanted with human bladder tumors. The BT-11 bladder tumor had the highest concentration of radioiodinated HBJ127 and HBJ8 monoclonal antibodies, with 11.6 and 14.3% of the injected dose per gram and with a tumor-to-blood ratio of 2.6 and 1.6, respectively, at 4 days after the administration. An irrelevant monoclonal antibody did not show any specific accumulation in the BT-11 tumor. The 111In-labeled HBJ127 antibody was also localized in the tumor with a higher tumor-to-blood ratio than the radioiodinated antibody. The xenografted BT-11 tumor was successfully visualized with the radiolabeled HBJ127 and HBJ8 antibodies by scintigraphy. These monoclonal antibodies and the human bladder tumor xenografts may provide a good model for radioimmunoimaging and possibly therapy.

A murine IgM monoclonal antibody, designated SV2-61, was generated against human c-erbB-2 gene-transfected NIH-3T3 (SV11) cells. SV2-61 defined a 185-kDa molecule present on the surface of SV11 cells, another line of c-erbB-2 gene-transfected NIH-3T3 (A4-15) cells, and MKN-7 human gastric cancer cell line carrying an amplified human c-erbB-2 gene. The SV2-61-defined antigen was found to show protein kinase activity in vitro. The SV2-61 was reactive with human c-erbB-2 gene-transfected NIH-3T3 cell lines but not with transfectants carrying c-erbB-2 gene mutants which lack a coding region for the extracellular domain. It was reactive with a portion of human epithelial cell lines but not with native NIH-3T3, TGF-alpha-coding gene-, activated c-raf gene- or Ha-ras gene-transfected NIH-3T3 cells, or non-epithelial human cells. These results indicate that the SV2-61 is an antibody which recognizes an extracellular domain of the c-erbB-2 gene product, 185-kDa protein.

The mouse monoclonal antibody (MoAb) B3 raised against a rat bladder cancer cell line and the MoAbs HBJ127 and HBJ98 raised against a human bladder cancer cell line recognize homologous antigens predominantly present on proliferating cells of the corresponding species. Examination of MoAb-defined antigen and epitopes revealed that both HBJ127 and HBJ98 MoAbs defined a human cell surface glycoprotein complex having an apparent molecular weight of 125,000-130,000 which was composed of a heavy subunit of a glycoprotein nature (Mr 90,000-95,000) and a disulfide-linked light subunit of protein nature (Mr 30,000-35,000), but the HBJ127 and HBJ98 MoAbs recognized a protein epitope and a sugar epitope on the heavy subunit, respectively. Likewise, the B3 MoAb recognized a protein epitope on the heavy subunit of a rat cellular glycoprotein complex of similar composition to the HBJ127/HBJ98-defined human antigen. Addition of the B3 MoAb to rat and the HBJ127 or HBJ98 MoAb to human tumor cells inhibited the nucleic acid synthesis or the proliferation of the tumor cells in vitro in a dose-dependent manner. The target tumor cells exposed to MoAb could regrow when they were freed from the antibody, indicating that the effect of these MoAbs on the tumor cells is cytostatic and reversible. These MoAbs did not cause down-regulation of the cell surface antigen and did not arrest the cell cycle in a certain phase. These observations indicate that the Mr 125,000 glycoprotein cell surface component detected in both rat and human systems may play a requisite role for cell proliferation and that our MoAbs could inhibit the function by binding to the functionally proximal region of the component.

SH-bearing subunits of IgM antibody were coupled through the Fc portion to sonicated liposomes consisting of N-(m-maleimidobenzoyl)dipalmitoylphosphatidylethanolamine, dipalmitoylphosphatidylcholine and cholesterol. Liposomes coated with subunits of monoclonal IgM antibody against a mouse mammary tumor-associated antigen selectively bound to the antigenic target cells. Assays of the liposomes for complement dependent cytotoxicity and spleen cell binding revealed inactivation of the liposome-coupled antibodies in both assays.

