Surface characterization of microtextured silicone

A set of microtextured silicone surfaces was manufactured using the technique of photolithography. The textures consist of a uniform array that imparts anisotropy to the surfaces. Processing the material required multiple steps which may have altered the surface characteristics. This project aimed to determine if a surface texture on implant grade silicone would affect the material characteristics. ESCA and contact angle studies revealed no measurable alteration of the surface chemistry or surface energy due to the texturing procedure or the presence of the texture. Both analytical techniques confirmed the material was silicone. The actual dimensions of the surface textures, size, spacing, depth and orientation of the textures were found to be close to the design values, using SEM and quantitative two- and three-dimensional profilometry. Standard 2D profilometry was not sufficient to characterize the surfaces, as a direct result of the uniformity of the arrays. A method of characterizing regular surface periodic structures is presented.

Determination of three-dimensional morphometry of adherent cells by surface profilometry

A three-dimensional, non-contacting surface profiler was used to analyse cells that had been previously prepared for scanning electron microscopy. The height of ten attached and spread cells was measured in both two- and three-dimensions (2-D and 3-D). The 2-D scan is a typical, linear profilometer output, while a 3-D image is produced with a 3-D detector. The 3-D contour plots of each cell were then compared with scanning electron microscopy micrographs by digitizing four morphological parameters: perimeter, surface area, long axis and short axis of each cell. A paired Student's t test showed that the two imaging techniques are not equivalent. Non-equivalence was attributed to a difference in the method of calibration. However, when combined with scanning electron microscopy, the profiler allowed complete three-dimensional quantitative analysis of cellular morphology.

Comparison of the effects of FK-506, cyclosporin A and rapamycin on IL-2 production

The immunosuppressive compounds FK-506, cyclosporin A (CsA) and rapamycin inhibit both the human and mouse mixed lymphocyte reactions (MLR) with IC50s of 2-5 x 10(-10) M for FK-506 and rapamycin and 10(-8) M for CsA. FK-506 and CsA were also potent inhibitors of A23187/PMA-stimulated IL-2 production by Jurkat and HuT-78 cells but had no effect on the response of mouse CTLL cells to IL-2. IC50 values for inhibition of IL-2 production closely matched those for inhibition of the MLR and both drugs were active only during the first 4-6 hr following stimulation. In contrast, rapamycin was a poor inhibitor of IL-2 production, although it inhibited cellular responses to IL-2. The IC50 values for these two activities indicated that neither alone accounted for rapamycin inhibition of the MLR. FK-506 and CsA affected IL-2 gene transcription in Jurkat cells by the same mechanism. Both inhibited the appearance of the transcription factor, NFAT, whereas rapamycin did not. The appearance of another transcription factor, NFK beta, was unaffected by all three drugs. The effects of FK-506 and CsA on IL-2 gene expression, therefore, are similar even though the two drugs act through distinct cytosolic receptors.

Texturing of polymer surfaces at the cellular level

A technique to surface-texture polymer sheets with any conceivable surface morphology is described. It uses technology developed for semiconductor device fabrication. It allows the definition and control of implant surface texture at subcellular levels, down to 2 micron dimensions, and the cellular response to those textures to be studied in vitro and in vivo. The results of a pilot study are presented and the biological significance of a microscopic surface texture is discussed.

The processing of interleukin-1 beta studied with antibodies raised against synthetic peptides from the precursor N-terminal region

The exact sequence of events during processing of human interleukin-1 beta (IL-1 beta) and the fate of the N-terminal region are unknown. We have used anti-peptide sera specific for the precursor and mature regions of IL-1 beta to study biosynthesis. These were raised against peptides corresponding to amino acids 1-15, 17-32, and 43-54 of the precursor and a peptide corresponding to the C-terminal 33 amino acids of mature human IL-1 beta. Antiserum to the mature region peptide immunoprecipitated the 35-kD precursor from cell lysates and 17-kD mature IL-1 beta and a 31-kD protein from the culture supernatants from radiolabeled human peripheral blood monocytes stimulated with lipopolysaccharide (LPS). Antisera to peptides from the precursor region also immunoprecipitated the 35-kD IL-1 beta precursor but not the 31-kD or 17-kD forms. Of the precursor-specific sera, only antiserum to amino acids 1-15 specifically recognized any other proteins; a peptide of 18 kD and a low molecular weight peptide, both of which accumulated in the medium. The 18-kD protein was not recognized by any of the other antisera and is unlikely to be the N-terminal region of the precursor removed during processing. Pulse-chase experiments indicated that the 31-kD protein could be a processing intermediate and also that it was itself an end product along with full-length precursor. Only 17-kD mature IL-1 beta had biological activity.

