Showing papers on "Cell culture published in 1980"
TL;DR: These preparations should significantly aid in efforts to examine the biochemistry, physiology, and pharmacology of these two major classes of central nervous system cells.
Abstract: A novel method has been developed for the preparation of nearly pure separate cultures of astrocytes and oligodendrocytes. The method is based on (a) the absence of viable neurons in cultures prepared from postnatal rat cerebra, (b) the stratification of astrocytes and oligodendrocytes in culture, and (c) the selective detachment of the overlying oligodendrocytes when exposed to sheer forces generated by shaking the cultures on an orbital shaker for 15--18 h at 37 degrees C. Preparations appear greater than 98% pure and contain approximately 1-2 x 10(7) viable cells (20--40 mg of cell protein). Three methods were used to characterize these two culture t ypes. First, electron microscopic examination was used to identify the cells in each preparation (mixed and separated cultures of astrocytes and oligodendrocytes) and to assess the purity of each preparation. Second, two oligodendroglial cell markers, 2',3'-cyclic nucleotide 3'-phosphohydrolase (EC 3.1.4.37) and glycerol phosphate dehydrogenase (EC 1.1.1.8) were monitored. Third, the regulation of cyclic AMP accumulation in each culture type was examined. In addition to these studies, we examined the influence of brain extract and dibutyryl cAMP on the gross morphology and ultrastructure of each preparation. These agents induced astroglial process formation without any apparent morphological effect on oligodendrocytes. Collectively, the results indicate that essentially pure cultures of astrocytes and of oligodendrocytes can be prepared and maintained. These preparations should significantly aid in efforts to examine the biochemistry, physiology, and pharmacology of these two major classes of central nervous system cells.
3,785 citations
TL;DR: Results indicate that THP‐1 is a leukemic cell line with distinct monocytic markers, and the ability to restore T‐lymphocyte response to Con A.
Abstract: A human leukemic cell line (THP-1) cultured from the blood of a boy with acute monocytic leukemia is described. This cell line had Fc and C3b receptors, but no surface or cytoplasmic immunoglobulins. HLA haplotypes of THP-1 were HLA-A2, -A9, -B5, -DRW1 and -DRW2. The monocytic nature of the cell line was characterized by: (1) the presence of alpha-naphthyl butyrate esterase activities which could be inhibited by NaF; (2) lysozyme production; (3) the phagocytosis of latex particles and sensitized sheep erythrocytes; and (4) the ability to restore T-lymphocyte response to Con A. The cells did not possess Epstein-Barr virus-associated nuclear antigen. These results indicate that THP-1 is a leukemia cell line with distinct monocytic markers. During culture, THP-1 maintained these monocytic characteristics for over 14 months.
2,209 citations
TL;DR: Analysis of the cell culture fluid from two new human hepatoma-derived cell lines reveals that 17 of the major human plasma proteins are synthesized and secreted by these cells.
Abstract: Analysis of the cell culture fluid from two new human hepatoma-derived cell lines reveals that 17 of the major human plasma proteins are synthesized and secreted by these cells. One of these cell lines, Hep 3B, also produces the two major polypeptides of the hepatitis B virus surface antigen. When Hep 3B in injected into athymic mice, metastatic hepatocellular carcinomas appear. These cell lines provide experimental models for investigation of plasma protein biosynthesis and the relation of the hepatitis B viru genome to tumorigenicity.
1,918 citations
TL;DR: It is shown that maintenance in vitro of these specialized functions of rat thyroid follicular cells is dependent on low serum concentrations and supplementation with hormones in the primary cultures and may be aplicable to the general problem of maintenance of differentiated characteristics in cultures of other epithelial cells.
Abstract: Primary cultures of rat thyroid cells were made in medium supplemented with 0.1--0.5% calf serum and containing six hormones or growth factors: insulin, thyrotropin, transferrin, hydrocortisone, somatostatin, and glycyl-L-histidyl-L-lysine acetate. The FRTL strain was purified by successive colonial isolations and was found to maintain highly differentiated features (secretion into the culture medium of physiological amounts of thyroglobulin and concentration of iodide by 100-fold). The FRTL strain has been observed for more than 3 years in continuous culture. It has maintained the same biochemical and morphological characteristics that typified the primary cultures of thyroid follicular cells immediately after their enzymatic release from the rat thyroid. Thyroid epithelial cells that were grown under more conventional cell culture conditions failed to retain these specialized characteristics. We show that maintenance in vitro of these specialized functions of rat thyroid follicular cells is dependent on low serum concentrations and supplementation with hormones in the primary cultures. Our observations indicate that this culture strategem may be aplicable to the general problem of maintenance of differentiated characteristics in cultures of other epithelial cells.
