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PubMed1975

Multiple active sites on human interferons.

Human interferons stimulated in peripheral leukocytes and foreskin fibroblasts are active in cultures of human and rabbit cells. The dominant factors in leukocyte and fibroblast interferons responsible for antiviral activity in rabbit cells were shown to be antigenically distinct from each other as well as from rabbit interferon. In addition, leukocyte interferon contained also a minor component with antigenic determinants characteristic of fibroblast specificity, which could be isolated by affinity chromatography on Sepharose-bound antibodies directed against firboblast interferon. Neutralization tests with selected anti-interferon sera suggested that the antiviral activities of leukocyte and fibroblast interferons in human and rabbit cells were associated with single molecules. A model is proposed where molecules of human interferon contain multiple reactive sites each of which is capable of interaction with cells of a different species. The number and distribution of these determinant sites may vary with the source of the human interferon and account for the differential in antiviral protection expressed in homologous and phylogenetically unrelated host cells.

Animals↗
PubMed1977

Human leukocytic pyrogen: purification and development of a radioimmunoassay.

Leukocytic pyrogen is a small endogenous protein that mediates fever. Because of the limitations of bioassays, circulating leukocytic pyrogen has not been demonstrated during fever in humans. The pyrogen was produced in vitro after phagocytosis of staphylococci by blood monocytes. Antibody against the pyrogen was obtained from rabbits immunized with leukocytic pyrogen and the antiserum was purified by solid-phase immunoadsorbants. Purified antibody to the pyrogen was attached to activated Sepharose 4B and used in conjunction with gel filtration to purify the pyrogen. The pyrogen was labeled with 125I and further purified by gel filtration and ion-exchange chromatography. The final preparation of 125I-labeled pyrogen demonstrated a homogeneous band during isoelectric focusing and other separation procedures. With antibody to pyrogen attached to Sepharose, less than 0.1 of a rabbit pyrogenic dose of human leukocytic pyrogen inhibited the binding of 125I-labeled pyrogen to this immunoadsorbant, and this inhibition was not affected by the presence of human serum. Thus, a radioimmunoassay for human leukocytic pyrogen has been developed that may be used to detect circulating pyrogen during fever in humans.

Antibodies↗
PubMed1977

Suppression of production of mouse 28S ribosomal RNA in mouse-human hybrids segregating mouse chromosomes.

Mouse-human somatic cell hybrids that lose (segregate) human chromosomes produce only mouse 28S ribosomal RNA even when they retain copies of the human chromosomes that contain the genes for 28S ribosomal RNA. In contrast, mouse-human hybrid cells that segregate mouse chromosomes produce only human 28S ribosomal RNA even when they have retained copies of mouse chromosomes that contain the 28S ribosomal RNA genes.

Animals↗
PubMed1977

Heteroploid conversion of human skin cells by methylcholanthrene.

Cultured epithelial cells from human skin generally had 3- to 30-fold more hydrocarbon-metabolizing activity than fibroblasts from skin of the same donor. This activity was constant for up to 55 days in primary culture but was lost rapidly upon physical subdivision of the cultures. Treatment of primary mixed fibroblasts and epithelial cell cultures with methylcholanthrene, but not phenanthrene, led to development of actively growing fibroblastic cultures with many heteroploid cells. Unique marker chromosomes, stable over a number of cell population doublings, were identified in several of the heteroploid cell strains. Pure cultures of fibroblasts from the same donors did not undergo heteroploid conversion in response to methylcholanthrene. Spontaneously occurring heteroploidy in logarithmic phase human fibroblasts is a rare event; thus, heteroploid conversion may be a useful marker for chemical transformation of human cells. Because methylcholanthrene seems to have little transforming effect on human skin fibroblasts, human skin epithelial cells, because of their hydrocarbon-metabolizing activity, may serve to convert methylcholanthrene from a distal to an ultimate carcinogenic form.

Adolescent↗
PubMed1977

Serial transfer of a human gene to rodent cells by sequential chromosome-mediated gene transfer.