The volume conductor effects of anisotropic muscle on body surface potentials using an eccentric spheres model

The purpose of this paper is to determine the volume conductor effects of muscle anisotropy on body surface potentials using an eccentric spheres model with a uniform double layer source configuration. Previous eccentric spheres work assumed that cardiac muscle anisotropy was small and that skeletal muscle effects could be accounted for by boundary extension, i.e., by scaling the conductivities and dimensions. However, in this paper, anisotropy for both the myocardium and the skeletal muscle is explicitly incorporated into the eccentric spheres volume conductor model. The anisotropy is treated as having uniform orthogonal components in the radial and tangential directions for both the skeletal muscle and myocardium. The solution for Laplace's equation is written in a series expansion of appropriate basis functions for each region. In the isotropic regions spherical harmonics with integer radial dependence and Legendre polynomial azimuthal dependence are utilized. For the anisotropic regions, Legendre polynomials are still appropriate for the azimuthal dependence, but noninteger powers of radial dependence are required. The approximate representation for anisotropy, i.e., the boundary extension method for the skeletal muscle and a scaled homogeneous conductivity without boundary extension for the myocardium are compared with explicit representations for the two regions. Two basic conclusions are drawn from the results. First, the treatment of skeletal muscle anisotropy by the boundary extension method is a valid and useful simplification which yields errors of 2% for the peak body surface potential. The second conclusion drawn from this study is that myocardial anisotropy has a significant effect on the magnitude of body surface potentials.(ABSTRACT TRUNCATED AT 250 WORDS)

A repetitive peptide of Leishmania can activate T helper type 2 cells and enhance disease progression

Leishmaniasis provides a biologically relevant model to analyze the heterogeneity of CD4+ T cells and may lead to answering the major question of the mechanism for the preferential induction of T helper type 1 (Th1) and Th2 cells. Using synthetic peptides corresponding to the tandemly repeating regions of Leishmania proteins, we have identified an epitope that can preferentially induce the disease-exacerbating Th2 cells in susceptible BALB/c mice. Lymph node cells from BALB/c mice immunized subcutaneously with the octamer (p183) of the repeating 10-mer peptide EAEEAARLQA proliferated strongly against the peptide as well as the soluble antigen extract (SolAg) of Leishmania major. The proliferative T cells are CD4+, major histocompatibility complex class II restricted, and secrete interleukin 4 (IL-4) but little or no IL-2 and interferon gamma when stimulated with the peptide in vitro. T cells from BALB/c mice with progressive disease, but not from BALB/c mice cured of the infection, recognized this epitope. BALB/c mice injected subcutaneously with p183 developed significantly exacerbated disease when subsequently challenged with L. major. Furthermore, subcutaneous injection with p183 prevented the subsequent induction of resistance against L. major by intravenous immunization with soluble antigen. The T cell response to p183 is H-2d restricted. Immunization of the genetically resistant B10.D2 mice with p183 also produced strong T cell responses and exacerbated disease when challenged with L. major.

IL-1 binds to high affinity receptors on human osteosarcoma cells and potentiates prostaglandin E2 stimulation of cAMP production