947 citations
932 citations
TL;DR: It is suggested that the cell lines represent a self-renewing population of cells ancestral to GM colony- forming cells, which may be responding to a hitherto unrecognized regulator.
Abstract: Cell lines have been produced from long-term cultures of mouse bone marrow that require a factor, present in WEHI-3 conditioned medium (CM) or in spleen CM, for their sustained growth. The cell lines were obtained from nonvirus-treated cultures, are nonleukemic, maintain a normal karyotype, and form colonies showing granulocyte maturation when plated in soft agar. Granulocyte/macrophage (GM) colony-stimulating factor is not the inductive moiety involved in the maintenance of proliferation of these cells. It is suggested that the cell lines represent a self-renewing population of cells ancestral to GM colony-forming cells, which may be responding to a hitherto unrecognized regulator.
724 citations
TL;DR: The present results suggest that postnatal marrow contains osteogenic precursors with the potential to differentiate via either of the two major paths followed during skeletal development in the embryo.
Abstract: When freshly isolated rabbit marrow cells were cultured either in vitro or in diffusion chambers in vivo, the hemopoietic cells disappeared and there was a proliferation of the stromal cell population. The colonies formed in vitro were mainly fibroblastic, and this cell type predominated in confluent cultures. Staining for alkaline phosphatase activity and for the Von Kossa reaction was negative in in vitro cultures. However, marrow cell suspensions or fibroblasts harvested from in vitro culture of marrow cells, gave rise to a mixture of bone, cartilage and fibrous tissue in diffusion chambers implanted into the peritoneal cavity. In contrast, only a soft fibrous tissue developed from spleen fibroblasts in diffusion chambers. Differentiation of osteogenic tissue within diffusion chambers fell into two categories: (1) Formation of bone in a fibrous layer surrounding cartilage; (2) intramembranous bone formed directly within fibrous tissue unassociated with cartilage. In both cases alkaline phosphatase activity appeared before the onset of mineralization, and decreased as the first signs of mineral became apparent. The present results suggest that postnatal marrow contains osteogenic precursors with the potential to differentiate via either of the two major paths followed during skeletal development in the embryo. Clonal analysis of the marrow stromal cell population will be required to clarify whether osteo-, chondro-, and fibrogenic cells are the products of one stromal cell line modulated by the microenvironment, or whether there are distinct cell lines for each type.
622 citations
TL;DR: Two cell lines have been isolated from testis of immature BALB/c mice and are tentatively identified as being of Sertoli cell origin, since it shows a growth response to purified ovFSH and an increase in cAMP in the presence of FSII but not LII.
Abstract: Two cell lines have been isolated from testis of immature BALB/c mice. These lines have each been cloned several times and have been established in culture for over 2 years. The cells are epithelial in appearance and do not form tumors when injected into BALB/c - nu/nu mice. l’hc cell lines can be said to be two distinct cell types on the basis of their morphology, hormone response, responses to gonadotropins, and metabolism of steroids. One line (TM4) has been tentatively identified as being of Sertoli cell origin, since it shows a growth response to purified ovFSH and an increase in cAMP in the presence of FSII but not LII. The other line (TM3), believed to be Leydig cells, is not growth-stimulated by either LII or FSII, shows an increase in cAMP in the presence of LII, and a change in the metabolism of Itm4 Cl cholesterol in the presence of LI-I.
620 citations
TL;DR: The rate of total cellular protein synthesis also increases early early in differentiation, lending support to a model in which the synthesis of a large number of "differentiated proteins" is coordinately induced.
574 citations
TL;DR: Six distinct antigenic systems were defined by direct serological assays and absorption tests with a panel of 41 cell lines derived from normal and malignant human tissues, finding each has a distinctive pattern of distribution on various cell types, varying from a broad representation to a more restricted occurrence.
