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Biomedical subjects

L B Epstein

Publications and source records attributed to L B Epstein.

At least 37 records · Page 2Linked to original sources
PubMed1990

Coordinated induction of autocrine tumor necrosis factor and interleukin 1 in normal human monocytes and the implications for monocyte-mediated cytotoxicity.

Cytokine production and cytotoxicity for tumor cells are two important aspects of monocyte function and the inflammatory response against tumors and infectious agents. In the present studies we provide direct evidence at the mRNA and protein levels for the existence of autocrine tumor necrosis factor (TNF) and its importance as a mediator of human monocyte cytotoxicity for WEHI-164 tumor cells. The induction of TNF and interleukin 1 beta (IL-1 beta) mRNA by exogenous TNF or IL-1 beta, as determined by Northern blot analysis, is time dependent in normal human monocytes isolated by countercurrent elutriation. With either TNF or IL-1 beta as the stimulus, TNF mRNA is induced first, peaks within 1-3 h, and declines to nearly undetectable levels by 9 h. TNF mRNA accumulation is enhanced in the presence of cycloheximide indicating that de novo protein synthesis is not required for maximal TNF mRNA induction. In contrast, IL-1 beta mRNA is induced later, peaks at 3-9 h, and remains considerably elevated at 18 h. IL-1 beta mRNA accumulation is partially suppressed in the presence of cycloheximide. TNF and IL-1 beta protein production as assayed by specific enzyme-linked immunosorbent assays correlates well with respective mRNA induction. Both TNF and IL-1 beta enhance monocyte cytotoxicity as single agents; however, their combined effect is less than additive. When both agents are combined, TNF mRNA levels, as assessed by densitometric analysis of slot blots, are approximately equal to those induced by TNF alone. In contrast, IL-1 beta mRNA levels are additive. Our studies provide evidence for highly coordinated and interrelated pathways of autocrine TNF and IL-1 induction in human monocytes and demonstrate the role of TNF and IL-1 in regulating monocyte-mediated cytotoxicity for tumor cells.

Autoradiography↗
PubMed1990

Decreased level of T cell receptor expression by Down syndrome (trisomy 21) thymocytes.

Individuals with Down syndrome (DS) have an enhanced susceptibility to viral and bacterial infections. Previous studies by our laboratory demonstrated alterations in the proportions of peripheral T cell subpopulations and decreased proliferative, interleukin-2, and antibody responses to viral and bacterial antigens in DS. These data suggested that DS lymphocytes have a diminished ability to recognize and respond to specific antigen. It has been proposed that the abnormalities in T cell function in DS may be a result of aberrant T cell maturation within the DS thymus. Therefore, we examined by immunofluorescence and flow cytometry the cell surface expression of the alpha,beta chains of the T cell receptor (TCR alpha,beta) and the associated CD3 molecule on thymocytes from 10 DS and 27 control children. A significantly smaller proportion of cells expressing high levels of TCR alpha,beta was observed in DS thymuses compared to controls (17.0% vs. 34.3%, respectively; P less than 0.01). A similar observation was made for CD3, a molecule responsible for signal transduction through the TCR, where a lower proportion of cells expressing high levels of CD3 was found in DS compared to controls (18.4% vs. 43.3%, respectively; P less than 0.001). These data are evidence for aberrant T cell maturation in DS. In addition, our findings of decreased acquisition of high levels of the molecules which are critical for antigen-specific recognition by T cells suggest a possible mechanism for the decreased T cell function found in individuals with DS.

Antigens, CD↗
PubMed1990

Synergistic induction of polypeptides by tumor necrosis factor and interferon-gamma in cells sensitive or resistant to tumor necrosis factor: assessment by computer based analysis of two-dimensional gels using the PDQUEST system.