IL-1 is a potent bone resorbing agent. Its mechanism of action is unknown, but the presence of osteoblasts was shown to be necessary for IL-1 stimulation of bone resorption by isolated osteoclasts. This study examines the presence of IL-1R and IL-1 effects in osteoblastic cells from a clonal human osteosarcoma cell line, Saos-2/B-10. We found that the binding affinity and the number of binding sites increases substantially during the postconfluent stage. Scatchard and curve-fitting analysis revealed one class of high affinity binding sites, with Kd/Ki's of 40 +/- 17 pM (mean +/- SD) for IL-1 alpha (n = 5) and 9 +/- 7 pM for IL-1 beta (n = 5) and 2916 +/- 2438 (n = 6) receptors/cell. Incubation of the cells with 125I-IL-1 alpha (100 pM) at 4 degrees C, followed by incubation at 37 degrees C up to 4 h, revealed internalization of receptor-bound IL-1 alpha. Chemical cross-linking studies showed that the IL-1R in Saos-2/B-10 cells had a molecular mass of approximately 80 kDa. To assess the biologic effect of IL-1 in Saos-2/B-10 cells, we determined PGE2 content and adenylate cyclase activity. Although IL-1 had no effect on PGE2 synthesis, both IL-1 alpha and IL-1 beta enhanced PGE2 stimulation of adenylate cyclase two- to four-fold in a dose-dependent manner. The half-maximal effect for IL-1 alpha was seen at 8 to 10 pM and for IL-1 beta at 0.6 to 1.8 pM. IL-1 did not enhance basal adenylate cyclase or stimulation by parathyroid hormone, isoproterenol, or forskolin. IL-1 enhancement of PGE2-stimulated adenylate cyclase was detected between 1 to 2 h, was maximal at 4 to 5 h, was not prevented by cycloheximide treatment, and was seen in membranes from IL-1 pretreated cells. These data show effects of IL-1 on a human osteoblast-like cell line that are mediated by high affinity receptors. These IL-1 effects could contribute to the biologic action of IL-1 on bone.

IL-1 binds to high affinity receptors on human osteosarcoma cells and potentiates prostaglandin E2 stimulation of cAMP production

IL-1 is a potent bone resorbing agent. Its mechanism of action is unknown, but the presence of osteoblasts was shown to be necessary for IL-1 stimulation of bone resorption by isolated osteoclasts. This study examines the presence of IL-1R and IL-1 effects in osteoblastic cells from a clonal human osteosarcoma cell line, Saos-2/B-10. We found that the binding affinity and the number of binding sites increases substantially during the postconfluent stage. Scatchard and curve-fitting analysis revealed one class of high affinity binding sites, with Kd/Ki's of 40 +/- 17 pM (mean +/- SD) for IL-1 alpha (n = 5) and 9 +/- 7 pM for IL-1 beta (n = 5) and 2916 +/- 2438 (n = 6) receptors/cell. Incubation of the cells with 125I-IL-1 alpha (100 pM) at 4 degrees C, followed by incubation at 37 degrees C up to 4 h, revealed internalization of receptor-bound IL-1 alpha. Chemical cross-linking studies showed that the IL-1R in Saos-2/B-10 cells had a molecular mass of approximately 80 kDa. To assess the biologic effect of IL-1 in Saos-2/B-10 cells, we determined PGE2 content and adenylate cyclase activity. Although IL-1 had no effect on PGE2 synthesis, both IL-1 alpha and IL-1 beta enhanced PGE2 stimulation of adenylate cyclase two- to four-fold in a dose-dependent manner. The half-maximal effect for IL-1 alpha was seen at 8 to 10 pM and for IL-1 beta at 0.6 to 1.8 pM. IL-1 did not enhance basal adenylate cyclase or stimulation by parathyroid hormone, isoproterenol, or forskolin. IL-1 enhancement of PGE2-stimulated adenylate cyclase was detected between 1 to 2 h, was maximal at 4 to 5 h, was not prevented by cycloheximide treatment, and was seen in membranes from IL-1 pretreated cells. These data show effects of IL-1 on a human osteoblast-like cell line that are mediated by high affinity receptors. These IL-1 effects could contribute to the biologic action of IL-1 on bone.

Transcutaneous measurement of oxygen and carbon dioxide tension (TcPO2 and TcPCO2) during treadmill exercise in patients with arterial occlusive disease (AOD)--stages I and II

Transcutaneous oxygen and carbon dioxide tensions were measured during treadmill exercise in 30 patients with stages I and II arterial occlusive disease and 28 normal controls. Measuring sites were the dorsum of the foot and the frontal thorax. The calculated oxygen index at maximum exercise/rest (foot/thorax) differentiated with 100% sensitivity and specifity between the two groups. The oxygen index was the only parameter with a significant positive correlation with the pain-free walking distance, whereas, eg, oscillography and Doppler analysis did not correlate. Carbon dioxide tensions showed significant differences only in the recovery time between patients and normal controls.

