Human Cell Surface Antigens Research Articles

Tyrosine Phosphorylation of the c-cbl Proto-oncogene Product Mediated by Cell Surface Antigen CD38 in HL-60 Cells

The human cell surface antigen CD38 is a 46-kDa type II transmembrane glycoprotein with a short N-terminal cytoplasmic domain and a long Cys-rich C-terminal extracellular one. We demonstrated previously that the extracellular domain of CD38 has NAD+ glycohydrolase (NADase) activity and that the ecto-form NADase activity induced in HL-60 cells during cell differentiation by retinoic acid is due to CD38. In the present study, we investigated the intracellular signaling mediated by CD38 in retinoic acid-differentiated HL-60 cells with an anti-CD38 monoclonal antibody. The addition of anti-CD38 monoclonal antibody to the cells induced rapid tyrosine phosphorylation of the cellular proteins with molecular weights of 120,000, 87,000, and 77,000. An increase in tyrosine kinase activity in the anti-phosphotyrosine immunoprecipitates of the cells was also observed after the addition of anti-CD38 monoclonal antibody. Moreover, one of the prominent tyrosine-phosphorylated proteins stimulated by the anti-CD38 monoclonal antibody was identified as the c-cbl proto-oncogene product, p120c-cbl. These results indicated that tyrosine phosphorylation of cellular proteins, including p120c-cbl, is possibly involved in transmembrane signaling mediated by CD38.

Selection of transduced CD34+ progenitors and enzymatic correction of cells from Gaucher patients, with bicistronic vectors.

The gene transfer efficiency of human hematopoietic stem cells is still inadequate for efficient gene therapy of most disorders. To overcome this problem, a selectable retroviral vector system for gene therapy has been developed for gene therapy of Gaucher disease. We constructed a bicistronic retroviral vector containing the human glucocerebrosidase (GC) cDNA and the human small cell surface antigen CD24 (243 bp). Expression of both cDNAs was controlled by the long terminal repeat enhancer/promoter of the Molony murine leukemia virus. The CD24 selectable marker was placed downstream of the GC cDNA and its translation was enhanced by inclusion of the long 5' untranslated region of encephalomyocarditis virus internal ribosomal entry site. Virus-producing GP+envAM12 cells were created by multiple supernatant transductions to create vector producer cells. The vector LGEC has a high titer and can drive expression of GC and the cell surface antigen CD24 simultaneously in transduced NIH 3T3 cells and Gaucher skin fibroblasts. These transduced cells have been successfully separated from untransduced cells by fluorescence-activated cell sorting, based on cell surface expression of CD24. Transduced and sorted NIH 3T3 cells showed higher GC enzyme activity than the unsorted population, demonstrating coordinated expression of both genes. Fibroblasts from Gaucher patients were transduced and sorted for CD24 expression, and GC enzyme activity was measured. The transduced sorted Gaucher fibroblasts had a marked increase in enzyme activity (149%) compared with virgin Gaucher fibroblasts (17% of normal GC enzyme activity). Efficient transduction of CD34+ hematopoietic progenitors (20-40%) was accomplished and fluorescence-activated cell sorted CD24(+)-expressing progenitors generated colonies, all of which (100%) were vector positive. The sorted, CD24-expressing progenitors generated erythroid burst-forming units, colony-forming units (CFU)-granulocyte, CFU-macrophage, CFU-granulocyte/macrophage, and CFU-mix hematopoietic colonies, demonstrating their ability to differentiate into these myeloid lineages in vitro. The transduced, sorted progenitors raised the GC enzyme levels in their progeny cells manyfold compared with untransduced CD34+ progenitors. Collectively, this demonstrates the development of high titer, selectable bicistronic vectors that allow isolation of transduced hematopoietic progenitors and cells that have been metabolically corrected.

Generation and characterization of monoclonal antibodies specific to surface antigens of human trophoblast cells.