Abstract: Eighteen mouse monoclonal antibodies were selected for reactivity with cell surface antigens of the immunizing human melanoma cell line SK-MEL-28. Six distinct antigenic systems were defined by direct serological assays and absorption tests with a panel of 41 cell lines derived from normal and malignant human tissues. Biochemical analysis indicated that two of the antigens are glycoproteins with molecular sizes of 95,000 and 150,000 daltons (gp95 and gp150). Two other antigenic systems (O5 and the R24 group) are associated with heat-stable molecules having the characteristics of glycolipids. The remaining two antigens (M19 and R8) are heat labile, but molecular characterization has not been possible. Each of the antigenic systems has a distinctive pattern of distribution on various cell types, varying from a broad representation to a more restricted occurrence. O5 appears to be a species antigen, being present on virtually every human cell type tested. gp95, gp150, M19, and R8 are found on a characteristic proportion of melanomas, astrocytomas, and epithelial cancers and on normal kidney cells. The antigen defined by the R24 antibody has the most restricted distribution of all. Reactivity is found with melanomas and astrocytomas, whereas epithelial cell types, fibroblasts, and cells of hematopoietic origin lack R24. Although occurrence of gp95, gp150, M19, and R8 distinguishes a small subset of melanomas not expressing these antigens, R24 is found on all melanoma cells.
547 citations
TL;DR: Continuous cell lines that secrete both insulin and somatostatin were established by two cooperating groups of investiagtors from a serially transplantable, radiation-induced, rat islet cell tumor and provide important systems to study the biology of insulin and Somatostarin.
Abstract: Continuous cell lines that secrete both insulin and somatostatin were established by two cooperating groups of investiagtors from a serially transplantable, radiation-induced, rat islet cell tumor. The cell lines, named RIN-r and RIN-m, were initiated from tumors maintained in inbred rats or in athymic nude mice, respectively. The cultured cells are epithelioid, free of fibroblast contamination, and can be cloned. They have a hypodiploid chromosome number, are tumorigenic, and posses amine-handling properties, including high levels of L-dopa decarboxylase and formaldehyde-induced fluorescence. Preliminary analysis of clones revealed a spectrum of insulin secretion from undetectable to relatively high. These clonal cell lines provide important systems to study the biology of insulin and somatostatin.
TL;DR: The properties of these intracellular polypeptides from both virally and chemically transformed cells are similar to those described for the Sarcoma growth factors previously isolated from the conditioned medium of sarcoma virus-transformed mouse 3T3 cells, suggesting the definition of a class of transforming growth factors common to tumor cells of different origins.
Abstract: Polypeptides characterized by their ability to confer a transformed phenotype on an untransformed indicator cell have been isolated directly from tumor cells growing both in culture and in the animal, by using an acid/ethanol extraction procedure. Assay of these polypeptides is based on their ability to induce normal rat kidney fibroblasts to form colonies in soft agar. Peptides from murine sarcoma virus-transformed mouse 3T3 cells grown in culture had the highest specific activity in this assay; peptides from sarcomas produced from these cells or from chemically induced transplantable bladder carcinomas of mice were one-third as active; and peptides from a chemically induced rat tracheal carcinoma had only one-tenth the activity. Treatment with either trypsin or dithiothreitol destroyed the activity of all of these materials. The properties of these intracellular polypeptides from both virally and chemically transformed cells are similar to those described for the sarcoma growth factors (SGFs) previously isolated from the conditioned medium of sarcoma virus-transformed mouse 3T3 cells, suggesting the definition of a class of transforming growth factors common to tumor cells of different origins. The transforming peptides from the cultured sarcoma virus-infected cells were separately by gel filtration into two fractions of apparent molecular weight 7000 and 10,000. The major fraction at molecular weight 7000 represented approximately 0.1% of the original cell protein and had a specific activity 50 times that of the original acid/ethanol extract.
TL;DR: It is suggested that only Schwann cells which have been induced to myelinate make detectable amounts of galactocerebroside, sulfatide, myelin basic protein (BP), or the major peripheral myelin glycoprotein (P0).
Abstract: We have used antibodies to identify Schwann cells and oligodendrocytes and to study the expression of myelin-specific glycolipids and proteins in these cells isolated from perinatal rats. Our findings suggest that only Schwann cells which have been induced to myelinate make detectable amounts of galactocerebroside (GC), sulfatide, myelin basic protein (BP), or the major peripheral myelin glycoprotein (P0). When rat Schwann cells were cultured, they stopped making detectable amounts of these myelin molecules, even when the cells were associated with neurites in short-term explant cultures of dorsal root ganglion. In contrast, oligodendrocytes in dissociated cell cultures of neonatal optic nerve, corpus callosum, or cerebellum continued to make GC, sulfatide and BP for many weeks, even in the absence of neurons. These findings suggest that while rat Schwann cells require a continuing signal from appropriate axons to make detectable amounts of myelin-specific glycolipids and proteins, oligodendrocytes do not. Schwann cells and oligodendrocytes also displayed very different morphologies in vitro which appeared to reflect their known differences in myelinating properties in vivo. Since these characteristic morphologies are maintained when Schwann cells and oligodendrocytes were grown together in mixed cultures and in the absence of neurons, we concluded that they are intrinsic properties of these two different myelin-forming cells.