The human hypoxanthine phosphoribosyl-transferase (IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) gene (hprt) has been serially transferred to mouse cells and then to Chinese hamster fibroblasts by two cycles of metaphase chromosome isolation and incubation with recipient cells. Human metaphase chromosomes were incubated with mouse A9 cells deficient in hypoxanthine phosphoribosyltransferase, and independent colonies expressing the human species form of this gene were isolated in a selective medium. Metaphase chromosomes isolated from two of these clonal lines were incubated with Chinese hamster fibroblasts deficient in hypoxanthine phosphoribosyltransferase; five resulting independent colonies again expressed the human species of this gene. The transfer frequencies in the two cycles of chromosome-mediated gene transfer were similar (about 10(-7)). These results indicate that the transferred human chromosome fragment is closely associated with the chromosomes of the mouse A9 cells and it is probably integrated into the chromosomal DNA of the recipient cell.

Animals↗
PubMed1978

Human milk stimulates DNA synthesis and cellular proliferation in cultured fibroblasts.

Human milk contains a mitogenic factor that stimulates DNA synthesis and cell division in mouse and human fibroblasts in vitro. Milk at a concentration of 1% (vol/vol) is as active in stimulating DNA synthesis as is 5% (vol/vol) human serum and 10% (vol/vol) calf serum. The mitogenic activity of human milk is destroyed by incubation with trypsin and chymotrypsin. However, neither urea, guanidine hydrochloride-dithiothreitol, nor exposure to pH 1 will inactivate the milk-derived growth factor. Gel filtration and isoelectric focusing indicate that the mitogenic activity of human milk has a molecular weight between 14,000 and 18,000 and an isoelectric point between 4.4 and 4.7.

Cell Division↗
PubMed1978

Molecular analysis of cloned human 18S ribosomal DNA segments.

A fraction of DNA from the human fetal lung fibroblast line IMR-90, 30-fold enriched for ribosomal DNA, was cloned in the lambda phage vector Charon 16A. Of 978 clones assayed by hybridization to a mixture of 125I-labeled 18S and 28S ribosomal RNA, 11 recombinants containing a 3.8-megadalton segment of human 18S ribosomal DNA were identified. Restriction endonuclease analysis of these clones demonstrated variation only in orientation of the human gene segment within the phage vector. Restriction sites that we had previously detected from analysis of restriction products of unfractionated human DNA by using the Southern transfer method were also present in the cloned DNA segment. Recombinant DNA technology thus provides a valid and efficient means to define structural conservation or variation within families of human genes.

Cell Line↗
PubMed1978

Human antibodies reactive with purified envelope antigens of primate type C tumor viruses.

Human sera from healthy individuals have been shown to react with viral antigens in preparations of detergent-disrupted C type viruses from monkeys. In this report, it is demonstrated that (populations of) these human antibodies react with highly purified envelope glycoproteins of the simian sarcoma virus-simian sarcoma-associated virus complex and the Friend leukemia virus complex. Several immunological parameters influencing human antibody binding to C type tumor virus antigens have been characterized. These parameters indicate that human antibodies tend to bind to what is probably a subset of the antigenic determinants on the virus envelope antigens and that different human sera recognize the same antigenic determinants on the virus envelope antigens tested. The possible origin of these antibodies is discussed.

Antibodies↗
PubMed1978

Rescue of immunoglobulin secretion from human neoplastic lymphoid cells by somatic cell hybridization.

B leukemia cells from four different patients were hybridized with a mouse myeloma cell line with polyethylene glycol as a fusing agent. The original leukemia cells all expressed immunoglobulin on their surface, but failed to secrete it. Over 200 different human-mouse somatic cell hybrids were obtained; 57% of them secreted human immunoglobulin in large amounts. Human immunoglobulin secretion can be a stable property of these hybrid cells over months of continuous culture. In each case the human immunoglobulin secreted was restricted to the light chain type expressed by the parental B leukemia cell. In addition, these hybrid cells secreted the original mouse myeloma protein and a variety of mixed human-mouse immunoglobulin molecules.

Animals↗
PubMed1978

Type C RNA virus-specific antibody in human systemic lupus erythematosus demonstrated by enzymoimmunoassay.

Postmortem study of proliferative glomerulonephritis associated with human systemic lumpus has previously shown that an antigen related to mammalian type C RNA viral core (p30) proteins is deposited in the renal glomerular lesions with human immunoglobulins in an immune-complex pattern. In the present work, human immunoglobulins were sequentially eluted from the lupus glomerular immune deposits and were assayed by a sensitive enzymoimmunoassay developed for the measurement of anti-p30 antibody activity against purified viral p30 proteins of mammalian type C viruses. Human immunoglobulins showing specific anti-p30 antibody activity, particularly against p30 antigen of feline endogenous virus RD-114 and to a smaller extent against p30 antigen of murine type C virus, were eluted by acid buffer from the glomerular immune deposits in two patients with lupus proliferative glomerulonephritis who have deposits of viral p30-related antigen in the same tissue lesions. This study adds support for the hypothesis that expression of type C viral antigen may be involved in the multifactorial pathogenesis of proliferative glomerulonephritis associated with human systemic lupus.

