Effect Of Suppressor Research Articles

Isochromosome 17q in Blast Crisis of Chronic Myeloid Leukemia and in Other Hematologic Malignancies Is the Result of Clustered Breakpoints in 17p11 and Is Not Associated With Coding TP53 Mutations

An isochromosome of the long arm of chromosome 17, i(17q), is the most frequent genetic abnormality observed during the disease progression of Philadelphia chromosome-positive chronic myeloid leukemia (CML), and has been described as the sole anomaly in various other hematologic malignancies. The i(17q) hence plays a presumably important pathogenetic role both in leukemia development and progression. This notwithstanding, the molecular consequences of this abnormality have not been investigated in detail. We have analyzed 21 hematologic malignancies (8 CML in blast crisis, 8 myelodysplastic syndromes [MDS], 2 acute myeloid leukemias, 2 chronic lymphocytic leukemias, and 1 acute lymphoblastic leukemia) with i(17q) by fluorescence in situ hybridization (FISH). Using a yeast artificial chromosome (YAC) contig, derived from the short arm of chromosome 17, all cases were shown to have a breakpoint in 17p. In 12 cases, the breaks occurred within the Smith-Magenis Syndrome (SMS) common deletion region in 17p11, a gene-rich region which is genetically unstable. In 10 of these 12 cases, we were able to further map the breakpoints to specific markers localized within a single YAC clone. Six other cases showed breakpoints located proximally to the SMS common deletion region, but still within 17p11, and yet another case had a breakpoint distal to this region. Furthermore, using chromosome 17 centromere-specific probes, it could be shown that the majority of the i(17q) chromosomes (11 of 15 investigated cases) were dicentric, ie, they contained two centromeres, strongly suggesting that i(17q) is formed through an intrachromosomal recombination event, and also implicating that the i(17q), in a formal sense, should be designated idic(17)(p11). Because i(17q) formation results in loss of 17p material, potentially uncovering the effect of a tumor suppressor on the remaining 17p, the occurrence of TP53 mutations was studied in 17 cases by sequencing the entire coding region. In 16 cases, no TP53 mutations were found, whereas one MDS displayed a homozygous deletion of TP53. Thus, our data suggest that there is no association between i(17q) and coding TP53 mutations, and that another tumor suppressor gene(s), located in proximity of the SMS common deletion region, or in a more distal location, is of pathogenetic importance in i(17q)-associated leukemia.

Dual effects of suppressor of cytokine signaling (SOCS-2) on growth hormone signal transduction

A family of suppressors of cytokine signaling (SOCS) has recently been identified of which two members have been shown to block growth hormone (GH) signaling. Dose-response experiments were conducted in 293 cells and SOCS-1 and SOCS-3 were shown to inhibit the transcriptional activation of a GH-responsive element and suppressed Jak2 tyrosine kinase activity. SOCS-2 had two opposite effects: at low concentrations it inhibited GH-induced STAT5-dependent gene transcription, but restoration of GH signaling was observed at higher concentrations. In cotransfection studies, SOCS-2 was able to block the inhibitory effect of SOCS-1 but not that of SOCS-3 on GH signaling. These findings suggest that a major function for SOCS-2 is to restore the sensitivity to GH by overcoming the initial inhibitory effects of other endogenous SOCS molecules.

Insertions of hybrid P elements in the yellow gene of Drosophila cause a large variety of mutant phenotypes.

A series of yellow mutations associated with a great variety of tissue-specific phenotypes were obtained from several highly unstable Drosophila melanogaster strains carrying the gypsy-induced y2 allele. These mutations are caused by insertion of additional DNA sequences of variable size 69 bp upstream of the yellow transcription start site. These sequences are flanked by identical copies of a deleted 1.2-kb P element arranged in the same or inverted orientation. The central part of the inserted element consists of genomic sequences originating from different regions of the X chromosome. The mutant phenotype caused by these chimeric elements depends on the nature of the sequences present either in the P element or in the central part of the insertion, suggesting that these sequences are able to affect expression of the yellow gene. In addition, sequences present in the central region of the insertions strongly modify the effects of the gypsy-bound suppressor of Hairy-wing [su(Hw)] and modifier of mdg4 [mod(mdg4)] proteins on yellow transcription. Analyses of these mutations give new insights into the mechanisms by which su (Hw) and mod(mdg4) affect enhancer function.