To generate and utilize specific monoclonal antibodies for routine fetal cell isolation from the maternal circulation. Monoclonal antibodies specific to human trophoblast cell surface antigens were generated and characterized. After cell fusion, antibodies secreted by hybridomas were screened by enzyme-linked immunosorbent assay and immunohistochemical assays. By using cultured BeWo choriocarcinoma cells or the membrane fraction of human placenta as the immunogen, seven (BW-108, 110, 123, 124, HP-15, 16 and 17) antibodies specific to the surface antigens of trophoblast were produced. They were shown to have little cross-reactivity to other human tissues. Among the antibodies raised against human sperm, HSA-10 was also found to cross-react with human trophoblast, but not detected in other tissues. When immobilized to magnetic beads, these antibodies were shown to react only with BeWo cells in suspension, but not blood cells and ovarian carcinoma cell line, OC-3-VGH. Therefore, these antibodies may have potential application in fetal trophoblast cell isolation from the maternal circulation for prenatal genetic diagnosis.

The Severe Combined Immunodeficient-Human Peripheral Blood Stem Cell (SCID-huPBSC) Mouse: A Xenotransplant Model for huPBSC-Initiated Hematopoiesis

Mononuclear cells (MNCs) containing peripheral blood stem cells (PBSCs) were obtained from solid-tumor patients undergoing mobilizing chemotherapy followed by granulocyte colony-stimulating factor for PBSC transplantation-supported dose-intensified anticancer chemotherapy and were transplanted into unconditioned "nonleaky" young severe combined immunodeficient mice. Multilineage engraftment was shown by flow cytometry and immunocytochemistry using monoclonal antibodies to various human cell surface antigens as well as identification of human immunoglobulin in murine sera. Within a dose range of MNCs suitable for transplantation (10 to 36 x 10(6) cells/graft) the number of CD34+ cells injected (optimal at > 0.7 x 10(6)/graft) determined the yield of human cells produced in recipient animals. Engraftment of hu PBSC preparations resulted in prolonged generation of physiologic levels of human cytokines including interleukin-3 (IL-3), IL-6, and granulocyte-macrophage colony-stimulating factor, which were detectable in the murine blood over a period of at least 4 months. In vivo survival of immature human progenitor cells was preserved even 9 months after transplantation. Because human IL-3 is known to stimulate early hematopoiesis, a rat fibroblast cell line was stably transfected with a retroviral vector carrying the human IL-3 gene and cotransplanted subcutaneously as additional source of growth factor. Cotransplants of this cell line producing sustained in vivo levels of circulating human IL-3 for at least 12 weeks significantly accelerated the process of engraftment of huPBSC and spurred the spread of mature human cells to the murine spleen, liver, thymus, and peripheral blood. Cotransplants of allogeneic human bone marrow stromal cells derived from long-term cultures resulted in a comparable--though less prominent--support of engraftment.

Characterization of human thymic epithelial cell surface antigens: Phenotypic similarity of thymic epithelial cells to epidermal keratinocytes

Cellular interactions between developing thymocytes and cells of the thymic microenvironment are necessary for maturation of thymocytes into mature T cells. While much is known about the molecules on developing T cells that mediate these interactions, little is known about the surface molecules of human thymic epithelial (TE) cells. In this study, using a panel of 276 MAb including 255 MAb from the 5th International Workshop on Human Leukocyte Differentiation Antigens (HLDA-V), we have determined the expression of CD1 through CDw130 and other surface molecules on resting and IFN-gamma-activated cultured human TE cells and on resting epidermal keratinocytes (EK). We demonstrate the surface expression of 50 of the 161 molecules assayed for on TE cells, including a number of adhesion molecules, cytokine receptors, Apo-1, and MHC-encoded molecules. While activation of TE cells with IFN-gamma for 48 hr induced a greater than fivefold increase in the expression of four surface molecules (CD38, CD54, MHC class I, and MHC class II), it also induced a greater than 50% increase in the expression of 14 other surface molecules (CD12, CD29, CD40, CD44, CD47, CD49b, CD49c, CD49e, CD55, CD66, CD87, CD104, TE4, and STE3) and a decrease in the expression of three molecules (CDw65, CDw109, and STE2). In comparing the phenotype of TE cells to 83 other cell lines studied in HLDA-V, we found that TE cells were strikingly more similar to EK than to any of the other cell types tested.

Involvement of pertussis toxin-sensitive mechanism in retinoic acid-induced differentiation of human leukemic HL-60 cells.