Tumor necrosis factor (TNF) synergistically enhanced the antiproliferative activity of interferon-gamma (IFN-gamma) in both TNF-sensitive and TNF-resistant variants of the cervical carcinoma line, ME-180. TNF alone had no apparent effect on the levels of synthesis of individual proteins in either of these variant cell lines as assessed by computerized two-dimensional gel analysis of cell lysates using the PDQUEST system. However, IFN-gamma enhanced the levels of 18 polypeptides and suppressed the levels of 10 polypeptides in both cell lines. When used in combination in both cell lines, TNF and IFN-gamma induced the synthesis of 10 polypeptides that were not induced by either agent alone. These synergistically induced polypeptides may be crucial to the mechanism of the synergistic antiproliferative action of TNF and IFN-gamma in ME-180 cells.

Cell Division↗
PubMed1990

Down syndrome (trisomy 21) thymuses have a decreased proportion of cells expressing high levels of TCR alpha, beta and CD3. A possible mechanism for diminished T cell function in Down syndrome.

T cell differentiation antigen expression by thymocytes from nine individuals with Down syndrome (DS) and 27 controls was examined using immunofluorescence and flow cytometry. We found no significant differences between DS and controls in the proportion of CD1+ or CD2+ cells or in the percentages of CD4-8-, CD4+8+, CD4-8+, or CD4+8- cells. However, a significantly smaller proportion of cells expressing high levels of T cell receptor alpha, beta (TCR alpha, beta) was observed in DS thymuses compared to controls (28.0% vs 47.5%, respectively; P less than or equal to 0.01). A similar observation was made for CD3, a signal-transducing complex for the TCR, where the proportion of cells expressing high levels of CD3 in DS was 24.3% compared to 53.3% for controls (P less than or equal to 0.001). These data demonstrate aberrant T cell maturation in DS. Furthermore, our observation of diminished expression of critical molecules for antigen-specific recognition by T cells suggests a possible mechanism for decreased T cell function in DS.

Antigens, CD↗
PubMed1989

In vitro evaluation of 6-thioguanine and alpha-interferon as a therapeutic combination in HL-60 and natural killer cells.

The effect of 6-thioguanine (6-TG) and alpha-interferon (IFN-alpha) was evaluated in vitro to determine their effectiveness in combination on the therapeutically relevant events of: HL-60 cell cytotoxicity, HL-60 cell differentiation, and natural killer (NK)-cell mediated cytotoxicity. 6-TG was toxic to HL-60 cells (ID50 = 0.6 microM; 24-h exposure) while IFN-alpha (up to 1000 IU/ml) had minimal cytotoxic activity. Sequence-dependent activity was observed, inasmuch as the IFN-alpha pretreatment sequence was antagonistic, while the other schedules were additive or, possibly, synergistic. The combination of 0.5 microM 6-TG and 100 IU/ml IFN-alpha produced the same level of HL-60 cell differentiation as each agent alone, suggesting no benefit from the combination on this process. The effect of 6-TG and IFN-alpha on NK cell-mediated cytotoxicity was found to be sequence dependent. NK cell activity was markedly stimulated by IFN-alpha, whereas 6-TG alone seemed to have no direct effect. However, when the NK cells were pretreated with 100 IU/ml IFN-alpha followed by 10 microM 6-TG, the IFN-alpha-enhanced activity of NK cells was ablated. These results suggest that the immunosuppressive activity of 6-TG may be related to the acute inhibition of cytokine activation. Our results suggest that 6-TG and IFN-alpha have considerable interactions, which are sequence dependent. The optimal sequence for potential therapeutic application of these anticancer agents appears to be 6-TG pretreatment followed by IFN-alpha.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

Biphasic platelet-activating factor synthesis by human monocytes stimulated with IL-1-beta, tumor necrosis factor, or IFN-gamma.

