Search PubMed⌕ Search

Biomedical subjects

R Snyderman

Publications and source records attributed to R Snyderman.

At least 127 records · Page 7Linked to original sources
PubMed1984

A potential second messenger role for unsaturated fatty acids: activation of Ca2+-dependent protein kinase.

Arachidonate and other unsaturated long-chain fatty acids were found to activate protein kinase C from human neutrophils. Kinase activation by arachidonate required calcium and was enhanced by diolein but did not require exogenous phosphatidylserine. Submaximal levels of arachidonate also enhanced the affinity of the kinase for calcium during activation by phosphatidylserine. Thus the release of arachidonate, which is triggered in many cell types by ligand-receptor interactions, could play a second messenger role in the regulation of cellular function by activation of protein kinase C.

Arachidonic Acid↗
PubMed1984

The NADPH oxidase of human polymorphonuclear leukocytes. Evidence for regulation by multiple signals.

Activation of the membrane-bound NADPH oxidase in human polymorphonuclear leukocytes can be triggered by chemoattractants, the tumor promoter phorbol myristate acetate or the calcium ionophore A23187. We have shown previously that these stimuli have markedly different temporal patterns of oxidase activation (McPhail, L. C., and Snyderman, R. (1983) J. Clin. Invest. 72, 192-200), suggesting that each follows, at least in part, a unique transductional pathway. We now report that if leukocytes were sequentially exposed to any of several combinations of heterologous stimuli, the pattern of activation by the second stimulus was strikingly altered, resulting in a more rapid rate and enhanced level of oxidase activation by the second stimulus. This suggests that exposure of cells to the first stimulus (priming) had influenced an intermediate also used by the second stimulus. The signal for priming could be clearly distinguished from the signal causing oxidase activation by the dose-response curves for each, as well as by the use of several pharmacologic agents. In addition, if leukocytes were given sequential doses of homologous stimuli, either partial (phorbol myristate acetate) or full (N-formyl-methionyl-leucyl -phenylalanine and A23187) desensitization of oxidase activation was observed. These results demonstrate that these stimuli share a common intermediate in the pathway of oxidase activation. Moreover, the data indicate that NADPH oxidase activation is regulated by at least three distinct signals: signal 1 (priming), signal 2 (activation), and signal 3 (inactivation). It is likely that more than one intracellular messenger exerts a modulating influence on NADPH oxidase activity and that its regulation involves the interplay between several cellular control proteins.

Calcimycin↗
PubMed1984

Human malignant and mitogen-transformed cells contain retroviral P15E-related antigen.

Virus-related oncogenes have been demonstrated in human tumor cells and may play a role in neoplastic transformation. Cancerous effusions contain inhibitors of monocyte function and are absorbed by monoclonal antibodies to the immunosuppressive retroviral structural protein, P15E. We therefore examined eight human malignant cell lines for P15E-related antigens, by indirect immunofluorescence. Up to 87% of fixed malignant cells were reactive with two different monoclonal anti-P15E antibodies, while under identical conditions approximately 7% of freshly isolated human mononuclear cells were positive. Differentiation of two tumor cell lines with dibutyryl cyclic AMP resulted in decreased anti-P15E reactivity. Blast transformation of human mononuclear cells with mitogens induced reactivity with anti-P15E. Thus human malignant and blast-transformed cells contain antigens related to P15E. Expression of this viral-related gene may occur during rapid cell division and be abnormally regulated in cancer cells, thus rendering them more resistant to immune destruction.

Animals↗
PubMed1984

Transductional mechanisms of chemoattractant receptors on leukocytes.