Retinoic acid-induced differentiation of human leukemic HL-60 cells is accompanied with the early induction of an ecto-enzyme of NAD+ glycohydrolase (NADase), which has recently been identified as human leukocyte cell surface antigen CD38 [Kontani, K. et al. (1993) J. Biol. Chem. 268, 16895-16898]. The terminal cell differentiation attendant upon the cell growth arrest was, but the early induction of CD38 NADase activity was not, inhibited by prior treatment of HL-60 cells with pertussis toxin, which catalyzed ADP-ribosylation of the membrane-bound alpha beta gamma-trimeric GTP-binding proteins. The prior treatment was, however, not essential for the toxin-induced inhibition of the cell differentiation; the inhibition by the addition of pertussis toxin was still observed even after retinoic acid-induced expression of CD38 antigen. This suggested that a pertussis toxin-sensitive mechanism was involved in a late process of cell differentiation. Indeed, HL-60 cells appeared to secrete a differentiation-supporting factor in response to retinoic acid, since the cell differentiation was accelerated and potentiated upon culture of the cells in a conditioned medium prepared from retinoic acid-treated cells. The action of the differentiation-supporting factor was destroyed by heating and markedly attenuated in pertussis toxin-pretreated HL-60 cells. Thus, the whole process of the retinoic acid-induced cell differentiation appeared to consist of two distinguishable periods in terms of sensitivity to pertussis toxin; the toxin-insensitive early period characterized by the induction of CD38 NADase activity and the toxin-sensitive late period in which the secretion of a differentiation-supporting factor might be involved.

シグナル伝達におけるNAD代謝酵素とサイクリックADPリボース

The human cell surface antigen CD38 is a 46-kDa type II transmembrane glycoprotein with a short N-terminal cytoplamic domain and a long Cys-rich C-terminal extracellular one. Although CD38 and Aplysia ADP-ribosyl cyclase exhibit amino acid-sequence homology and both catalyze the formation of nicotinamide from β-NAD+, the other reaction products of the two enzymes are different; ADP-ribose and cyclic ADP-ribose being predominantly generated by CD38 and Aplysia cyclase, respectively. To identify the structural determinant responsible for the different reaction products, we synthesized a series of chimeric proteins between the two enzymes in COS-7 cells. Our results indicated that a limited sequence near the carboxyl terminus of CD38 plays an important role not only in the enzyme activity but also in determination of the enzyme type categorized as a hydrolase. We also investigated the intracellular signaling mediated through CD38 in HL-60 cells which had been caused to differentiate by retinoic acid (RA). Addition of an anti-CD38 monoclonal antibody (mAb) to the cells induced a rapid tyrosine phosphorylation of the cellular proteins with the molecular weights of 120, 000, 87, 000 and 77, 000. Tyrosine kinase activity in the cell lysate immunoprecipitated with anti-phosphotyrosine mAb was also stimulated after the addition of the anti-CD38 mAb. Moreover, one of the prominent phosphorylated proteins stimulated by the anti-CD38 mAb was identified as the cbl proto-oncogene product, p120c-cbl. These results indicated that tyrosine phosphorylation of cellular proteins including pl20c-cbl is possibly involved in transmembrane signaling mediated through CD38.

Selection of retrovirally transduced hematopoietic cells using CD24 as a marker of gene transfer

We have investigated the use of a cell surface antigen as a dominant selectable marker to facilitate the detection and selection of retrovirally infected target cells. The small coding region of the human cell surface antigen CD24 (approximately 240 bp) was introduced into a myeloproliferative sarcoma virus (MPSV)-based retroviral vector, which was then used to infect day 4 5-fluorouracil (5-FU)-treated murine bone marrow cells. Within 48 hours of termination of the infection procedure CD24-expressing cells were selected by fluorescent- activated cell sorting (FACS) with an antibody directed against the CD24 antigen. Functional analysis of these cells showed that they included not only in vitro clonogenic progenitors and day 12 colony- forming unit-spleen but also cells capable of competitive long-term hematopoietic repopulation. Double-antibody labeling studies performed on recipients of retrovirally transduced marrow cells showed that some granulocytes, macrophages, erythrocytes, and, to a lesser extent, B and T lymphocytes still expressed the transduced CD24 gene at high levels 4 months later. No gross abnormalities in hematopoiesis were detected in mice repopulated with CD24-expressing cells. Our results show that the use of the CD24 cell surface antigen as a retrovirally encoded marker enables the rapid, efficient, and nontoxic selection in vitro of infected primary cells, facilitates tracking and phenotyping of their progeny, and should provide a unique tool to identify elements that regulate the expression of transduced genes in the most primitive hematopoietic cells.

