Biomedical subjects
Publications and source records attributed to L B Epstein.
The chromosomal location of mouse leukocyte-interferon (IFN-alpha) genes was determined by Southern blot analysis of DNA from a panel of Chinese hamster x mouse somatic cell hybrids using a mouse IFN-alpha cDNA as a hybridization probe. All resolvable mouse genes are located on mouse chromosome 4. In addition, two common restriction site polymorphisms within these genes were identified in several mouse strains.
We have previously proposed that mice trisomic for chromosome 16 will provide an animal model of human trisomy 21 (Down syndrome). However, the value of this model is limited to some extent because trisomy 16 mouse fetuses do not survive as live-born animals. Therefore, in an effort to produce viable mice with cells trisomic for chromosome 16, we have used an aggregation technique to generate trisomy 16 diploid (Ts 16 2n) chimeras. A total of 79 chimeric mice were produced, 11 of which were Ts 16 2n chimeras. Seven of these Ts 16 2n mice were analyzed as fetuses, just prior to birth, and 4 were analyzed as live-born animals. Unlike nonchimeric Ts 16 mouse fetuses which die shortly before birth with edema, congenital heart disease, and thymic and splenic hypoplasia, all but 1 of the Ts 16 2n animals were viable and phenotypically normal. The oldest of the live-born Ts 16 2n chimeras was 12 months old at the time of necropsy. Ts 16 cells, identified by coat color, enzyme marker, and/or karyotype analyses, comprised 50-60% of the brain, heart, lung, liver, and kidney in the 7 Ts 16 2n chimeric fetuses and 30-40% of these organs in the 4 live-born Ts 16 2n animals. Ts 16 cells comprised an average of 40% of the thymus and 80% of the spleen in the Ts 16 2n chimeras analyzed as fetuses, with no evidence of thymic or splenic hypoplasia. However, we observed a marked deficiency to Ts 16 cells in the blood, spleen, thymus, and bone marrow of live-born Ts 16 2n chimeras as compared to 2n 2n controls. These results demonstrate that although the Ts 16 2n chimeras were, with one exception, viable and phenotypically normal, each animal contained a significant proportion of trisomic cells in a variety of tissues, including the brain. Furthermore, our results suggest that although the abnormal development of Ts 16 thymus and spleen cells observed in Ts 16 fetuses is largely corrected in Ts 16 2n fetuses, Ts 16 erythroid and lymphoid cells have a severe proliferative disadvantage as compared to diploid cells in older live-born Ts 16 2n chimeras. Ts 16 2n chimeric mice will provide a valuable tool for studying the functional consequences of aneuploidy and may provide insight into the mechanisms by which trisomy 21 leads to developmental abnormalities in man.
Human immune interferon (IFN-gamma) differs from leukocyte interferon (IFN-alpha) and fibroblast interferon (IFN-beta) in cell origin, inducing agents, physical and biological properties and amino acid sequence. These differences have led to interest in possible differences in the biological properties of IFN-gamma compared with IFN-alpha and IFN-beta. IFN-gamma has the same broad range of biochemical and biological actions as do IFN-alpha and IFN-beta, although relative potencies vary depending on the cell type and function investigated. There has so far been no direct evidence that IFN-gamma alters normal cell functions differently from other interferons. We report here striking qualitative and quantitative differences in the intracellular response of human fibroblasts to IFN-gamma compared with IFN-alpha and IFN-beta. Two-dimensional gel electrophoresis demonstrates, in addition to the induction of a common group of polypeptides, the existence of a set of polypeptides whose synthesis is uniquely induced by IFN-gamma.