Ultrastructural localization of interleukin 1 in human peripheral blood monocytes; evidence for IL-1 beta in mitochondria

The pathway of interleukin 1 (IL-1) secretion from the cell remains unclear. IL-1 beta is the major form produced by human monocytes, and is synthesized as a precursor of 35 kDa which is processed to the extracellular biologically active 17 kDa form. We have examined the intracellular localization of IL-1 beta in lipopolysaccharide (LPS)-stimulated human peripheral blood monocytes, by immunocytochemistry and immunoprecipitation of subcellular fractions. LPS treatment slightly damaged the cells. Unstimulated cells showed very little immunolabelling. In contrast, there was heavy immunolabelling on LPS stimulated cells. Immunolabelling occurred within the cytoplasm, nucleus and mitochondria. There was no immunolabelling on the membranous secretory organelles and the plasma membrane. Blebs of cytoplasm budding from the cell surface were immunolabeled, suggesting an alternative route of secretion of IL-1 beta from the cell. Immunoprecipitation studies confirmed these results.

[Central pontine myelinolysis following severe hyponatremia]

Central pontine myelinolysis is a process of demyelinisation with variable neurological symptoms related to the localization. Predisposing factors are alcoholism and malnutrition. Rapid correction of severe hyponatremia is suspected to be a primary cause for central pontine myelinolysis. We report a 43 year old chronic alcoholic and polytoxicomanic female patient, who was admitted comatose with a serum sodium level of 94 mmol/l, caused by a syndrome of inappropriate ADH secretion. After initial improvement under careful sodium correction, the patients neurologic condition degraded progressively and within 4 weeks she developed a "locked-in"-syndrome. Only then the suspected central pontine myelinolysis could be demonstrated in nuclear magnetic resonance and computer tomography. We presume that, although sodium correction was done relatively slowly in this patient, it probably contributed to her development of central pontine myelinolysis all the same. Due to this case we review the literature on correction of hyponatremia, which shows growing evidence that it should start early but be continued very slowly (rise in serum-Na: max. 0.6 mmol/l/h) and requires frequent laboratory controls.

3-Deazaadenosine--an inhibitor of interleukin 1 production by human peripheral blood monocytes

3-Deazaadenosine (c3Ado) has been reported to have properties of an immunosuppressive and anti-inflammatory agent. This study was designed to investigate whether c3Ado might exert anti-inflammatory activities through inhibiting Interleukin 1 (IL-1). c3Ado was found to be a potent inhibitor of IL-1 production by LPS stimulated human peripheral blood monocytes and acted at the level of synthesis rather than secretion. c3Ado also had direct effects on IL-1 biological activity in two separate assays; thymocyte proliferation and induction of prostaglandin release. Further experiments indicated that c3Ado also inhibited growth factor dependent proliferation driven by both Interleukin-2 and Interleukin-3 as well as the proliferation of a number of non-growth factor dependent cells. However, short term exposure to c3Ado resulted in no inhibition of 3H-thymidine incorporation by cells but a significant inhibition of 3H-uridine uptake into TCA precipitable material. These results suggest that c3Ado is a selective inhibitor of RNA synthesis and inhibits IL-1 production and activity by blocking new messenger RNA production induced by LPS or IL-1. General inhibition of RNA synthesis would also account for its anti-proliferative activity.