TL;DR: The liposome-mediated delivery of nucleic acids may have potential for increasing the efficiency of DNA delivery to cells and for extending the number of cell types which can be transformed or transfected.
TL;DR: The results indicate that the leftmost 4.5% of Ads DNA is able to convert diploid cells in a primary culture into established aneuploid cell lines which still lack several of the properties characteristic for adenovirus 5-transformed cells.
TL;DR: These studies identify a new source of human IL-2 and establish a valuable reagent for the isolation and further molecular characterization of this immunoregulatory molecule.
Abstract: To isolate a stable tumor cell line capable of producing human interleukin 2 (IL-2; formerly referred to as T cell growth factor), 16 human T and B leukemia cell lines were screened for constitutive and mitogen-stimulated IL-2 production. We found that the T cell leukemia line designated Jurkat-FHCRC produced > 200 U/ml of IL-2 activity after a 24-h stimulation with T cell mitogens. Peak mitogen-induced IL-2 activity was found in supernates harvested from 24-h Jurkat-FHCRC cell cultures stimulated with either 1% phytohemagglutinin or 20 microgram/ml concanavalin A. Addition of the fatty acid derivative phorbol myristate acetate to mitogen-stimulated cultures increased Jurkat-FHCRC IL-2 production to concentrations > 400 U/ml. IL-2 activity observed in such cases represented between 100--300 times that produced in conventional cultures of mitogen- or alloantigen-stimulated normal human peripheral blood or splenic lymphocytes. Jurkat-FHCRC-derived conditioned medium demonstrated equal capacity to promote the sustained in vitro proliferation of either murine or human activated T cell lines confirming the ability of Jurkat-FHCRC cells to produce human IL-2. These studies identify a new source of human IL-2 and establish a valuable reagent for the isolation and further molecular characterization of this immunoregulatory molecule.
TL;DR: The results suggest that the bulk of L-cystine or L-glutamate is transported into the human fibroblasts via a common carrier system.
TL;DR: Investigations with these cell lines, and selected variants, should provide important insights into the cell biology and perhaps therapy of human leukemia.
TL;DR: Using electron microscopic immunocytochemistry, the intracellular location of the src protein (p21) in cells transformed by the Harvey strain of Murine Sarcoma Virus is investigated, suggesting that the plasma membrane is a major site of action for transforming proteins.
TL;DR: In this article, the authors showed that macrophage-derived cytotoxins are identical with serum-derived tumor-necrotizing factor, which further implies that the macrophages are the cellular source of tumor necrosis.
Abstract: Macrophage-enriched peritoneal exudate cells from mice infected with Mycobacterium bovis BCG, macrophage-like tumor cells (PU 5-1.8), and peritoneal macrophages propagated in vitro with macrophage growth factor released tumoricidal activity into the culture medium within 2 to 3 h after stimulation with nanogram quantities of bacterial lipopolysaccharide. The cytotoxic activities from each of the macrophage culture supernatants eluted from diethylaminoethyl-Sephacel columns at a sodium chloride concentration of 200 mM exhibited a molecular weight of 50,000 to 60,000 as estimated by gel filtration, were stable at 56 degrees C for 30 min, and were active at a pH range of 6 to 10. A rabbit antiserum directed against serum-derived cytotoxic activity (tumor-necrotizing factor) from BCG-infected and lipopolysaccharide-challenged mice inhibited all of the cytotoxic activities generated in vitro. This suggests that the macrophage-derived cytotoxins are identical with serum-derived cytotoxic factor, which further implies that the macrophage is the cellular source of tumor-necrotizing factor.
TL;DR: Two new monoclonal antibodies that react with surface antigens of human lymphocytes are described that were identified on the framework region of a T-cell antigen and designated HuLyt-1 and 9.3.