The capacity of IL-1-beta, TNF, and IFN-gamma to stimulate platelet-activating factor (PAF) synthesis by human monocytes is examined in our report. All three cytokines induced PAF synthesis in a novel biphasic pattern with peaks of PAF synthesis 1 to 2 and 6 to 8 h after stimulation of the monocytes. In contrast, calcium ionophore A23187 elicited a single peak of early PAF synthesis. PAF in the early peak was largely retained intracellularly whereas PAF in the late peak was largely released into culture fluids. Combinations of cytokines were subadditive or antagonistic in inducing PAF synthesis. Cycloheximide inhibited the late peak of PAF synthesis indicating that protein synthesis is required for synthesis of the phospholipid PAF. Specific antibodies to TNF or IL-1-beta inhibited the late peak of PAF synthesis induced by IFN-gamma indicating that late PAF synthesis is dependent on cytokine synthesis. The quantities of PAF produced by cytokine-activated monocytes are sufficient to activate human monocytes. Thus, these studies suggest that PAF may mediate in part monocyte activation by cytokines.

Adult↗
PubMed1988

Overlapping polypeptide induction in human fibroblasts in response to treatment with interferon-alpha, interferon-gamma, interleukin 1 alpha, interleukin 1 beta, and tumor necrosis factor.

Cytokine-induced polypeptides were identified in whole cell lysates of human fibroblasts by computer-based analysis of two-dimensional gels with the use of the PDQuest System. Treatment with interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma) enhanced the synthesis of 12 and 28 polypeptides, respectively. Exposure to interleukin 1 alpha (IL-1 alpha) or interleukin 1 beta (IL-1 beta) resulted in the increased synthesis of seven identical polypeptides. Treatment with tumor necrosis factor (TNF) at 100 U/ml led to enhanced expression of seven polypeptides, whereas exposure to TNF at 1000 U/ml increased the levels of these seven plus two additional polypeptides. The antiviral and antiproliferative effects of these cytokines in strain 153 fibroblasts were also assessed. Both IFN-alpha and IFN-gamma exhibited antiviral activity, whereas both IL-1 and TNF stimulated fibroblast growth. IFN-gamma was alone in inhibiting proliferation. Thus, although these cytokines exhibit low degrees of structural homology, they share some common functions, and a number of polypeptides were induced in common by two or more of these agents. The greatest similarities in polypeptide induction occur between IFN-alpha and IFN-gamma and between the IL-1s and TNF. However, polypeptides were also induced in common by IFN-alpha and TNF, IFN-gamma and IL-1, and IFN-gamma and TNF. These similarities in polypeptide induction may reflect the overlapping functions of these cytokines and may be indicative of common biochemical pathways in their mechanisms of action.

Biological Products↗
PubMed1986

Structure-activity studies of interleukin-2.

The critical role of interleukin-2 (IL-2) in immune response heightens the need to know its structure in order to understand its activity. New computer-assisted predictive methods for the assignment of secondary structure together with a method to predict the tertiary structure of a protein from data on its primary sequence and secondary structure were applied to IL-2. This method generated four topological families of structures, of which the most plausible is a right-handed fourfold alpha-helical bundle. Members of this family were shown to be compatible with existing structural data on disulfide bridges and monoclonal antibody binding for IL-2. Experimental estimates of secondary structure from circular dichroism and site-directed mutagenesis data support the model. A region likely to be important in IL-2 binding to its receptor was identified as residues Leu36, Met38, Leu40, Phe42, Phe44, and Met46.

Amino Acid Sequence↗
PubMed1986

Abnormalities of the in vitro cellular and humoral responses to tetanus and influenza antigens with concomitant numerical alterations in lymphocyte subsets in Down syndrome (trisomy 21).