Selection of Retrovirally Transduced Hematopoietic Cells Using CD24 as a Marker of Gene Transfer

We have investigated the use of a cell surface antigen as a dominant selectable marker to facilitate the detection and selection of retrovirally infected target cells. The small coding region of the human cell surface antigen CD24 (approximately 240 bp) was introduced into a myeloproliferative sarcoma virus (MPSV)-based retroviral vector, which was then used to infect day 4 5-fluorouracil (5-FU)-treated murine bone marrow cells. Within 48 hours of termination of the infection procedure CD24-expressing cells were selected by fluorescent-activated cell sorting (FACS) with an antibody directed against the CD24 antigen. Functional analysis of these cells showed that they included not only in vitro clonogenic progenitors and day 12 colony-forming unit-spleen but also cells capable of competitive long-term hematopoietic repopulation. Double-antibody labeling studies performed on recipients of retrovirally transduced marrow cells showed that some granulocytes, macrophages, erythrocytes, and, to a lesser extent, B and T lymphocytes still expressed the transduced CD24 gene at high levels 4 months later. No gross abnormalities in hematopoiesis were detected in mice repopulated with CD24-expressing cells. Our results show that the use of the CD24 cell surface antigen as a retrovirally encoded marker enables the rapid, efficient, and nontoxic selection in vitro of infected primary cells, facilitates tracking and phenotyping of their progeny, and should provide a unique tool to identify elements that regulate the expression of transduced genes in the most primitive hematopoietic cells.

Identification of a human OX-40 ligand, a costimulator of CD4+ T cells with homology to tumor necrosis factor.

The human OX-40 cell surface antigen is a CD4+ T cell activation marker that acts as a costimulatory receptor and is a member of the nerve growth factor receptor/tumor necrosis factor (TNF) receptor family. Using a soluble form of the receptor, the extracellular region fused with human immunoglobulin Fc, we expression cloned the human OX-40 ligand cDNA from a library derived from an activated B lymphoblastoid cell line MSAB. The encoded protein is identified as gp34, a type II transmembrane antigen previously known to be expressed only by human T cell lymphotropic virus 1-infected cells. We describe gp34 as a new member of the TNF family, and find that the recombinant ligand expressed in COS cells costimulates phorbol myristate acetate, phytohemagglutinin, and anti-CD3-induced CD4+ T cell proliferation.

Mapping of CD24 and Homologous Sequences to Multiple Chromosomal Loci

The human cell surface antigen, CD24, is a glycosyl phosphatidylinositol (GPI)-linked glycoprotein that has been implicated in the differentiation and activation of granulocytes and B lymphocytes. Changes in expression of the antigen occur at critical times during B lineage development. CD24 was cloned by its homology to mouse heat-stable antigen. Southern blot analysis suggested the presence of multiple CD24 related sequences in the human genome. We have now mapped CD24 homologous sequences to chromosomes 6q21, 15q21-q22, and Yq11 by screening a panel of somatic cell hybrid DNAs and by in situ hybridization. At least two additional homologues, one located on chromosome 1 at band p36 and one tentatively mapped to chromosome 20, that are distantly related to CD24 were identified. Southern analysis of male and female DNA samples confirmed the presence of CD24 homologous sequences on the human Y chromosome. Sequencing of DNA fragments amplified from monochromosomal somatic cell hybrids showed that the CD24 cDNA was derived from a transcript originating from a gene on chromosome 6. The CD24 gene on the Y chromosome had many base changes compared to the cDNA but had retained an open reading frame, leaving open the question of whether this gene is functional. Both ATGs in the translation initiation region of CD24 homologous sequences on chromosome 15 were converted to GTGs, making it unlikely that this gene, if functional, encodes a protein similar to CD24. CD24, therefore, is a member of a multigene family, but it remains to be determined whether any of the related genes are functional.