Transient response of rod outer segment cGMP phosphodiesterase to actinic light pulses. II. Detailed quantitative kinetic model

In the accompanying article (Schmidt, J.A., and Yguerabide, J. (1989) J. Biol. Chem. 264, 19790-19803), we presented a minimal quantitative kinetic model with one rate-limiting step for the transient response of rod outer segment (ROS) phosphodiesterase (PDE) to stimulating light pulses of low fractional bleach (linear response range) and showed that the model was in excellent quantitative agreement with experimental results. The model characterizes the PDE response in terms of the specific rate constant of the rate-limiting step, kL, the lifetime of photoactivated rhodopsin, tau R, and the lifetime of activated PDE, tau P, but makes no predictions on how these kinetic parameters should depend on the concentrations of the various reactive species involved in the PDE response to light and does not reveal the nature of the rate-limiting step. However, we established by curve fitting experimental data to theoretical expressions from the model that kL increases hyperbolically with [GTP], tau R decreases with [GTP], and tau P is independent of GTP. In this report we present three detailed kinetic models which make specific quantitative predictions on how the kinetic parameters of the minimal model should depend on nucleotide and G protein concentrations and test the models against experimental data. Each model consists of one rate-limiting step. The first detailed model postulates that the rate-limiting step is the dissociation of R*GT into R* and GT (T stands for GTP). The second model postulates that the rate-limiting step is the binding of GTP to R*G, and the third model postulates that the rate-limiting step is the encounter rate of R* and G on the ROS disc membrane. We find that only the first detailed model is consistent with the experimental results as characterized by the minimal model. Using this detailed model we (a) define kL and tau R in terms of more fundamental equilibrium and rate parameters, (b) develop a theory for the systematic evaluation of amplification or gain of the PDE light response from light-stimulated GTP-binding data as well as v(t) versus t graphs, and (c) clarify methods which have been used in the past to evaluate gain experimentally.

Transient response of retinal rod outer segment phosphodiesterase to actinic light pulses. I. Simple quantitative kinetic model

We present a quantitative kinetic model for the transient velocity (microM of cGMP hydrolyzed/s) response of retinal rod outer segment (ROS) cGMP phosphodiesterase (v(t) versus t) to a stimulating light pulse in the linear response range. The model gives an excellent fit to experimental v(t) versus t data for ROS suspensions at different concentrations of GTP and GDP and clarifies experimental results which are difficult to understand in the absence of such a model. It contains the minimum number of steps required to fit our experimental data and consists of one rate-limiting step with specific rate kL for the production of active phosphodiesterase (PDE), PDE*, by photoactivated rhodopsin, R*, and deactivation processes for R* and PDE* with lifetimes tau R and tau P, respectively. The experimental graphs of v(t) versus t at each concentration of GTP and GDP are characterized by a fast rise to a peak value, vpeak, followed by a slow decay to zero level. The minimal kinetic model allows us to characterized completely the effects of GTP and GDP, and any other pertinent species, in terms of their effects on the parameters kL, tau R, and tau P. Our kinetic model indicates that for "washed" ROS preparations (a) the risetime of v(t) is determined by tau P which has a value of about 2 s and is insensitive to [GTP]. (b) The decay of v(t) is determined by tau R which decreases with [GTP] and has a value greater than 300 s at low [GTP] and a limiting value of 50 s at high [GTP]. We attribute the greater than 300 s lifetime to the complex R*G (where G is ROS G protein) and the 50-s lifetime to free R*. (c) The rate kL increases hyperbolically with [GTP] with a half-maximal value of 56 microM and kL.max = 22-45 s-1. (d) Peak velocity is given by the expression vpeak alpha kL tau P which is consistent with the dependence of kL on [GTP] and the experimental finding that vpeak varies hyperbolically with [GTP]. The minimal model has also allowed us to (a) develop clear definitions of amplification for the light-triggered enzymatic cascade and (b) clarify experimental methods for measuring gain.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of a monocyte specific pre-interleukin 1 beta convertase activity

Interleukin 1 (IL-1) is a lymphokine secreted by monocytes in response to a variety of inflammatory stimuli. IL-1 beta, the predominant form of IL-1 produced by human monocytes, is synthesized as an inactive precursor of 31 kDa and is cleaved at Asp116-Ala117 to yield a 17.5-kDa extracellular form. The exact cellular site of cleavage and mechanism of secretion is at present unknown. We have prepared cell-free postnuclear extracts from freshly isolated human monocytes as well as THP.1 cells, a human monocyte-like cell line, and various blood lymphocytes and fibroblast cell lines. Using pre-IL-1 beta synthesized by in vitro transcription and translation, we have shown that only extracts derived from human monocytes and THP.1 cells were capable of cleaving precursor IL-1 beta to authentic mature IL-1 beta. Subcellular fractionation of the extracts suggested that the processing activity is found in the cytosol of monocytes or monocyte-like cell lines. The cleavage product of this protease is identical to authentic IL-1 beta as shown by mobility on SDS/PAGE and amino acid sequence analysis of the [3H]leucine-labeled product. The cleavage product is also capable of binding to the IL-1 receptor found on fibroblast membranes. Finally, mutation of Asp116----Ala116 rendered the IL-1 beta precursor resistant to cleavage by the processing activity. We conclude that a protease activity found only in monocytes will specifically process IL-1 beta to an active form.