Phagocytic leukocytes contain receptors for chemoattractants on their cell surface. Binding of chemotactic factors to these receptors initiates a number of coordinated cellular responses in a strict dose-dependent manner. Motility-related functions such as shape change, cytoskeletal rearrangement, and chemotaxis are stimulated by relatively low doses of chemoattractants, while microbiocidal or cytotoxic functions (i.e., secretion of lysosomal enzymes or stimulation of the respiratory burst), require approximately 10- to 50-fold higher concentrations of these agents. The receptor for oligopeptide chemotactic factors on leukocytes has provided an important model for the study of stimulus-response coupling in phagocytic cells. This receptor on human polymorphonuclear leukocytes exists in two affinity states that are partially interconvertible. Guanine nucleotides regulate the convertibility between a portion of the high- and low-affinity states, thereby suggesting that a nucleotide regulatory protein allosterically modifies receptor affinity and participates in its transduction mechanisms. A fraction of the high-affinity receptors in PMN membranes is not subject to guanine nucleotide regulation and appears to be formed by prior exposure of the receptors to specific agonists. This high-affinity form of the oligopeptide chemoattractant receptor is rapidly internalized at 37 degrees C, and its formation may be dependent on aggregation or covalent modification of the receptor. The chemotaxis and microbiocidal functions of PMNs can be divergently manipulated by pharmacological agents indicating that the transduction mechanisms for these two types of processes are independently regulated. Aliphatic alcohols at doses that induce mild fluidization of PMN membranes increase the average affinity of the chemoattractant receptor and enhance chemotactic functions but markedly depress lysosomal enzyme secretion and the respiratory burst. In contrast, polyene antibiotics that bind to membrane cholesterol lower the receptor's affinity and depress chemotactic functions but enhance secretion of specific granule enzymes. In addition, transmethylation reactions mediated by S-adenosyl-methionine appear to regulate receptor affinity. When such reactions are blocked pharmacologically, the oligopeptide receptor on macrophages reverts to a lower average affinity form and is ineffective in transducing chemotactic as well as microbicidal functions.(ABSTRACT TRUNCATED AT 400 WORDS)

Amphotericin B↗
PubMed1984

A chemoattractant receptor on macrophages exists in two affinity states regulated by guanine nucleotides.

The binding characteristics of the oligopeptide chemoattractant receptor on guinea pig macrophages and macrophage membrane preparations were characterized using detailed binding studies and computer analysis. Viable macrophages bound the radiolabeled chemoattractant N-formyl-methionyl-leucyl-[3H]phenylalanine with single dissociation constant (KD) of 18.4 +/- 4.6 nM with 15,300 +/- 1,800 sites per cell. Binding data from membrane preparations indicated the presence of two classes of binding sites with KD of 1.5 +/- 0.4 nM and 25.5 +/- 11.0 nM. Approximately 23% of the receptors were in the high affinity state. In the presence of added guanine nucleotide di- or triphosphates, the high affinity receptors in the membrane preparations were converted to low affinity states with no change in the total receptor number. Nonhydrolyzable derivatives of GTP were most potent in converting the receptor from its high to low affinity state. These data suggest that the affinity state of the oligopeptide chemoattractant receptor in macrophages is regulated by guanine nucleotides and GTPase, implying that the transduction mechanisms of this receptor may be controlled by a guanine nucleotide regulatory unit.

Animals↗
PubMed1984

Chemoattractant receptors on phagocytic cells.

Chemoattractant receptors on leukocytes can trigger a number of cellular responses, including the cytoskeletal reorganization, changes in cell shape, directed motility, lysosomal enzyme secretion, and activation of the respiratory burst. The dose of chemoattractants required to induce motility-related functions is generally at least ten-fold smaller than the dose required to initiate secretory and respiratory burst activities. This finding and other pharmacological evidence clearly indicate that the two types of functions (i.e. motility and secretion) are regulated differently and can be divergently modified by drugs. The affinity of the oligopeptide chemoattractant receptor on polymorphonuclear leukocytes and macrophages is heterogeneous and dynamically regulated by guanine nucleotides and prior agonist exposure. High- and low-affinity forms of the oligopeptide receptor have been identified by direct binding studies. Our data suggest that low doses of agonists can initiate interconversion of low- and high-affinity states of that portion of chemoattractant receptors regulated by guanine nucleotides. On the other hand, high doses of agonists sufficient to induce chemotactic desensitization, lysosomal enzyme secretion, and the respiratory burst lead to the formation of a new population of high-affinity receptors. These binding sites are insensitive to the effects of guanine nucleotides and appear to be rapidly internalized. Transmethylation reactions mediated by S-adenosyl methionine are required for the activation of a phospholipase and release of arachidonate from leukocytes by chemotactic factors. We suggest that release of arachidonate from membrane phospholipid activates and translocates a cytosolic but loosely membrane-associated protein kinase C into the membrane and that this kinase participates in stimulus-response coupling of chemoattractant receptors.

Animals↗
PubMed1984

Rapid changes in light scattering from human polymorphonuclear leukocytes exposed to chemoattractants. Discrete responses correlated with chemotactic and secretory functions.