Antibodies, Viral↗
PubMed1978

Study of antibodies against human melanoma produced by somatic cell hybrids.

We fused spleen lymphocytes obtained from mice immunized against a human melanoma cell line and melanoma-mouse hybrid cells with the P3 X 63 Ag8 mouse myeloma in order to produce hybrids secreting antibodies against a human melanoma. Antibodies secreted by individual hybrids were tested for their reaction with a panel of human melanoma, colorectal carcinoma, and normal cells in an indirect radioimmunoassay, and they displayed different specificities and crossreactivities. Some reacted only with melanomas, whereas others crossreacted with normal human or human colorectal carcinoma cells. By analysis of competitive binding of mixtures of monoclonal antibodies, it was possible to delineate different epitopes on melanomas. Hybrids growing in nude mice and producing antimelanoma antibody suppressed growth of melanoma tumors.

Animals↗
PubMed1979

Molecular cloning of human epsilon-globin gene.

Human beta-like globin genes were investigated by use of rabbit beta-globin cDNA plasmid as a cross-species hybridization probe. Normal and beta 0/delta beta 0 thalassemic DNA were compared by filter hybridization procedures. It proved possible to demonstrate that the rabbit probe detected G gamma, A gamma, delta, beta, beta 0, and delta beta 0 human globin genes as well as an additional unidentified beta-like globin gene. By use of an agarose gel elution procedure, fractions of HindIII-digested DNA enriched for beta-like globin genes were purified. One of these fractions, 8.0 kilobases in size, was clonedinto lambda 788, and EK2 lambda HindIII vector. A positive clone was obtained and characterized by restriction mapping and sequence analysis. The sequence data obtained predicted an amino acid sequence that exactly matches a part of human epsilon-globin. The human non-alpha-globin locus is now nearly complete. delta, beta, and gamma human globin genes have already been cloned and analyzed. We describe here the cloning of the remaining non-alpha-globin gene, epsilon.

Amino Acid Sequence↗
PubMed1979

Semisynthesis of human somatotropin analogs.

Complementation of the natural NH2-terminal 134-amino acid fragment of the reduced, carbamoylmethylated human somatotropin with synthetic analogs of COOH-terminal fragments of 57, 42, or 38 amino acids of reduced, carbamoyl-methylated human somatotropin has been investigated. It was found that synthetic fragments of 57 and 42 amino acids gave recombinants with full growth-promoting activity, whereas attempts to obtain a recombinant with the synthetic 38-amino acid fragment were unsuccessful. The synthesis of two analogs of the COOH-terminal fragment of human somatotropin, human [N]e170, Ala165,182,189] somatotropin-(150-191) and human [Nle170, Ala165,182,189] somatotropin-(154-191), is herein described.

Amino Acid Sequence↗
PubMed1979

Identification of transferrin receptors on the surface of human cultured cells.

We have examined the binding of human transferrin to cultured human choriocarcinoma cell lines and to detergent extracts of such cells. The results indicate the presence of a high-affinity saturable binding site (Ka = 4.25 x 10(8) M-1) that is specific for transferrin. This receptor has also been detected on three other human cell lines of different phenotypic origin, including Wil-2 (splenic lymphocytes of B-cell origin), RPMI-2650 (a quasi-diploid nasopharyngeal carcinoma), and WI-38 (embryonic lung fibroblasts). By using anti-human transferrin antiserum to immunoprecipitate the receptor-transferrin complex from detergent extracts of cells containing saturating levels of transferrin followed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, a single polypeptide of 90,000 daltons has been identified as a subunit of the putative transferrin receptor. The protein shows immunochemical identity and coelectrophoreses in sodium dodecyl sulfate gels with a cell surface glycoprotein subunit, previously identified in placental brush border membrane preparations, on all human cultured cell lines examined. These results suggest that the recent demonstration of transferrin dependence of maximal cell growth in culture [e.g., Hutchings, S.E. & Sato, G.H. (1978) Proc. Natl. Acad. Sci. USA 75, 901-904] is mediated through expression of this glycoprotein receptor.