Peritoneal oxygenation of normoxic and hypoxic dogs

The ability of an oxygen saturated fluorocarbon, perfluorodecalin (C10F18), to raise the arterial partial pressure of oxygen (PaO2) of anesthetized dogs, was tested by peritoneal lavage in normoxic and hypoxic animals. While breathing room air, five of six animals showed an increased PaO2 of 5-10 torr above reference values. In cases of mild hypoxia, increases of 5-25 torr were observed. No increase in PaO2 was seen when hypoxia was severe. A mathematical model was used to analyze the data and determine a transport coefficient (k). Calculated k values were 1.18 +/- 0.151 ml O2 STPD per minute for normoxic animals and 0.91 +/- 0.180 ml O2 STPD per minute for hypoxic animals, respectively. The estimated transport coefficients are small and indicate that physiologically significant amounts of O2 cannot be delivered by the proposed method under the experimental conditions used. The low k values were attributed to long diffusion distances and small effective surface areas in the abdominal cavity.

Role of interleukin 1 in the activation of T lymphocytes

The activation of T lymphocytes requires their stimulation via clonotypic antigen receptors as well as nonantigen-specific costimulators, the best defined of which is the cytokine interleukin 1 (IL-1). Recent studies have shown that murine CD4+ helper T lymphocytes consist of two nonoverlapping subsets that selectively utilize interleukin 2 (IL-2) or interleukin 4 as their autocrine growth factors and are called Th1 and Th2 cells, respectively. We now show that IL-1 functions as a costimulator for the proliferation of Th2 but not of Th1 clones and only Th2 cells express high-affinity receptors for IL-1. Secretion of autocrine growth-promoting lymphokines by Th1 and Th2 cells occurs after stimulation via the antigen receptor-CD3 complex and is neither dependent on nor affected by IL-1. These findings suggest that the activation of T lymphocytes can be divided into two stages, lymphokine secretion and proliferation, and only proliferation requires costimulators such as IL-1. Moreover, the prevailing view that IL-1 functions as a costimulator by inducing secretion of IL-2 or expression of IL-2 receptors may not be generally applicable, because IL-2-producing Th1 clones do not express receptors for IL-1 and are insensitive to this cytokine.

Down-regulation of IL-1 beta biosynthesis by inducers of the heat-shock response

The effect of heat on IL-1 beta biosynthesis was investigated in both THP-1 cells, a myelomonocytic cell line which can be induced to make IL-1 alpha and beta, and human peripheral blood adherent monocytes (PBMC). Induction of THP-1 cells with LPS at 39 to 41 degrees C for 2 to 4 h resulted in the expected increased synthesis of the heat-shock proteins hsp 70 and hsp 90 but decreased synthesis of the IL-1 beta precursor protein, p35 (and its mRNA), compared with control cells at 37 degrees C. This appeared to be a direct effect on p35 synthesis rather than a block in LPS induction because heat also acted on preinduced cells. PBMC similarly incubated for 4 h with LPS required a temperature of 41 to 42 degrees C to induce hsp and show a decrease in p35 synthesis. Chemical inducers of the heat-shock response (heavy metals, sulphydryl reagents) were also effective inhibitors of IL-1 beta biosynthesis. A correlation was seen between the extent of IL-1 beta reduction and the level of hsp induction by chemical inducers in both THP-1 cells and PBMC which suggests that the two responses are linked. In addition, a gold salt currently used for therapy of chronic inflammation, auranofin, induced hsp and inhibited IL-1 beta biosynthesis, whereas a second salt, sodium aurothiomalate, did neither. These results support the hypothesis that elevated temperature is one of the physiologic signals for down-regulation of IL-1 beta biosynthesis through a mechanism related to the induction of hsp.