T cells of patients with rheumatoid arthritis (RA) do not control the rate of B lymphoblast transformation induced by Epstein-Barr virus (EBV) as efficiently as T cells from healthy individuals; thus, lymphoblast cell lines are established more readily in RA lymphocytes in vitro after EBV infection. In the present experiments, we have asked whether this T cell regulation can be reproduced by lymphocytes. We found that normal T cells, activated in allogeneic or autologous mixed leukocyte reactions (MLR), produce lymphokines that inhibit in vitro EBV-induced B cell proliferation. Allogeneic MLR supernatants inhibited EBV-induced DNA synthesis 62 +/- 4% (mean +/- SE) at 10 d post-infection, whereas autologous MLR supernatants suppressed it 50 +/- 3%. RA T cell supernatants produced in an allogeneic MLR suppressed as well as normal T cell supernatants (64 +/- 5% inhibition). In contrast, supernatants from RA autologous MLR had little inhibitory activity. EBV-induced DNA synthesis at 10 d was reduced only 8 +/- 3%, compared with the 50 +/- 3% suppressive activity of normal autologous MLR supernatants. The magnitude of the proliferative responses in the autologous MLR regenerating the lymphokines was similar in the normal and RA populations. After depletion of adherent cells from the RA auto-MLR stimulators, supernatant inhibitory activities increased to normal levels (from 11 +/- 6 [SE] to 52 +/- 6% [SE]). The inhibitory factor involved in the regulation of in vitro EBV infection is a protein with a molecular weight of approximately 50,000. Its activity is eliminated by hearing at 56 degrees C and by exposure to acid at pH 2. The inhibitory activity is blocked by mixing the MLR supernatants with a polyvalent antisera or monoclonal antibodies specific for human gamma interferon. Gamma interferon produced by activating T cells in allo- or auto-MLR can reproduce T cell-mediated regulation of EBV-induced B cell proliferation, and the failure of RA auto-MLR to generate that lymphokine parallels the defective T cell regulation of EBV-induced B cell proliferation characteristic of RA lymphoid cells.
Trisomy 21 human fibroblasts are more sensitive to human interferon-alpha (IFN-alpha) than are diploid controls, consistent with the location of the gene (IFRC) which codes for the IFN-alpha receptor on chromosome 21. When compared in the antiviral assay, the difference in sensitivity is five- to tenfold, much greater than the 50% difference in IFRC gene dosage. An understanding of the mechanism by which this amplification of gene dosage occurs is relevant to the specific pathology of Down's syndrome and as a model system for studying the pathogenic effects of chromosomal aneuploidy. The enzyme (2'-5') oligoisoadenylate synthetase (2-5A synthetase), which is believed to be central to the interferon-induced antiviral response, is induced 50% more in trisomy 21 fibroblasts than in diploid controls. Thus the amplification in response occurs subsequent to the binding of IFN-alpha to its receptor and the triggering of the first set of intracellular events, the latter exemplified by the induction of 2-5A synthetase. Similar results were obtained with IFN-gamma, consistent with other evidence which indicates that a gene coding for a separate IFN-gamma receptor is also located on chromosome 21.
The biological effects on diploid and trisomy 21 human fibroblasts of pure human interferon IFLrA, a single IFN-alpha species produced from cloned DNA, were compared with those of partially purified natural IFN-alpha. Twelve interferon-induced polypeptides were visualized by two-dimensional gel electrophoresis and autoradiography. Seven of these were shown to have related primary structures and are therefore products of related genes or are related through post-translational modification. Qualitative visual comparisons and computer-aided quantitation of autoradiograms revealed no differences in the patterns of polypeptide induction following treatment with the two types of IFN-alpha, and the two interferons also induced (2'-5') oligoisoadenylate synthetase equally. By these criteria, the activities of the two interferons are qualitatively and quantitatively indistinguishable. In addition, the effects of trisomy 21 on IFLrA-induced polypeptide synthesis and on antiviral response were similar to those previously demonstrated with natural IFN-alpha.