Cell Line↗
PubMed1979

Human melanoma cells have both nerve growth factor and nerve growth factor-specific receptors on their cell surfaces.

Human melanoma cells were examined in an indirect membrane immunofluorescence assay for surface nerve growth factor (NGF) and NGF receptors. This assay revealed that human melanoma cells have various levels of NGF and NGF receptors on the plasma membrane, whereas a variety of human sarcoma and carcinoma tumor cells and normal human fibroblasts are negative. Surface NGF could be detected on melanoma cells with a rabbit antiserum directed to NGF at titers as high as 1:64; prior adsorption of this antibody with mouse 2.5S NGF resulted in a loss of fluorescence. The melanoma cells were positive whether or not they were grown in the presence of fetal calf serum. NGF production by human melanomas is a previously unrecognized property of this differentiated cell type. Although other cells in culture have been shown to produce NGF, the association of NGF production with the presence of NGF receptors on the cell surface is rare among tumor cells, and may represent an opportunity for "autostimulation" of melanoma cells by this growth factor.

Cell Line↗
PubMed1979

Induction of rat sarcomas in rats treated with antithymocyte sera after transplantation of human cancer cells.

Human cancer cells that had had high (greater than 160) tissue culture passages, when transplanted into antithymocyte-treated F344 newborn rats, caused induction of rat sarcomas in the rats within 2 or 3 subcultures, whereas human cancer cells with low (5-33) passages in vitro did not cause overt induction of rat sarcomas until after 5-10 subtransplantations. Because oncornavirus activity was not detected in either rat or human tumors, it is suggested that transforming sequences located on the human tumor cells may have been transferred to supporting rat reticulum cells in close contact with the human cancer cells.

Animals↗
PubMed1976

Lysis of RNA tumor viruses by human serum: direct antibody-independent triggering of the classical complement pathway.

In earlier studies we found that human serum, but not serum from multiple other species, inactivated and lysed oncornaviruses from a number of diverse sources in the apparent absence of antibody. A detailed analysis of the role of the human complement (C) system in mediating this lytic process indicates that human C1q interacts directly, in the absence of immunoglobulin, with oncornaviruses. Binding of C1 via C1q in this manner leads to activation of C1r, C1s, and thus of the classical C pathway. Integrity of the classical pathway is an absolute requirement for lysis although activation of the alternative pathway considerably amplifies the amount of lysis obtained, possibly through involvement of the C3b-dependent feedback mechanism. Activation of C is accompanied by deposition of C components on the viral surface and lysis on completion of the C reaction sequence. Thus in this system, the C1q subunit of C1 subserves a specific recognition function normally associated with antibody. This ability of human serum to inactivate oncornaviruses may represent a natural defense mechanism operative in vivo which deters expression of intact oncornaviruses in human malignancies.

Cell Survival↗
PubMed1978

Synthesis of fibronectin by cultured human endothelial cells.

Plasma fibronectin is probably the major nonimmune particulate opsonin in blood and is cross-linked to fibrin during the final stage of blood coagulation. Fibronectin also occurs in an insoluble form in basement membranes especially those underlying endothelial cells and in loose connective tissue. Fibronectin was demonstrated in cultured human endothelial cells and in the surrounding extracellular matrix by immunofluorescence microscopy by using antibody to human plasma fibronectin. Cultured human endothelial cells released fibronectin into the culture medium which was immunologically identical to the fibronectin in human plasma. Cultured human endothelial cells were labeled with [3H] leucine. The radioactive fibronectin present in the endothelial postculture medium and in urea extracts of cellular monolayers was isolated with either anti-fibronectin coupled to Protein A-Sepharose or double antibody immunoprecipitation and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When reduced, the [3H] fibronectin synthesized by cultured endothelial cells had the same mol wt (approximately 200,000) as plasma fibronectin. Unreduced, the [3H] fibronectin synthesized by endothelial cells migrated as a dimer, as did plasma fibronectin. Fibronectin accounted for approximately 15% of the protein synthesized and released by endothelial cells into the culture medium. Thus, cultured endothelial cells synthesize fibronectin, secrete it into the culture medium, and incorporate it into extracellular matrix. The results suggest that the endothelial cell is potentially a major site of synthesis of circulating plasma fibronectin. In addition, fibronectin derived from endothelial cells may be an important structural component of the subendothelium.

Cells, Cultured↗