A platelet aggregometer was adapted for the simultaneous measurement of perpendicular light scattering in addition to light transmission. The addition of chemoattractants to polymorphonuclear leukocyte suspensions evoked a single wave of increased light transmission, whereas the perpendicular scattering measurement demonstrated a previously unrecognized biphasic response. The first perpendicular scattering response had no detectable latency and peaked at 10 +/- 1 s, then decayed rapidly. The second response peaked at 40 +/- 5 s, and decayed over several minutes. The dose-response curve of chemoattractants for inducing the rapid (10 +/- 1 s) perpendicular scattering peak corresponded to that which initiated chemotaxis. Initiation of the slow (40 +/- 5 s) peak required 10-fold higher amounts of chemoattractants, and the dose-response curve correlated with the induction of lysosomal enzyme secretion and superoxide anion production. Low doses of aliphatic alcohols, which have been shown to enhance chemotaxis but to inhibit secretion and superoxide anion production, abolished the slow perpendicular light-scattering response but left the fast response intact. Stimulants of secretion induced only slow and prolonged responses that were best observed in transmission measurements. In an attempt to resolve the origin of the light-scattering responses, the morphological changes of polymorphonuclear leukocytes were examined microscopically. Neither aggregation nor morphological whole cell polarization could be correlated with changes in light transmission or perpendicular scattering, which suggested that the source of scattering is of subcellular dimensions. The rapid perpendicular light-scattering response of polymorphonuclear leukocytes to chemoattractants appears to record an initial event in the stimulus-response coupling, and its measurement should provide a useful new tool for the study of leukocyte function. The biphasic nature of the light-scattering responses to chemoattractants, moreover, correlates with the dual regulation of the chemotactic and secretory responses of leukocytes.

Chemotaxis, Leukocyte↗
PubMed1984

Regulatory mechanisms of a chemoattractant receptor on leukocytes.

Chemoattractant receptors on leukocytes initiate a number of coordinated biochemical and biological processes in a strict dose-related manner. Chemotaxis-related functions occur at low doses of chemoattractants whereas the microbicidal or secretory functions (i.e., secretion of lysosomal enzymes and superoxide anion production) require 10- to 50-fold higher concentrations. The study of the oligopeptide chemoattractant receptor on human polymorphonuclear leukocytes (PMNs) has permitted better understanding of the regulation of leukocyte function. The receptor in leukocyte membranes exists in two affinity states, which are in part interconvertible. Convertibility between a portion of the high- and low-affinity states is regulated by guanine nucleotides, which suggests that a nucleotide regulatory unit allosterically modifies receptor affinity and participates in its transduction mechanisms. Approximately one-third of the high-affinity receptors in PMN membranes are not subject to guanine nucleotide regulation. This fraction can be increased by agonist preincubation and could represent an intermediate form of the receptor before signal transduction and/or internalization. Pharmacological manipulation of viable PMNs demonstrates that the affinity and functional activity of the chemoattractant receptor can be altered in different directions by aliphatic alcohols and polyene antibiotics. The alcohols raise the receptors' affinity and enhance chemotaxis, but markedly depress chemoattractant-induced secretory mechanisms. In contrast, polyene antibiotics lower the receptors' affinity and depress chemotaxis, but enhance specific granule secretion. Thus, the chemoattractant receptors' transduction signals for chemotaxis and secretion are discrete and can be modified independently by pharmacological techniques. A relationship exists between the chemoattractant receptors' affinity and its ability to transduce signals for either chemotaxis or secretion.

Amphotericin B↗
PubMed1984

A potential second messenger role for arachidonic acid: activation of Ca2+-dependent protein kinase.

A widely distributed Ca2+- and phospholipid-dependent protein kinase, protein kinase C, may play a major role in cellular regulation. We now report that arachidonate can directly activate protein kinase C from human neutrophils. Activation was Ca2+-dependent and was enhanced by diolein, but did not require phosphatidylserine. Arachidonate enhanced the apparent affinity of the kinase for Ca2+ in the presence of phosphatidylserine. Other unsaturated, but not saturated, fatty acids also activated protein kinase C. These results suggest a novel means of leukocyte activation and cellular regulation: arachidonate, which is released by ligand-receptor interactions in neutrophils and many other cell types, could function as a second messenger via activation and modulation of protein kinase C.

Arachidonic Acids↗
PubMed1984

Characterization of an oligopeptide chemoattractant receptor on human blood monocytes using a new radioligand.