Abstract: We describe here two new monoclonal antibodies that react with surface antigens of human lymphocytes. Antibody 7.2 identified a determinant on the framework region of the human Ia antigen. It was cytotoxic for all cultured B-cell lines, normal B cells, and monocytes. The antibody was not cytotoxic for normal T cells or for established T leukemic cell lines. In immune precipitation assays, the 7.2 antibody reacted with a bimolecular complex of two chains that resolved in polyacrylamide gels as polypeptides with molecular weights of 29000 and 34000 daltons. These precipitation results were analogous to those achieved with a rabbit antiserum prepared against human Ia antigens. Antibody 9.3 identified a determinant on the framework region of a T-cell antigen. It was cytotoxic for 50–80% of peripheral T cells and for 20–50% of thymocytes. It was not cytotoxic for cultured B-cell lines, normal B cells, or monocytes. In immune precipitation assays, the 9.3 antibody reacted with a single polypeptide with a molecular weight of 44000 daltons. Due to the expression of this antigen on a limited subpopulation of human T cells, we have designated the antigen HuLyt-1.
TL;DR: It is suggested that the human HL‐60 cells share common cellular target sites for the inducing action of polar planar compounds, hypoxanthine and actinomycin‐D with some murine leukemic cells.
Abstract: Various compounds active in promoting in vitro differentiation of certain murine leukemia cell lines (Friend erythroleukemia cells and mouse myeloid leukemia cells) were tested for their capacity to induce differentiation of HL-60 cells, a human promyelocytic leukemia cell line capable of terminally differentiating in vitro to functionally mature granulocytes. Polar planar compounds including hexamethylene bisacetamide (HMBA), certain purines (particularly hypoxanthine), and actinomycin-D induced morphological and functional (as assessed by the capacity to reduce NBT dye) differentiation of HL-60. In contrast, hemin, ouabain, prostaglandin E1, X-irradiation, dexamethasone and some other anti-leukemic chemotherapeutic agents induced little if any significant differentiation of HL-60 cells. These results, together with previous observations with murine leukemia cells, suggest that the human HL-60 cells share common cellular target sites for the inducing action of polar planar compounds, hypoxanthine and actinomycin-D with some murine leukemic cells. In contrast, hemin, ouabain and prostaglandin E1 may be specific for mouse erythroleukemia cells, while X-irradiation and chemotherapeutic agents induce differentiation of both types (erythroid and myeloid) of mouse leukemic cells, but have little effect on HL-60 cells.
Journal Article•
TL;DR: It is concluded that at least some non-small-cell lung cancers have a much less stringent growth factor requirement for establishment, have higher cloning efficiencies, and lack APUD cell properties.
Abstract: Small-cell carcinoma of the lung (SCCL) grows rapidly in patients and can be maintained in culture for months but is difficult to establish in continuously replicating, clonable cell lines. We have established 15 SCCL cell lines from 11 patients. The SCCL lines grew as floating-cell aggregates with relatively long doubling times and formed tumors having typical SCCL histology in athymic nude mice. They had human enzyme markers, were aneuploid, and cloned in soft agarose at low efficiencies. These lines and their clonal derivatives expressed features of amine precursor uptake and decarboxylation (APUD) cells, including high dopa decarboxylase activity (EC 4.1.1.28), formaldehyde-induced fluorescence, and neurosecretory granules. While only two of 21 tumor specimens plated in fetal bovine serum-supplemented medium (growth medium) developed into continuous lines, 6 of 11 tumor specimens plated into growth medium conditioned by other SCCL cultures developed into lines. Conditioned medium also increased the colony-forming efficiency and colony size of some primary tumor specimens and early unestablished cultures, including one of the two specimens not absolutely requiring conditioned medium for initial growth. Continuous cell lines were eventually established from all eight SCCL tumors heterotransplanted in athymic nude mice; however, their replication was initially dependent on the presence of mouse stromal cell for periods of 3 to 24 months. Growth factor requirements of lung tumors of other histologies appeared less stringent; three of five non-SCCL lung tumors were readily established as continuous cell lines in growth medium. These cell lines from non-SCCL lung cancers lacked the APUD properties and neurosecretory granules characteristic of SCCL. We conclude that (a) human small-cell lung cancer lines and their clonal derivatives grown in vitro for long periods of time continue to express a program for APUD cell properties; (b) the establishment of such lines in some cases stringently requires, and in other cases is greatly facilitated by, conditioned medium containing as yet unknown growth factors; (c) these factors can come from either other cell cultures or nude mouse tumor stromal cells; and (d) that at least some non-small-cell lung cancers have a much less stringent growth factor requirement for establishment, have higher cloning efficiencies, and lack APUD cell properties.