Studies on system performance and sensitivity in ion chromatography

Improvements in HPLC instrumentation, suppressor technology and ion-exchange columns have occurred over the past several years to the point where an ion chromatograph can now be configured for anion analysis using a considerable variety of hardware, suppressor and column combinations. A number of parameters, including hardware configuration, effect of temperature, column type and suppressor device, were studied with a view toward optimizing the performance of an ion chromatographic (IC) system. It was found that dual-piston, reciprocating pumps used with low-pressure pulse dampeners significantly reduced baseline noise for both suppressed and non-suppressed conductivity detector combinations, while column temperature control proved essential in order to achieve routine sub-ppb detectability in non-suppressed IC. In general, the use of suppressed IC resulted in lower detection limits than non-suppressed IC when using the same columns and hardware. Of the columns studied, the methacrylate-based HR column was found to give the best overall separation selectivity when using a carbonate-bicarbonate eluent and suppressed conductivity detection. The majority of column and suppressor combinations evaluated gave acceptable performance, although some gave less than satisfactory results. Also, some combinations resulted in lower than expected analytical results, particularly for chloride, when quantitated using single-point calibration. In addition to the use of commercially available suppressor devices, there is also a large number of high-capacity cation exchangers which can be used as suppressors and these columns, in some instances, may offer equivalent (or superior) performance compared to the commercial devices.

Suppression of the Activation of Chitinase and .BETA.-1,3-Glucanase in Pea Epicotyls by Endogenous Suppressor from Pisum sativum.

Healthy pea plants contain a factor, as called an endogenous suppressor, which suppresses the accumulation of pisatin induced by the elicitor from a pea pathogen, Mycosphaerella pinodes. The effects of the endogenous suppressor on the activation of pathogenesis-related proteins (PR-proteins) such as chitinase and β-1, 3-glucanase were examined. The fungal elicitor induced the activations of these enzymes in pea, kidney bean and soybean, however, the concomitant presence of the endogenous suppressor with the fungal elicitor resulted in suppression of activations of these enzymes in only pea but not in kidney bean or soybean. In contrast, the endogenous suppressor alone rather activated these enzymes in kidney bean and soybean to which M. pinodes is nonpathogenic. Thus, the action of endogenous suppressor on the activation of PR-proteins is species-specific as well as that on the production of phytoalexins. Together with our previous report, these findings show that the pea endogenous suppressor may have a potential to block the general resistance of its producer and that it is quite similar to the exogenous suppressor from M. pinodes with respect to the biological activities.

Dominant effects of suppressor of Hairy-wing mutations on gypsy-induced alleles of forked and cut in Drosophila melanogaster.

Mutations induced by the gypsy retrotransposon in the forked (f) and cut (ct) loci render their expression under the control of the suppressor of Hairy-wing [su(Hw)] gene. This action is usually recessive, but su(Hw) acts as a dominant on the alleles fk, ctk and ctMRpN30. Molecular analysis of the gypsy element present in fk indicates that this allele is caused by the insertion of a modified gypsy in which the region normally containing twelve copies of the octamer-like repeat that interacts with the su(Hw) product is altered. Analysis of the gypsy element responsible for the ctk and ctMRpN30 mutations also reveals a correlation between the dominant action of su(Hw) and disruption of the octamer region. We propose that these disruptions alter the affinity and interaction of su(Hw) protein with gypsy DNA, thereby sensitizing the mutant phenotype to fluctuations in su(Hw) product.