Down-regulation of IL-1 beta biosynthesis by inducers of the heat-shock response

The effect of heat on IL-1 beta biosynthesis was investigated in both THP-1 cells, a myelomonocytic cell line which can be induced to make IL-1 alpha and beta, and human peripheral blood adherent monocytes (PBMC). Induction of THP-1 cells with LPS at 39 to 41 degrees C for 2 to 4 h resulted in the expected increased synthesis of the heat-shock proteins hsp 70 and hsp 90 but decreased synthesis of the IL-1 beta precursor protein, p35 (and its mRNA), compared with control cells at 37 degrees C. This appeared to be a direct effect on p35 synthesis rather than a block in LPS induction because heat also acted on preinduced cells. PBMC similarly incubated for 4 h with LPS required a temperature of 41 to 42 degrees C to induce hsp and show a decrease in p35 synthesis. Chemical inducers of the heat-shock response (heavy metals, sulphydryl reagents) were also effective inhibitors of IL-1 beta biosynthesis. A correlation was seen between the extent of IL-1 beta reduction and the level of hsp induction by chemical inducers in both THP-1 cells and PBMC which suggests that the two responses are linked. In addition, a gold salt currently used for therapy of chronic inflammation, auranofin, induced hsp and inhibited IL-1 beta biosynthesis, whereas a second salt, sodium aurothiomalate, did neither. These results support the hypothesis that elevated temperature is one of the physiologic signals for down-regulation of IL-1 beta biosynthesis through a mechanism related to the induction of hsp.

Suppressive substance produced by T cells from mice chronically infected with Trypanosoma cruzi. III. Genetic restriction and further characterization

Earlier papers in this series reported that the culture supernatant of splenic L3T4+, Lyt-2- T cells from susceptible CBA mice chronically infected with Trypanosoma cruzi contain a SS3 that can inhibit the induction of delayed-type hypersensitivity to a wide range of Ag. The SS is a glycoprotein with an apparent molecular mass of 30 to 60 kDa and is distinct from T. cruzi Ag, IL-1, IL-2, IL-3 or IFN-gamma. It also has no effect on Th cells for antibody, cytotoxic T cells or immediate-type hypersensitivity. In this paper, we report that SS can suppress the induction of proliferating T cells but not the presentation of Ag to a cloned T cell line (D10). It also has no effect on the induction of delayed-type hypersensitivity in vitro. SS is produced by a number of inbred mouse strains irrespective of their susceptibility to infection with T. cruzi (BALB/c, highly susceptible; CBA, susceptible; C57BL/10, resistant) but only CBA mice are sensitive to the suppressive action of SS. This is so whether the SS is derived from CBA, BALB/c, or C57BL/10. The sensitivity to SS is not a feature of the H-2k haplotype inasmuch as B10.BR and BALB/k mice (also H-2k) do not respond to SS. Attempts to purify SS with a range of biochemical techniques substantially enriched the specific activity but failed to produce a substance visualizable by analytical gel electrophoresis. IEF chromatography revealed SS activity spanning a pH range from 6 to less than 4. This suggests that SS is likely to be a minor heterogeneous component of the suppressive supernatant. The genetically highly restricted nature of its action is intriguing and may explain some of the contradictory reports in the literature on this subject.

Identification of a high-affinity receptor for interleukin 1 alpha and interleukin 1 beta on cultured human rheumatoid synovial cells