Peripheral blood leukocytes (PBL) from noninstitutionalized individuals with trisomy 21, paired with closely age-matched and/or family members as controls, were analyzed for different aspects of their cellular and humoral immune responses, and were phenotypically characterized by means of various monoclonal antibodies. Both the in vitro PBL proliferative and antibody responses to a bacterial antigen (tetanus toxoid) and to viral antigens (influenza A/Bangkok and B/Singapore) were significantly decreased in trisomy 21. In addition, bacterial and viral antigen-induced in vitro interleukin 2 (IL 2) production was markedly reduced, although mitogen (PHA)-stimulated IL 2 production was not impaired. The functional abnormalities observed in trisomy 21 PBL occur concomitantly with numerical alterations in circulating lymphocyte subsets in these same individuals. Although no difference was observed between the trisomic and control groups in the percentage of total T and B lymphocytes, a decreased level of Leu-3a + 3b-positive cells (T helper/inducer cells) and an increased level of Leu-2a-positive cells (T suppressor/cytotoxic cells) that co-expressed Leu-15 (suppressor alone) were noted.

Adolescent↗
PubMed1986

The mouse IFN-alpha (Ifa) locus: correlation of physical and linkage maps by in situ hybridization.

The physical location of the mouse IFN-alpha locus (Ifa) on chromosome 4 was defined by in situ hybridization of a cloned mouse IFN-alpha probe to metaphase spreads in which one chromosome 4 was present as part of a single metacentric chromosome, all other chromosomes being acrocentric. (This approach greatly facilitates analysis and can be used even when it is difficult to obtain good banding). Using unbanded chromosomes, the grains were localized over the chromosome 4 part of the metacentric, in a region 0.61 +/- 0.07 (SD) of the distance from the centromere to the telomere. In Giemsa-banded spreads, the majority of the grains were in the region 4C3----C6. Consideration of these results and of the known linkage maps for mouse and man indicates that the Galt - Aco-1 - Ifa syntenic group spans a distance of approximately 14 cM and suggests that the same group on human 9p will also occupy a similarly sized region, with GALT proximal and IFL distal to the centromere.

Animals↗
PubMed1985

Stem cell deficiencies and thymic abnormalities in fetal mouse trisomy 16.

Mouse fetuses with trisomy 16 have severe abnormalities of several hematopoietic stem cell and precursor populations. The thymus is extremely hypoplastic, with a greater than or equal to 80% reduction in the number of thymocytes. This cellular deficiency appears to be the result of a deficiency in the number of precursor cells in the early thymus, since the rate of proliferation of thymocytes in explanted day-14 thymuses was normal. However, the functional maturation of thymocytes was delayed in vitro in day-17 organ explants, although the maximal response to the mitogenic and interleukin 2-stimulating effects of concanavalin A are quantitatively normal. B cells and pre-B cells in the fetal liver were moderately decreased, but the ability of fetal liver cells to be transformed by Abelson murine leukemia virus was nearly totally lost. There were also significant relative and absolute decreases in the number of spleen, culture, and erythroid colony-forming units (CFU-S, CFU-C, CFU-E) and of erythroid burst-forming units (BFU-E) in the trisomic liver, and the trisomic animals were anemic with small spleens and livers. However, unlike other genetically caused anemias, there was no reduction in the number of germ cells. The hematopoietic abnormalities in the trisomy 16 mouse, involving the lymphoid, myeloid, and erythroid cell lineages, are much more generalized than the abnormalities in any of the other described genetically caused immunodeficiencies or anemias in the mouse. They are also more severe than those in human trisomy 21 (Down syndrome), for which mouse trisomy 16 is a genetic model, but there does exist an interesting parallel between the thymic abnormalities in the two species.

Animals↗
PubMed1985

Ichthyosis and neutral lipid storage disease.

Four members of a consanguineous middle eastern family had a lipid storage disease characterized by congenital ichthyosiform erythroderma, neurosensory deafness, cataracts, mild myopathy, and leukocyte vacuoles. These patients are similar to several others recently reported and represent a unique disorder of lipid metabolism. The clinical and biochemical manifestations of this lipid storage disease are reviewed. Evidence is presented that the disorder is inherited as an autosomal recessive trait, and that heterozygotes may be detected by the presence of vacuoles within circulating eosinophils.

Adolescent↗