TL;DR: These results demonstrate for the first time the existence of pluripotent quail neural crest cells that give rise to at least two progeny, melanocytes and neuronal cells and suggest that continuous direct interactions with noncrest cells are not required for the differentiation of these two cell types.
TL;DR: Both tumor cells and normal cells of epithelial origin are more likely to resemble their in vivo counterparts when maintained on extracellular matrix than on plastic, and when so maintained can therefore provide a better model for oncogenic studies.
TL;DR: A quantitative tissue culture assay for bovine papilloma virus (BPV) has been developed and focus formation followed single-hit kinetics, suggesting that a single particle was required for focus induction.
Journal Article•
TL;DR: The evidence in this and an accompanying paper suggests that prolactin (or related substances) has a role in the growth of some cancers of lymphoid origin in rats.
Abstract: A malignant Nb rat lymphoma which in vivo is stimulated by estrogens has been established in suspension culture. The cultured cells grew readily in Fischer's medium supplemented with fetal calf serum (10%) and 2-mercaptoethanol (10(-4) M). If horse serum was substituted for fetal calf serum, population growth ceased; i.e., cultures became "stationary." Such stationary cultures could be induced to resume active growth by the addition of a pituitary hormone, prolactin (ovine, rat); concentrations as low as 10 pg/ml had a detectable effect. In contrast, other pituitary hormones or estrogens had little or no effect. The evidence in this and an accompanying paper suggests that prolactin (or related substances) has a role in the growth of some cancers of lymphoid origin in rats.
TL;DR: A variant subline of the human acute myelogenous leukemia (AML) cell line (KG-1) has been isolated and will be useful in vitro models for investigating cellular response to CSF and for studying antigen expression in leukemic cells.
TL;DR: Conjugates containing toxin A chains coupled to monoclonal antibodies may be useful in studying functions of various cell surface components and, possibly, as tumor-specific therapeutic agents.
Abstract: We have constructed cell-specific cytotoxic agens by covalently coupling the A chain from diphtheria toxin or ricin toxin to monoclonal antibody directed against a colorectal carcinoma tumor-associated antigen. Antibody 1083-17-1A was modified by attachment of 3-(2-pyridyldithio)propionyl or cystaminyl groups and then treated with reduced A chain to give disulfide-linked conjugates that retained the original binding specificity of the antibody moiety. the conjugates showed cytotoxic activity for colorectal carcinoma cells in culture, but were not toxic in the same concentration range for a variety of cell lines that lacked the antigen. Under defined conditions virtually 100% of antigen-bearing cultured cells were killed, whereas cells that lacked the antigen were not affected. Conjugates containing toxin A chains coupled to monoclonal antibodies may be useful in studying functions of various cell surface components and, possibly, as tumor-specific therapeutic agents.
TL;DR: The morphologic and histochemical properties of the cell lines, the abnormal karyotype of C TCL-3, and the independent growth of CTCL-2 support the conclusion that most of these cell lines are of malignant origin.
Abstract: Long-term growth of lymphoblastoid T cells from tissue samples from six of six patients with cutaneous T-cell lymphoma (CTCL) and six of six patients with acute T-lymphoblastic leukemia (ALL) has been achieved by using partially purified mitogen-free human T-cell growth factor (pp-TCGF). One cell line, CTCL-2, is now independent of added growth factor; the others continue to show absolute dependency on its presence. All lines have been in continuous culture for at least 4 months and some for > 1 year. They are erythrocyte-rosette positive and are negative for Epstein-Barr virus nuclear antigen. Most of the lines are negative for Fc and complement receptors and for surface immunoglobulin except that CTCL-1 and CTCL-2 have some cells positive for these cell surface markers. Results of histochemical studies on these cell lines are similar to the known patterns for fresh cells from their disease of origin. Cell line CTCL-3 has an abnormal karyotype, but no detectable chromosomal abnormalities were found in the other lines, consistent with the karyologic features of their clinical sources. Because T cells from normal donors do not respond to pp-TCGF unless the cells are first "activated" by a lectin mitogen such as phytohemagglutinin or an antigen, the direct response to pp-TCGF of T cells from patients with T-cell neoplasias suggests that the cell lines represent a transformed neoplastic cell population. Although some of the cell lines may be normal T cells activated by the malignant cells, the morphologic and histochemical properties of the cell lines, the abnormal karyotype of CTCL-3, and the independent growth of CTCL-2 support the conclusion that most of these cell lines are of malignant origin.