The study of chemoattractant receptors on human monocytes had been limited by the lack of a radioligand suitable for use with the small numbers of cells routinely available from human donors. A new synthetic oligopeptide radioligand f[35S]met-leu-phe, with a higher specific radioactivity than was available with the tritiated compound, was used to characterize a chemoattractant receptor on freshly isolated human blood monocytes. These cells bind f[35S]met-leu-phe with a dissociation constant (KD) of 30.2 +/- 5.6 nM and contain 84,000 +/- 11,300 receptors per cell. f[35S]met-leu-phe does not bind specifically to blood lymphocytes. The specificity of the oligopeptide receptor on monocytes is indistinguishable from the oligopeptide chemoattractant receptor on human polymorphonuclear leukocytes. Using f[35S]met-leu-phe, it will now be feasible to study the chemotactic peptide receptor on small numbers of partially purified peripheral blood monocytes from patients with defects of immune function.

Animals↗
PubMed1984

Light scattering by polymorphonuclear leukocytes stimulated to aggregate under various pharmacologic conditions.

Enhancement of light transmission has been widely accepted as an empirical measure of cell aggregation in suspension. Several years ago, this measurement was introduced to the study of polymorphonuclear leukocyte (PMN) aggregation by adapting a hypothesis originally developed for platelets. Accordingly, an increase in light transmission is attributed to cell aggregation and a decrease in transmission below baseline level is indicative of increased cell symmetry. We tested this hypothesis for human PMNs by comparing the whole cell shape or the cells' aggregation state with the light transmission under particular experimental conditions. The PMN light response to the chemoattractant, f-Met-Leu-Phe, in the presence of low doses of aliphatic alcohols was associated with transient enhanced transmission, followed by a rapid decrease below baseline. In contrast to the platelet hypothesis, the below-baseline effect coincided with a decrease in PMN symmetry from spheres to wedge-shaped (polarized) cells. PMNs fixed mildly with various doses of formaldehyde (0.1% to 0.3%) were completely aggregated by the addition of 50 micrograms/mL phytohemagglutinin (PHA). Despite the complete aggregation of the PMNs, there was a dose-dependent inhibition of the above-baseline level transmission response by the fixative, demonstrating a clear dichotomy between aggregation and increased light transmission. However, PMN aggregation could be monitored by observing the pattern of enhanced light transmission coupled with decreased perpendicular light scattering immediately after the stirring of the cell suspensions was stopped. PMNs aggregated by PHA cleared from suspension very rapidly (t1/2 less than or equal to one minute), whether or not they were formalin-fixed. In contrast, unaggregated cells revealed constant transmission and perpendicular scattering intensities for as long as five minutes after the stirring was stopped. The clearance patterns of f-Met-Leu-Phe-stimulated PMNs initiated even at the time of maximally increased light transmission were indistinguishable from those of the unstimulated cells, indicating the absence of aggregation. The lack of correlation between light output and changes in cell shape or degree of aggregation of PMNs causes us to reject the hypothesis that attributes enhanced light transmission to PMN aggregation. We suggest that modulation of light transmission by PMNs stimulated with chemoattractants is due to changes in light output from subcellular objects.

1-Butanol↗
PubMed1983

Pharmacologic manipulation of leukocyte chemotaxis. Present knowledge and future trends.

The chemotactic responses of leukocytes are initiated by the binding of chemoattractants to specific cell-surface receptors. At larger doses, chemoattractants stimulate other biologic activities in leukocytes, including the production of superoxide anions and the secretion of lysosomal enzymes. The tissue-destructive properties of inflammatory cells relate largely to these latter two biologic responses. It has recently been shown that the oligopeptide chemotactic factor receptor in human polymorphonuclear leukocyte membranes exists in high- and low-affinity states that are interconvertible and regulated by guanine nucleotides. In whole polymorphonuclear leukocytes, only one affinity of the receptor can be seen due to rapidly ongoing cellular processes. This affinity can be modified by agents that alter the physical state of the membrane and can be enhanced by aliphatic alcohols, agents that decrease membrane microviscosity. Under these conditions, the chemotactic responsiveness of polymorphonuclear leukocytes is enhanced, but lysosomal enzyme secretion and superoxide anion production are markedly depressed. Polyene antibiotics, which bind membrane cholesterol, decrease the affinity of the receptor. These agents also depress chemotaxis but enhance lysosomal enzyme secretion. These findings indicate that the transduction mechanisms for certain biologic responses initiated by chemoattractant receptors are heterogeneous. The particular transduction pathway initiated by chemotactic factors is reflected by the affinity state of the receptor. The higher affinity initiates chemotaxis whereas the lower affinity initiates lysosomal enzyme secretion and superoxide anion production. These findings suggest that pharmacologic agents may well be developed, which can selectively affect the specific functions of polymorphonuclear leukocytes in man. Anti-inflammatory agents that can decrease leukocyte lysosomal enzyme secretion and superoxide anion production, but not chemotaxis, may well be useful in the treatment of certain rheumatic diseases.