Diminished regulation of EBV-induced B cell proliferation by T cells from patients with rheumatoid arthritis (RA) is paralleled by diminished production of gamma-interferon in response to autologous but not allogeneic stimulation. We have shown that the adherent cell subpopulation within the autologous RA stimulators plays a major role in the RA defect. In analyzing the mechanisms responsible for the adherent cell effect in RA, we examined the contribution of prostaglandin production. Indomethacin treatment (1 microgram/ml) of the RA auto-MLR led to increased production of supernatant inhibitory activity (8% +/- 4 without, 57% +/- 4 with indomethacin), but had no significant effect on the inhibition of EBV-induced B cell proliferation by normal auto-MLR supernatants. Adding excess autologous adherent cells to the normal auto-MLR, however, led to an indomethacin-reversible decline in the production of the inhibitory factor without suppressing the auto-MLR proliferative response. The adherent cell effect could be reproduced by adding PGE1 or PGE2 (10(-8) to 10(-6) M) to the normal auto-MLR. PGE2 levels in 72-hr auto-MLR supernatants were similar in RA (4.2 +/- 1 ng) and normal control (3.6 +/- 0.5 ng/ml) supernatants. Because we could not detect differences in PGE production, we assessed the sensitivity of adherent cell-depleted normal and RA auto-MLR to exogenous PGE. Concentrations of 10(-7) to 10(-6) M PGE were needed to block production of the inhibitory factor by to normal cells, whereas only 10(-13) to 10(-12) M PGE1 completely blocked it in RA cell cultures. Thus, the defective production of gamma-interferon in the RA auto-MLR is, at least in part, due to enhanced sensitivity of the RA lymphocytes to adherent cell-produced prostaglandins.
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Studies were performed with a semisolid agar culture system to determine the in vitro sensitivity of human ovarian carcinoma to human leukocyte interferon (IFN-alpha) and standard chemotherapeutic agents (adriamycin, cis-platinum, hexamethylmelamine, melphalan, and velban). Growth in culture occurred in 67% of samples derived from ascitic fluid and 71% of these exhibited reduction in tumor colony number by greater than or equal to 25% in response to 300 units interferon/ml. The responsiveness of the ascitic fluid samples to interferon ran parallel to the overall responsiveness to the other agents tested. Sensitivity to interferon was not related to the histology or grade of the tumor or to the stage of the disease. As compared with cell suspensions prepared from ascitic fluid samples, solid tumor samples had markedly lower viability, 39% vs 89%, and had more tumor cells, 81% vs 28%. Also, colonies derived from solid tumor samples were less sensitive to interferon and more sensitive to cis-platinum and adriamycin than were ascitic fluid-derived colonies. Three of four ascitic fluid samples showed a reduction in tumor colony number of greater than or equal to 25%, whereas none of the solid tumor samples obtained from the same donors were affected by interferon to that degree. Retrospective analysis of drug testing (exclusive of interferon) for in vitro: in vivo correlations revealed that in 58% of 12 evaluable situations, when a single drug (or at least one of a group of drugs) gave a positive response in vitro, stabilization or regression of the tumor occurred in vivo after treatment with the drug. These studies prove the utility of the semisolid agar culture system for assessing the antiproliferative effects of interferon against ovarian carcinoma, and will be of utility in the future for assessing whether various types of interferon have the same degree, range, and mechanism of action of antitumor effect.
Human T micron, T gamma, and T PHI lymphocyte subpopulations have the capacity to respond to phytohemagglutinin (PHA) in vitro with proliferation and the production of a pH 2 and heat-labile gamma interferon. This occurs both when the subsets are isolated by direct rosetting techniques or by negative selection. Macrophages enhance the production of the gamma interferon by each lymphocyte subset and do not themselves produce gamma interferon in response to products of PHA-activated lymphocyte subsets. Thus our studies indicate that subpopulations of T lymphocytes known to differ with regard to morphology, surface receptors, RNA content, response to corticosteroids and X-irradiation, and other functional capabilities do not differ with regard to their capacity to produce gamma interferon.
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Examples of our work concerning the production, action, and genetic control of response to interferon are reviewed. We have shown that human immune interferon is a product of mitogen stimulated T lymphocyte subsets T mu, T gamma, and T phi, and have investigated some of interferon's antiviral, antiproliferative, and antidifferentiational (or antimaturational) effects. We also have refined the genetic locus that controls response to interferon to the distal segment of the long arm of chromosome 21 in the human, and have mapped it for the first time to chromosome 16 in the mouse. We have demonstrated that imbalance of this locus in the human, as in trisomy 21, results in enhanced sensitivity of cells to interferon which, because of its immunoregulatory effects, may be involved in the abnormalities of the immune response in such patients.