Two-tone suppression in inner hair cell responses: Correlates of rate suppression in the auditory nerve

Inner hair cell (IHC) recordings were made from second turn of the guinea pig cochlea where characteristic frequencies are approximately 4000 Hz. In order to compare IHC responses with rate suppression measured in the auditory nerve, suppressors were introduced that produced little or no response in the hair cell. The effects of a variable-frequency suppressor on a constant-frequency probe, placed near characteristic frequency, were also investigated since this paradigm is commonly used in single unit experiments. Resulting magnitude changes were measured in the fundamental component of the ac receptor potential and/or in the total de produced in the region of temporal overlap between the two stimulus inputs. This latter component is escecially important when considering how changes in IHC responses relate to decreases in discharge rate in single auditorynnerve fibers. Since the ac receptor potential is filtered by the hair cell's basolateral membrane, the dc component probably controls transmitter release at the characteristic frequency of these second-turn IHCs. Based on results from these and previous experiments, a proposal is advanced to explain the evolution of two-tone suppression in the peripheral auditory system. The paper also discusses the use of excitatory versus non-excitatory suppressors and includes a description of two-tone suppression areas at the mechanical, IHC and single unit levels. The explanation of low-side suppression areas is of special interest since hitherto they have been difficult to model (Kim, 1985).

T cell regulation of the antibody response to bacterial polysaccharide antigens: an examination of some general characteristics and their implications.

The characteristics of thymus-derived (T) lymphocytes that regulate the magnitude of the antibody response to the capsular polysaccharide antigen of type III Streptococcus pneumoniae are considered within the context of a general homeostatic model for controlling the antibody response to microbial antigens of medical importance. Some experimental approaches are described in which the activities of such regulatory T cells are modulated to provide an increase in the development of host immunity, to improve the immunogenicity of poorly immunogenic antigens, or to eliminate the inhibitory effects of suppressor T cells.

Effects of Cryptococcus neoformans-specific suppressor T cells on the amplified anticryptococcal delayed-type hypersensitivity response

Cell-mediated immunity is an important host resistance mechanism against Cryptococcus neoformans, the etiological agent of cryptococcosis. Previous studies from our laboratory have shown that the anticryptococcal cell-mediated immune response as measured by delayed-type hypersensitivity (DTH) is down-regulated by a cascade of antigen-specific T suppressor (Ts) cells. Recently, we have identified a population of CD4 T cells that up-regulate the anticryptococcal DTH response (Tamp cells). The Tamp cells are found in the spleens of donor mice at 6 days after immunization with cryptococcal antigen, and they amplify the anticryptococcal DTH response when transferred to syngeneic recipients at the time of immunization of the recipients. In this study, we determined the effects of C. neoformans-specific Ts cells on the induction of the Tamp cells in the Tamp cell-donor mice and on the induction and expression of the amplified anticryptococcal DTH response in the Tamp cell-recipient mice. When cryptococcal-specific Ts1 cells were given at the time of immunization of the Tamp cell-donor mice, induction of Tamp cells was inhibited. In contrast, when Ts1 cells were given at the time of adoptive transfer of Tamp cells, the recipients displayed amplified DTH responses, indicating that Ts1 cells do not affect the Tamp cells' function once the Tamp cells have been produced. C. neoformans-specific Ts2 cells given at the time of either immunization or footpad challenge of the Tamp cell-recipient mice did not alter, to any measurable extent, the amplified DTH response. These results indicate that in addition to amplifying the anticryptococcal DTH response, Tamp cells may protect the anticryptococcal TDH cells from suppression by C. neoformans-specific Ts cells, much like contrasuppressor cells do in other systems. However, further characterization of the Tamp cells revealed that they are not adherent to Viscia villosa lectin, indicating that the anticryptococcal Tamp cells do not have this characteristic in common with contrasuppressor cells of other antigen systems.