Human monoclonal antibody developed against ovarian cancer cell surface antigen

Murine monoclonal antibodies (MoAb) potentially can be used in the radioimmunodetection and radioimmunotherapy of cancer. However, the administration of these radiopharmaceuticals to humans often leads to induction of human anti-murine antibodies (HAMA). HAMA has many disadvantages, which could decrease efficacy of the murine MoAb. The purpose of this work was to produce human monoclonal antibody against a human ovarian cancer cell surface antigen (OCCSA), which was not present in normal ovarian cells. This 200-kilodalton OCCSA also was used in the present study for characterizing the human monoclonal antibody. Human monoclonal antibodies were produced in vitro by fusion of mutant myeloma cells, selected from GM1500, with human lymphoid cells immunized in vitro with purified OCCSA: The human monoclonal antibody was characterized using the following techniques: sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), native-PAGE, Western blotting followed by protein-A gold staining, immunodiffusion assays, and fluorescent antibody assays. Human monoclonal antibody, TC5 (immunoglobulin G1), was produced and purified. It was found to be specific for ovarian cancer, while also reacting with an early stage breast cancer. TC5 did not react with any normal (i.e., nonneoplastic) cells of the ovary, uterus, cervix, endocervix, or fallopian tube, nor did it react with normal lung, heart, pancreas, liver, or breast tissue. Human-human hybridomas produced human monoclonal antibody against OCCSA: The human monoclonal antibody, TC5, was specific for ovarian and breast cancer. TC5 did not react with any normal tissue tested. Future work will focus on the in vivo characterization of the human monoclonal antibody, after labeling with radionuclides.

Genetic infection induces protective in vivo immune responses.

Drug-induced abortive retroviral infection has been reported to induce both T-cell and B-cell immunity in vivo. We sought to analyze if replication-incompetent retroviruses could induce the development of similarly protective in vivo immune responses in a more desirable fashion. To evaluate retroviral transduction vaccination (genetic infection), a plasmid encoding human CD4 in a retroviral vector was transfected into the pA317 amphotropic retroviral packaging system. The resulting replication defective retrovirus was used to transduce BALB/c mice prior to tumor challenge with human CD4. Immunization elicited specific humoral and cellular anti-human CD4 responses. We evaluated anti-cell responses using a tumor model system. We observed that BALB/c mice challenged with SP2/0 lymphoma cells develop lethal tumors and die within 7 weeks of challenge. Cloned SP2/0 cells stably transfected with the human cell-surface antigen CD4 also develop tumors in naive mice and succumb to the tumors in a similar manner to SP2/0 inoculated animals. In contrast, CD4 retrovirus-transduced animals, when challenged with the CD4-expressing SP2/0 cells, demonstrated a low incidence of tumors and significantly enhanced survival compared to the mice immunized similarly with human CD8 retrovirus. These results establish an in vivo tumor challenge system with relevance to the development of protective in vivo immune responses, and indicate that genetic infection is a useful technique for inducing protective immunity.

Efficient immunostaining of tissue sections with chemically modified monoclonal antibody

Monoclonal antibodies (mAbs) were modified with a photo-cross linker, sulfosuccinimidyl 2-( m-azido- o-nitrobenzamido)-ethyl 1,3'- dithiopropionate (SAND), and their efficacy in immunohistochemical staining of tissue sections was examined comparatively with that of unmodified mAbs. mAbs used were HBJ127 and SV2-61γ which recognized a proliferation-associated human gp125 cell surface antigen and a human c- erbB-2 protooncogene product, respectively. Both mAbs could stain relevant cancer tissue in frozen sections but not that in paraffin sections. Whereas SAND-modified mAbs intensely stained the cancer tissue in paraffin sections too, and the UV irradiation to SAND-modified mAb-treated tissue sections further increased the intensity of the staining. Scatchard plot analysis using 125I-labeled mAbs indicated that the augmentation of staining capacity by the SAND modification is due to the increase of the mAb amount capable of binding to the antigen.

NAD glycohydrolase specifically induced by retinoic acid in human leukemic HL-60 cells. Identification of the NAD glycohydrolase as leukocyte cell surface antigen CD38

Human leukemic HL-60 cells are differentiated into granulocytic cells by retinoic acid, and this differentiation is preceded by the induction of an ecto-enzyme of NAD glycohydrolase (NADase). The NADase specifically induced by retinoic acid appeared to be encoded by human leukocyte cell surface antigen CD38 as follows. 1) There was an early expression of CD38 mRNA, together with the induction of the NADase activity, in the retinoic acid-treated HL-60 cells. 2) The time course of the expression of CD38 antigen on the cell surface was well correlated with that of the induction of NADase activity. 3) The NADase activity solubilized from the differentiated HL-60 cell membrane could be immunoprecipitated with an anti-CD38 monoclonal antibody. 4) Introduction of the CD38 cDNA into Escherichia coli cells resulted in the expression of an NADase, the activity of which was inhibited by dithiothreitol. The NADase activity in the differentiated cells was also inhibited by the reducing reagent. These results clearly indicated that the dithiothreitol-sensitive NADase activity induced by retinoic acid in HL-60 cells is attributed to the molecule of human leukocyte cell surface antigen CD38, which contains cysteine-rich cytoplasmic domain within its molecule.