In this report the binding of recombinant human interleukins 1 alpha and 1 beta (rIL-1 alpha and rIL-1 beta) to primary cultures of human rheumatoid synovial cells is measured and compared to the concentrations of these mediators required for stimulation of PGE2 production by these same cells. The average concentration of IL-1 alpha required for half-maximal stimulation of PGE2 was 4.6 +/- 1.5 pM (+/- SEM) (n = 6), whereas for IL-1 beta half-maximal stimulation was observed at a concentration of 1.3 +/- 0.24 pM (n = 6). Both direct and competitive binding experiments were performed. In direct binding experiments, IL-1 alpha bound with a Kd of 66 pM (n = 1), while IL-1 beta bound with a Kd of 4 pM (n = 2). In competitive binding experiments, IL-1 alpha inhibited binding of 125I-IL-1 alpha with a Ki of 33-36 pM (n = 2) and binding of 125I-IL-1 beta with a Ki of 51-63 pM (n = 2). IL-1 beta inhibited binding of 125I-IL-1 alpha with a Ki of 2-3 pM (n = 2) and binding of 125I-IL-1 beta with a Ki of 7 pM (n = 2). The binding data were best fit by a model specifying a single class of receptors with homogeneous affinity for either IL-1 alpha or IL-1 beta and with an abundance of 3,000-14,000 sites per cell. Autoradiography showed that the vast majority of the synoviocytes within the cultures possessed IL-1 receptors. Comparison of biological response curves with the binding curves indicates that the observed receptors exhibit sufficiently high affinity to mediate the response of human synoviocytes to low picomolar concentrations of IL-1 alpha and IL-1 beta.

Suppressive substance produced by T cells from mice chronically infected with Trypanosoma cruzi. III. Genetic restriction and further characterization

Earlier papers in this series reported that the culture supernatant of splenic L3T4+, Lyt-2- T cells from susceptible CBA mice chronically infected with Trypanosoma cruzi contain a SS3 that can inhibit the induction of delayed-type hypersensitivity to a wide range of Ag. The SS is a glycoprotein with an apparent molecular mass of 30 to 60 kDa and is distinct from T. cruzi Ag, IL-1, IL-2, IL-3 or IFN-gamma. It also has no effect on Th cells for antibody, cytotoxic T cells or immediate-type hypersensitivity. In this paper, we report that SS can suppress the induction of proliferating T cells but not the presentation of Ag to a cloned T cell line (D10). It also has no effect on the induction of delayed-type hypersensitivity in vitro. SS is produced by a number of inbred mouse strains irrespective of their susceptibility to infection with T. cruzi (BALB/c, highly susceptible; CBA, susceptible; C57BL/10, resistant) but only CBA mice are sensitive to the suppressive action of SS. This is so whether the SS is derived from CBA, BALB/c, or C57BL/10. The sensitivity to SS is not a feature of the H-2k haplotype inasmuch as B10.BR and BALB/k mice (also H-2k) do not respond to SS. Attempts to purify SS with a range of biochemical techniques substantially enriched the specific activity but failed to produce a substance visualizable by analytical gel electrophoresis. IEF chromatography revealed SS activity spanning a pH range from 6 to less than 4. This suggests that SS is likely to be a minor heterogeneous component of the suppressive supernatant. The genetically highly restricted nature of its action is intriguing and may explain some of the contradictory reports in the literature on this subject.

Transforming growth factor-beta is a potent immunosuppressive agent that inhibits IL-1-dependent lymphocyte proliferation

Transforming growth factor-beta (TGF-beta), a product of neoplastic and hemopoietic cells, is a bifunctional regulator of the immune response. At femtomolar concentrations, TGF-beta stimulates monocyte migration, and picomolar quantities induce synthesis of monocyte growth factors, including IL-1, that may promote tissue repair by regulating fibrosis and angiogenesis. Paradoxically, TGF-beta at picomolar concentrations also blocks the ability of IL-1 to stimulate lymphocyte proliferation. At 0.01 to 1.0 ng/ml, TGF-beta 1 and its homologue, TGF-beta 2, suppress the IL-1-dependent murine thymocyte proliferation assay. TGF-beta also inhibits human peripheral blood T lymphocyte mitogenesis. Inhibition of cell division appears to occur after activation of the lymphocytes inasmuch as neither gene expression nor translation of IL-2R is suppressed. Furthermore, TGF-beta does not block synthesis of IL-2. Therefore, TGF-beta 1 and TGF-beta 2 likely act at a site distal to IL-1 to block lymphocyte DNA synthesis. These findings suggest that TGF-beta secreted in an inflammatory site may be beneficial in diminishing lymphocyte function while promoting fibrosis and tissue repair. However, TGF-beta generated by neoplastic tissues may provide a mechanism for unrestricted tumor cell growth through its selective immunosuppressive effects.