An assessment of the effects of swainsonine on survival of mice injected with B16-F10 melanoma cells

Systemic administration of swainsonine, an indolizidine alkaloid, inhibits the experimental metastasis of B16-F10 murine melanoma cells. This activity can be attributed primarily to swainsonine-mediated enhancement of host natural killer cell activity. As one next step towards investigating the potential therapeutic utility of this drug, its efficacy in enhancing host survival in the same B16-F10 model system has been assessed. In studies employing intravenously injected tumor cells, pretreatment of mice with swainsonine-containing drinking water provided a reproducible protective effect for the host. This prolongation of survival was substantially enhanced when swainsonine was administered in combination with either of two other immunomodulators, polyinosinic: cytidylic acid (poly-IC) or interleukin-2. In studies in which combinations of these agents were administered after intravenous injection of tumor cells, or after subcutaneous implantation, a greatly reduced effect on host survival was observed. However, when used in combination with cyclophosphamide (to block the effects of suppressor T cells), swainsonine did increase mean survival time. The implications of these results for the use of swainsonine in treatment of metastatic or localized disease, together with its potential mechanism(s) of action, are discussed.

DIFFERENTIAL REGULATION OF ACTIVATION-ASSOCIATED RECEPTOR EXPRESSION ON CD4− AND CD8-POSITIVE T LYMPHOCYTES BY ALLOSENSITIZED SUPPRESSOR T CELLS

We have demonstrated by two-color flow cytometry that allosensitized human suppressor T cells thwart progression of alloactivated T cells into the G1B stage of the cell cycle, and consequently prevent the expression of transferrin receptors on the majority of alloreactive MLR responder cells (P less than 0.005). Suppressor cells inhibit transferrin as well as interleukin-2 receptor expression on both CD4- and CD8-positive responder cells. The addition of 20 U/ml of recombinant interleukin-2 at the initiation of suppressor coculture bioassays completely neutralizes the suppressive effect of suppressor T cells exerted on CD8-positive responder T cells, but does not restore expression of transferrin and interleukin-2 receptors on CD4-positive T cells. Hence, CD4-positive T cells are the direct target of the suppressor cells, while inhibition of transferrin and interleukin-2 receptor expression on CD8-positive T cells results from reduced levels of interleukin-2 in suppressor cell-regulated cultures. In suppressor cell modified mixed lymphocyte reactions supplemented with exogenous interleukin-2 CD8+/CD28- responder cells proliferate preferentially. It is apparent that mixed lymphocyte reactions supplemented with allosensitized suppressor cells cultured in an interleukin-2-rich environment create a milieu that permits the preferential expansion of T cells with suppressor effector phenotype. This in vitro system provides a convenient model in which to cultivate activated CD8+/CD28- T cells.

Higher-harmonics suppressor for soft x rays

We have developed an apparatus for suppressing higher harmonics contained in the soft x-ray output beam of grazing-incidence grating monochromators. It consists of eight pairs of total-reflection mirrors. Each pair serves as a low-pass filter with the cutoff energy different from one another. The eight pairs are designed to cover an energy range of 80–1600 eV with an efficiency of harmonic suppression better than 97%, while transmitting more than 50% of the fundamental photons. We have tested its preliminary performance on the soft x-ray beamline BL-8A at the Photon Factory. We present the observed transmission efficiencies and the effects of the harmonic suppressor on measurements of reflectivity and fluorescence spectra.

Suppression of Pisatin, Phenylalanine Ammonia-Lyase mRNA, and Chalcone Synthase mRNA Accumulation by a Putative Pathogenicity Factor from the FungusMycosphaerella pinodes

Effects of the fungal suppressor isolated from a pea pathogen, Mycosphaerella pinodes, were examined on pea defense reactions with respect to pisatin accumulation, phenylalanine ammonialyase (PAL) activity, and the corresponding PAL or chalcone synthase (CHS) mRNA level

Studies of the effect of suppressor T lymphocytes on the induction of antithyroid microsomal antibody-secreting cells in autoimmune thyroid disease.