Amphotericin B↗
PubMed1983

Murine malignant cells synthesize a 19,000-dalton protein that is physicochemically and antigenically related to the immunosuppressive retroviral protein, P15E.

Murine tumors contain low molecular weight factors that inhibit macrophage accumulation at inflammatory foci. Certain oncogenic murine leukemia viruses contain similar inhibitory activity and the active component of the retroviruses was shown to be the envelope protein P15E. A number of murine malignant and nonmalignant cell lines, as well as primary tumors, have now been examined to determine whether production of retroviral P15E or a related protein is characteristic of neoplastic cells. Tumor lines examined included the Hep 129 hepatocarcinoma, BP8 fibrosarcoma, RL1 lymphoma, and three variants of the B16 melanoma. Tumor lines were virus negative by electron microscopy. Nonmalignant cells examined included ST0, 3T3/BALB, and 3T3/L1 fibroblasts and unstimulated, as well as mitogen-stimulated murine splenocytes. Cells were pulse-labeled with [35S]methionine, proteins immunoprecipitated with two monoclonal antibodies to P15E and analyzed by SDS-PAGE and gel fluorography. All tumor lines synthesized a approximately 19,000-dalton protein that co-migrated with retroviral P15E on SDS-PAGE. None of the nonmalignant cells synthesized this protein. Two-dimensional gel electrophoresis of the proteins precipitated from two B16 melanoma lines by monoclonal anti-P15E showed them to be physicochemically similar to P15E from Rauscher leukemia virus. A competition ELISA assay for P15E was developed and confirmed the results obtained by metabolic labeling and demonstrated P15E-related antigens in the tumor cell lines and also in the ascites fluid of mice injected with Hep 129 cells. More importantly, P15E antigens were expressed in both a spontaneous mammary adenocarcinoma and in a primary methylcholanthrene-induced fibrosarcoma. Nonmalignant tissues from animals bearing these tumors contained no detectable P15E antigen. Extracts from the primary fibrosarcomas, when injected into the thighs of mice, inhibited the intraperitoneal accumulation of inflammatory macrophages. The inhibitory activity was specifically removed by absorption with monoclonal antibody to P15E. These results suggest that synthesis of the immunosuppressive retroviral protein P15E, or a very similar protein, routinely occurs during the growth of murine neoplastic cells. This P15E-related protein is present in spontaneous murine primary tumors as well as in all murine tumor cell lines tested. The expression of such proteins by transformed cells in vivo could confer a selective advantage for their sustained growth since they would be more likely to escape immune surveillance.

Animals↗
PubMed1983

Chemoattractant receptor affinity reflects its ability to transduce different biological responses.

The oligopeptide chemotactic factor receptor in human PMN membranes exists in two affinity states which are in part interconvertible and regulated by guanine nucleotides. In whole cells, only one affinity of the receptor can be seen, presumably due to the high intracellular levels of guanine nucleotides as well as rapidly ongoing cellular processes which allow the detection of only a single affinity state. There is strong evidence to suggest that the affinity of the chemoattractant receptor in whole PMNs can be modified by agents which alter the physical state of the PMN membrane. The average affinity of the oligopeptide chemotactic factor receptor can be enhanced by aliphatic alcohols which decrease membrane microviscosity. Under these conditions, chemotactic responsiveness of PMNs is enhanced but 0(2-) production and secretion initiated by chemoattractants is markedly depressed. When the affinity of the receptor is lowered as in the case of amphotericin B, chemotaxis is depressed but lysozyme secretion is enhanced. These data indicate that the transduction mechanisms for certain biological responses initiated by the chemoattractant receptor are heterogeneous. It can be hypothesized that the particular transduction pathway initiated by chemoattractant receptor occupancy is reflected by the affinity state of the receptor. The higher affinity state initiates chemotactic signals whereas the lower affinity state initiates 0(2-) production and secretion. By altering the affinity of the receptor using pharmacological means one may be able to modify the biological activity of human PMNs.