Monoclonal antibody-drug conjugates were applied as a clinical trial for patients who, based on the experimental study, had colorectal cancer. Monoclonal antibody A7, from a mouse splenocyte immunized against human colon cancer, was used as a drug carrier for colon cancer. The anti-cancer drugs mitomycin C (MMC) and neocarzinostatin (NCS) were bound covalently to A7 to form the conjugates A7-MMC and A7-NCS. The in vitro cytotoxic effects of the conjugates on SW1116 cells were stronger than those on free MMC or NCS. The conjugate A7-NCS, when administered to nude mice, brought about the highest NCS tumor concentration, whereas normal immunoglobulin G (IgG)-NCS distributed evenly in all tissues. The conjugates showed a strong antitumor effect on colon cancer transplanted into nude mice. Forty-one patients with colorectal cancer, including ten patients with postoperative metastasis, were given A7-NCS. The immunoperoxidase and drug concentration studies of the resected specimens showed that NCS was localized specifically in cancer. Patients receiving the conjugate did not experience serious adverse effects. Of the eight patients with postoperative liver metastasis, three showed evidence of tumor reduction on computed tomography (CT) scan and three claimed pain relief. The conjugate did not benefit patients with multiple lung metastasis or peritoneal metastasis.

Sonicated liposomes containing actinomycin D in the membranes were chemically coated with the subunits of monoclonal immunoglobulin M (IgM) antibody against a mouse mammary tumor-associated antigen (MM antigen) and examined for their in vitro and in vivo antitumor effects against MM46 (MM+) and MM48 (MM-) tumors of C3H/He mouse origin. The antibody-bearing, actinomycin D-containing liposomes (chemoimmunoliposomes) were selectively bound to MM+ tumor cells and showed much more in vitro cytotoxicity against the tumor cells than that shown by free actinomycin D. The in vivo antitumor effect of the chemoimmunoliposomes was tested on the mammary tumor cells (5 X 10(4) to 5 X 10(6) transplanted i.p. into syngeneic mice. A single i.p. injection of the chemoimmunoliposomes containing 0.3, 0.5, or 1 microgram of actinomycin D into MM46 tumor-bearing mice resulted in the cure of some mice and a prolonged survival time in the rest of the mice as compared to results in controls. In this test, free actinomycin D, anti-MM IgM antibody, and bovine serum albumin-coated liposomes containing actinomycin D were marginally effective or ineffective. To examine a systemic antitumor effect of chemoimmunoliposomes, mice were inoculated with MM46 tumor cells and then treated with a single i.v. injection of liposomes 4 days later. If the mice were pretreated with an i.v. injection of unmodified multilamellar liposomes, an injection of the chemoimmunoliposomes containing 1 microgram of actinomycin D resulted in a significant inhibition of tumor growth. Both free actinomycin D and bovine serum albumin-coated liposomes containing actinomycin D were ineffective against the s.c. tumor. These results indicate that an antitumor drug entrapped in the membranes of small sonicated liposomes bearing antitumor monoclonal antibodies can be delivered to antigenic tumor cells and exert more efficient antitumor activity than does the free drug.

Monoclonal antibody S202 reactive with scirrhous gastric carcinoma cell line MK-01 was used in an immunoperoxidase assay to characterize the antigenic profile of a variety of fixed samples. Representative sections of malignant tissue from the stomach, colon, esophagus, pancreas, bile duct, gallbladder and breast were examined by the avidin-biotin complex immunoperoxidase technique and compared. The antibody reacted with 90 out of 98 stomach adenocarcinomas, and with 30 out of 32 colon adenocarcinomas with diffuse cytoplasmic staining, whereas it reacted with only 19 out of 37 breast carcinomas, and 5 out of 10 esophageal squamous cell carcinomas. The antigenic determinants appeared to be a carbohydrate, since it was highly sensitive to sodium periodate.

The addition of monoclonal killer blocking antibodies (KBA MAb) to cultured T cells resulted in significant inhibition of T-cell responses to concanavalin A (Con A), class I antigen and class II antigen, whereas T-cell responses to phytohemagglutinin are insensitive to KBA MAb. The inhibitory effect of KBA MAb is observed only when KBA MAb is added to the culture at an early time. This indicates that the lymphokine-activated cell-associated antigen (LAA) defined by KBA MAb plays an important role in the early stages of T-cell activation. Con A-induced interleukin 2 (IL-2) receptor acquisition and IL-2 production, both of which are required for the early steps of T-cell activation, were greatly inhibited by KBA MAb. However, KBA MAb did not inhibit the action of IL-2, which is required for later stages of T-cell activation.