UN-1, a murine monoclonal antibody recognizing a human thymocyte undescribed antigen

A monoclonal antibody (MoAb), UN-1, specific for a human thymocyte cell surface antigen was produced. The same MoAb recognized in immunofluorescence also cells of the human T line HPB-ALL, while did not bind human peripheral blood cells and cells of some T, B and myeloid lines. Western blotting analysis of thymocyte membranes with MoAb UN-1 revealed a structure with a molecular weight of 150 kDa. Therefore both the pattern of expression and the size of the antigen recognized by MoAb UN-1 did not correspond to any previously described cell surface molecule.

Generation of monoclonal antibodies to human lymphocyte cell surface antigens using insect cell expressing recombinant proteins

We have expressed human CD40 and human B7 in insect cells using the baculovirus expression system and have used these insect cells to immunize mice for the generation of monoclonal antibodies. We demonstrate here that specific monoclonal antibodies to human CD40 and human B7 were obtained using this approach. One significant advantage of this method is that immunizing mice with insect cells did not evoke an immune response to human cells and, therefore, EBV-transformed human B cells could be used to screen for specific antibody production by the hybridoma clones.

Immunotherapy with monoclonal antibodies in metastatic melanoma.

Therapy for metastatic melanoma has been disappointing to date. Treatment with chemotherapy only uncommonly results in complete responses and rarely results in long-term survivors. The identification of human melanoma cell surface antigens has led to the development of an array of mouse monoclonal antibodies (MAb) for use in the diagnosis and therapy of patients with metastatic melanoma. Strategies utilizing MAbs based on immunologic approaches have been developed. Naked MAbs directed against glycoprotein surface antigens or conjugated to toxins or radionuclides have shown little biologic or clinical activity. However, phase I studies of MAb directed against glycolipid antigens have yielded objective tumor shrinkage with occasional complete responses. Severe toxicity has been seen infrequently. Possible anti-tumor mechanisms include complement activation and antibody-dependent cellular cytotoxicity utilizing natural killer cells or monocytes as effector cells. Strategies to enhance the anti-tumor effects of MAb, including combinations with cytotoxic agents and cytokines, have been introduced with limited success thus far. The development of a human IgG anti-mouse antibody has been seen in nearly all treated patients. A new generation of MAb engineered to overcome the immunogenicity of mouse MAb and to enhance immune effector function will soon enter clinical trials.

Heterogeneity of peripheral blood reticulocytes: A flow cytometric analysis with monoclonal antibody HAE9 and thiazole orange

The expression of a human erythroid cell surface antigen recognized by monoclonal antibody (mAB) HAE9 has been studied on peripheral blood reticulocytes by one- and two-color flow cytometry. Total reticulocyte count was determined using Thiazole Orange (TO) and flow cytometry. In normal individuals, 4.56% of reticulocytes were stained by FITC-labeled mAB HAE9. The correlation between reticulocyte percentage by TO and HAE9 staining was 0.828 (P less than 0.0001) in patients with hematocrits less than 0.25. A HAE9-positive reticulocyte percentage of 6-44% was observed when analyzed by two-color flow cytometry with TO and mAB HAE9. These findings, in conjunction with previous studies, suggest that mAB HAE9 recognizes an early, less differentiated population of peripheral blood reticulocytes. Enumeration of immature reticulocytes may be of clinical utility.

Human cell surface antigen Fas which mediates apoptosis: Molecular cloning and preparation of monoclonal antibodies: [formula omitted]. The Tokyo Metro.Inst.Med.Sci., Tokyo 113, Japan, and Osaka Biosci.Inst., Osaka 565, Japan

Human cell surface antigen Fas which mediates apoptosis: Molecular cloning and preparation of monoclonal antibodies: [formula omitted]. The Tokyo Metro.Inst.Med.Sci., Tokyo 113, Japan, and Osaka Biosci.Inst., Osaka 565, Japan