Alcohols↗
PubMed1983

Polymorphonuclear leukocyte function in psoriasis: chemotaxis, chemokinesis, beta-adrenergic receptors, and proteolytic enzymes of polymorphonuclear leukocytes in the peripheral blood from psoriatic patients.

Psoriatic patients, particularly those with psoriatic arthritis, have neutrophilic and eosinophilic leukocytosis. Isolated polymorphonuclear leukocytes (PMNLs) from psoriatic patients have normal concentrations of proteolytic enzymes and they have beta-adrenergic receptors of normal density and affinity. PMNLs from psoriatic patients responded normally to the synthetic chemotactic peptide, f-Met-Leu-Phe (formyl-methionine-leucine-phenylalanine). The chemotactic activities of sera from psoriatic patients were similar to those of normal sera. Sera from psoriatic patients enhanced chemokinesis of PMNLs more than normal control sera at a final concentration of 1%; no difference in chemokinetic response between psoriatic and normal sera was found at serum concentrations greater than 2.5%. This study suggests that the peripheral PMNLs from psoriatic patients are normal, but the sera of psoriatic patients has more chemokinetic activity for PMNLs than does normal serum.

Chemotaxis, Leukocyte↗
PubMed1983

Effect of membrane fluidizers on the number and affinity of chemotactic factor receptors on human polymorphonuclear leukocytes.

Chemotaxis by leukocytes appears to be initiated by the binding of chemo-attractants to specific cell surface receptors. In other biological systems, the affinity and functional activity of membrane receptors are regulated by the local microviscosity. The present studies were undertaken to determine if the number and/or affinity of chemotactic factor receptors expressed on human polymorphonuclear leukocytes were similarly affected. Aliphatic alcohols and cis-vaccenic acid, agents known to decrease membrane microviscosity, were studied for their effects on the binding of the radiolabeled chemoattractant f-Met-Leu-[3H]Phe to human polymorphonuclear leukocytes. Butanol and propanol increased the number of f-Met-Leu-[3H]Phe binding sites approximately 1.5 fold. More dramatically, these same agents enhanced the affinity of the receptor by ten-fold, without affecting the specificity of the receptor. Similarly, cis-vaccenic acid enhanced both the number and affinity of this chemotactic factor receptor on human polymorphonuclear leukocytes contain cryptic receptors for the N-formylated peptide chemotactic factors, but more importantly that the affinity of these receptors can exist in more than one state and can be modulated by membrane microviscosity. Alterations of membrane fluidity in leukocytes during chemotaxis may be an important mechanism for regulating their sensitivity to chemoattractants.

Alcohols↗
PubMed1983

Induction of selective biological responses to chemoattractants in a human monocyte-like cell line.

The availability of monocyte cell lines that can be induced to differentiate in a predictable fashion can provide important tools for the study of the biochemical mechanisms of specific cellular responses. The U937 human monocyte cell line was previously shown to differentiate into chemotactically responsive cells when incubated with supernatants of lectin-stimulated lymphocytes (conditioned medium). Considering the heterogeneous nature of stimulated lymphocyte supernatants, attempts were made to identify well-defined agents that could reproducibly induce U937 cell differentiation. Both dimethyl sulfoxide and dibutyryl cAMP induced expression of receptors for the N-formylated oligopeptide chemoattractants in U937 cells. Unstimulated U937 cells contained no detectable receptors. After cells were exposed to 1 mM dibutyryl cAMP, 1.3% dimethyl sulfoxide, or 5% conditioned medium for 72 h, the average number of oligopeptide chemoattractant receptors per U937 cell was 33,000, 4,000, and 3,400, respectively. Specific binding proteins for the chemoattractants were identified by covalent affinity labeling on the differentiated U937 cells as well as on normal human monocytes. Cells exposed to conditioned medium responded chemotactically, secreted lysosomal enzymes, and formed superoxide anion when incubated with the chemoattractant. Treatment of U937 cells with dibutyryl cAMP resulted in the most reproducible and rapid increase in the number of chemoattractant receptors as well as in chemotactic responsiveness. The receptors on dibutyryl cAMP-treated cells and on dimethyl sulfoxide-treated cells initiated chemotaxis and lysosomal enzyme secretion in response to chemoattractants, but not the formation of superoxide anion. These findings demonstrate that development of the chemotactic and respiratory burst functions during the differentiation of a monocyte-like cell line can occur independently.

Bucladesine↗