The suppressor function in CD8 (suppressor/cytotoxic) T lymphocytes from patients with autoimmune thyroid disease and normal subjects has been studied. CD8 and CD4 (helper/inducer) cells were separated by the panning method. Patient's non-T cells and autologous CD4 cells were cultured with or without autologous or allogeneic CD8 cells in the presence of either pokeweed mitogen or Staphylococcus aureus strain Cowan 1 plus human thyroid microsomal antigen. Antithyroid microsomal antibody (AMA) and total immunoglobulin G (IgG)-secreting non-T cells were measured by enzyme-linked immunosorbent spot assay. With pokeweed mitogen stimulation, the suppressor effect of CD8 cells from patients with serum AMA on the induction of AMA (of IgG type)-secreting cells was significantly less than that of CD8 cells from normal subjects. CD8 cells from patients with no serum AMA suppressed the induction of AMA-secreting cells as much as did normal CD8 cells. CD8 cells from both patients and normal subjects suppressed the induction of IgG-secreting cells equally well. On the other hand, with the combination of S. aureus strain Cowan 1 and human thyroid microsomal antigen (1 mg/L) stimulation, CD8 cells from both normal subjects and patients only slightly suppressed the induction of IgG-secreting cells. However, under these circumstances, once again, CD8 cells from both normal subjects and patients with no serum AMA suppressed the induction of AMA-secreting cells, whereas CD8 cells from patients with serum AMA suppressed the induction of the AMA-secreting cells significantly less. Higher TMc concentrations enhanced the suppressor effect of CD8 cells from patients with serum AMA on the induction of AMA-secreting cells. Furthermore, Concanavalin A, when added to the stimuli described above, further inhibited the induction of both AMA- and IgG-secreting cells by CD8 cells from patients with serum AMA. There thus appears to be a relative defect of antigen-specific suppressor T lymphocyte function in CD8 cells from patients with autoimmune thyroid disease, which may result in the presence of autoantibody-secreting cells in those patients.

Immunologic effects of cimetidine: potential uses.

Suppressor T lymphocytes play a major regulatory role in the function of the immune system. Since the discovery of histamine (H2) receptors on the surface of these immune cells, studies have demonstrated that cimetidine diminishes the effect of suppressor T cells in both cellular- and humoral-mediated (antibody) immune reactions. Preliminary clinical results demonstrate that cimetidine has a beneficial effect on a variety of immune functions. An antineoplastic effect among tumor-bearing animals has also been found, suggesting the drug may be effective against certain human cancers, probably as an immune potentiator. Cimetidine has been used in the treatment of human cancer in combination with interferon or coumarin and as a single agent. Modest tumor response rates have been observed. The finding that cimetidine accelerates healing of herpesvirus infections is intriguing. These encouraging, albeit preliminary, results emphasize the need for additional studies on the drug's antiviral properties.

Crohn's disease. New concepts of pathogenesis and current approaches to treatment.

One theory of the pathogenesis of Crohn's disease is that rather than being caused by a unique environmental agent, it is the result of an abnormal immune response in the gastrointestinal tract. Recent studies indicate that Crohn's disease in its early stages is frequently associated with the presence of circulating antigen-non-specific suppressor T cells. Such T cells are also found in experimental inflammation caused by Chlamydia organisms in the gastrointestinal tract of nonhuman primates. Taken together, these data suggest that the suppressor T cells are markers of an underlying and persistent, antigen-specific immune response to an as yet unidentified antigen or set of antigens. We postulate that this underlying antigen-specific response is the result of a primary immunoregulatory abnormality involving an imbalance between the effects of antigen-specific helper and suppressor T cells which recognize a common antigen or antigens present in the mucosal environment.

Functional analysis of antigen-nonspecific T-cell suppression: I. Effect of mitogen-induced T suppressor cells on helper-T-cell clones

The effect of mitogen-induced nonspecific suppressor T cells (Ts) 2 2 Abbreviations used: Ts, T suppressor cell; MHC, major histocompatibility complex; TRF, T-cell replacing factor; Con A, concanavalin A; SN, supernatant; TNP, trinitrophenyl; TNP-KLH, trinitrophenylkeyhole limpet hemocyanin; rIl-2, recombinant interleukin 2; SRBC, sheep red blood cells; PFC, plaque-forming cell; Mφ, macrophage. on T-helper-cell activity was investigated using isolated clones of murine T-helper cells as targets. TNP-self-reactive Thy-1 +, Ly1 + T-cell clones were isolated after continuous culture of T cells derived from picryl chloride-sensitized mice and were characterized by their ability to proliferate in an antigen-specific and MHC-restricted manner. In addition, selected T-cell clones were found to produce both interleukin-2 (Il-2) and T-cell replacing factor (TRF), lymphokines characteristic of helper T cells. Concanavalin A (Con A)-induced Ts cells inhibited the antigen-specific proliferation of these helper-T-cell clones in a noncytotoxic manner even in the presence of exogenous Il-2. This implied that failure to proliferate was not merely due to an inability of these clones to produce Il-2. The kinetics of suppression also suggested that early T-cell activation signals were not affected. Furthermore, coculture experiments indicated that while proliferation could be severely inhibited, the actual secretion of lymphokines such as Il-2 and TRF by the T-helper clones was not. Our data suggest that nonspecific Ts modulation of proliferation versus helper factor production are under separate control in cloned T-cell populations, with lymphokine secretion remaining intact in the presence of Con A-induced Ts cells.

Kinetic analysis of lamB mutants suggests the signal sequence plays multiple roles in protein export.

We have developed a quantitative assay to measure the rate of processing of precursor LamB into mature protein and have used this assay to characterize 10 previously isolated and 3 new lamB signal sequence mutants. The data suggest that the LamB signal sequence serves a complex function. Our assay has revealed five types of signal sequence defect: 1) a strong kinetic defect resulting from alteration of the secondary structure in the putative alpha-helical region in the hydrophobic core, 2) a strong, or 3) a weak kinetic defect due to placement of a charged residue in the hydrophobic core, 4) decreased synthesis of LamB, and 5) both a decrease in synthesis and a strong kinetic defect. The effect of an extragenic suppressor, prlA4 on the rate of processing pLamB containing signal sequence mutations was also examined and compared to the rates in wild-type strains. It was found that prlA4 increases the rate of processing in some, but not all, mutants having a kinetic defect while having no effect on the decreased synthesis seen in mutants of types 4 and 5.

Non‐Specific Induction of Pisatin and Local Resistance in Pea Leaves by Elicitors from Mycosphaerella pinodes, M. melonis and M. ligulicola and the Effect of Suppressor from M. pinodes

AbstractThe accumulation of pisatin was induced non‐specifically by elicitors prepared from the high molecular weight fraction (molecular weight: more than 10,000 daltons) of the spore germination fluid of three species of Mycosphaerella‐plant pathogens in pea leaves with epidermis removed, regardless of the pathogenicity of the fungi to pea. Before the elicitation of pisatin synthesis, local resistance to infection by Mycosphaerella pinodes was induced by elicitors again non‐specifically inpea leaves in which wax had been removed from the leaf surface. The substance responsible for local resistance could be extracted with ethylacetate from the elicitor‐containing drop diffusate which was placed on pea leaves. The substance prevented the penetration of M. pinodes through heat‐killed pea epidermis, but did not affect spore germination. The suppressor prepared from the low molecular weight fraction (molecular weight: less than 10,000 daltons) of the spore germination fluid of M.pinodes counteracted the ability of elicitors to induce both phases of resistance mechanisms.

Effect of antigen-induced suppressor B cells on development of memory B cells, carrier-specific helper T cells, and antibody-forming cells

This paper studies the presence of an Fc receptor on the surface of antigen-induced suppressor B cells (AISB), their sensitivity to antiproliferative agents, their interaction with other immunoregulator cells and with the precursors of antibody-forming cells (AFC). Mice were used in the experiments and were irradiated in a dose of 8.5 Gy (/sup 137/Cs). The effect of AISB on memory B cells is shown as is the effect of AISB on development of carrier-specific helper T cells. Also presented is the effect of AISB on development of AFC.