Biomedical subjects

K M Skubitz

Publications and source records attributed to K M Skubitz.

At least 73 records · Page 4Linked to original sources

PubMed1989

Impermeant stilbene disulfonic acids block chemotactic peptide receptor function on human granulocytes.

Anion transport is important in a variety of cell functions. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS) are two impermeant agents that have been reported to specifically block the anion channel in erythrocytes. These agents block several responses of human neutrophils to stimulation by immune complexes, the synthetic chemotaxin N-formyl-met-leu-phe (FMLP), and a calcium ionophore. They also alter the function of C3b receptors on the neutrophil surface. We studied the effects of DIDS and SITS on the aggregation of human neutrophils, a process that has been implicated in a number of diverse clinical syndromes. Both DIDS and SITS inhibited granulocyte aggregation induced by FMLP, zymosan-activated plasma, 12-O-tetra-decanoylphorbolmyristate acetate (TPA), and the calcium ionophore A23187. To further study the mechanism of inhibition the effects of DIDS and SITS on FMLP-receptor function were tested. Similar concentrations of the anion channel blockers also inhibited binding of radiolabeled FMLP to its specific receptor on the neutrophil surface. Inhibition of binding was due to a decrease in both the number and affinity of the surface receptors available for FMLP; DIDS did not inactivate FMLP. The effects of stilbene disulfonic acid on cell function may be due to effects of these agents on other cell-surface structures in addition to the anion channel.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1988

CD15 monoclonal antibodies react with a phosphotyrosine-containing protein on the surface of human neutrophils.

mAb are useful as probes in the study of the roles of cell-surface components in neutrophil function. Many mAb that bind to human neutrophils react with the oligosaccharide lacto-N-fucopentaose III (CD15 antibodies). These antibodies, as well as several other widely used mAb reactive with human neutrophils, were employed to detect phosphoproteins present on these cells. Immunoprecipitation and subsequent gel electrophoresis of proteins from neutrophils labeled with [gamma-32P]ATP revealed a 170 to 190-kDa phosphoprotein specifically reactive with CD15 antibodies. No phosphoproteins were immunoprecipitated by CD11 or CD18 mAb. Phosphoamino acid analysis of the 170- to 190-kDa protein showed that it contained predominantly phosphotyrosine and a low level of phosphoserine. Recently, it was shown that this phosphoprotein is one of the major substrates of ecto-protein kinase activity on human neutrophils. The roles for the 170- to 190-kDa phosphoprotein and the ecto-protein kinase in neutrophil function remain to be determined.

Antibodies, Monoclonal↗

PubMed1988

Evidence for ecto-protein kinase activity on the surface of human neutrophils.

Recent studies have suggested a possible role for extracellular ATP in neutrophil function. This report provides evidence for the existence of an ecto-protein kinase activity on the surface of human neutrophils capable of phosphorylating intrinsic cell membrane proteins as well as exogenous proteins. Addition of extracellular [gamma-32P]ATP to neutrophils resulted in rapid incorporation of 32P into cellular proteins that were sensitive to trypsin. The ability of adherent cells to phosphorylate the exogenous substrate casein, while no protein kinase activity was released into the supernate, provided further evidence for a cell surface associated protein kinase activity.

Adenosine Triphosphate↗

PubMed1988

Preparation and characterization of a monoclonal antibody that inhibits human neutrophil elastase activity.

Neutrophil proteases are believed to play a role in the pathogenesis of a variety of human diseases. While many studies of proteases in models of disease have focused on elastase, neutrophils contain several proteases some of which share a high degree of homology. This report describes the production and characterization of an IgG1 murine monoclonal antibody (AHN-10) that reacts with human neutrophil elastase but not with the other major neutrophil neutral proteases: cathepsin G, proteinase 3, collagenase, or the newly purified neutral protease, esterase N. AHN-10 inhibited the elastinolytic activity of purified human neutrophil elastase and could detect elastase in alcohol-fixed cytospin preparations. The epitope recognized by AHN-10 was resistant to treatment with NaIO4, suggesting that the epitope is not a carbohydrate. AHN-10 should be useful for the immunolocalization of neutrophil elastase in tissue specimens and as a stable source of characterized antibody for quantitative identification of neutrophil elastase.

Animals↗

PubMed1988

Nephrotoxicity of continuous intravenous infusion of recombinant interleukin-2.

Adoptive immunotherapy with recombinant interleukin-2 has been complicated by significant nephrotoxicity of uncertain etiology. Creatinine clearance, effective renal plasma flow, plasma renin activity, aldosterone levels, and urinary prostaglandin excretion were evaluated in a 62-year-old man receiving continuous infusion recombinant interleukin-2. There was a marked decrease in the creatinine clearance and renal plasma flow, accompanied by an elevation in plasma renin activity and aldosterone level. Prostaglandin excretion also decreased, implying a direct effect on renal prostaglandin synthesis. The decrease in renal prostaglandin synthesis at a time of increased plasma renin activity may explain the reduction in renal function seen with recombinant interleukin-2 therapy.

Aldosterone↗

PubMed1988

Proteinase 3. A distinct human polymorphonuclear leukocyte proteinase that produces emphysema in hamsters.

Studies were designed to explore the possibility that human polymorphonuclear leukocyte granule constituents in addition to elastase (HLE) had the potential to cause emphysema. A two-step purification of three serine proteinases was developed. Granule extract proteins were initially separated by dye-ligand affinity chromatography. Fractions eluted were divided into four pools. Hamsters were given a single intratracheal instillation of saline +/- 0.1 mg protein of each pool. While pool 2 contained HLE and cathepsin G, the most dramatic bullous emphysema developed in animals treated with pool 4. The esterase from pool 4, designated proteinase 3 (PR-3) was purified, characterized in vitro, and tested for its ability to cause emphysema. PR-3 is a neutral serine proteinase with isoenzyme forms. Its ability to degrade elastin at pH 6.5 is slightly greater than that of HLE, but it is less active than HLE at pH 7.4 or 8.9. PR-3 has weak activity against azocasein. Its ability to degrade hemoglobin is intermediate to that of HLE and cathepsin G at pH 7.4. PR-3 has no activity against chromogenic substrates specific for HLE or cathepsin G. Its pI is substantially less than HLE or cathepsin G. It is also immunologically distinct from HLE. It induces emphysema in hamsters commensurate with that of HLE. We conclude that PR-3 may be important in the pathogenesis of human emphysema.

Animals↗

PubMed1988

Endogenous and exogenous adenosine inhibit granulocyte aggregation without altering the associated rise in intracellular calcium concentration.

The effects of adenosine, adenosine deaminase (ADA), and an irreversible ADA inhibitor 2'-deoxycoformycin (DCF) on granulocyte aggregation in response to four different stimuli: the synthetic chemotaxin N-formyl-met-leu-phe (FMLP), zymosan-activated plasma (ZAP), the calcium ionophore A23187, and phorbol myristate acetate (PMA) were studied. Adenosine inhibited granulocyte aggregation in response to 10(-7) mol/L FMLP in a dose-dependent fashion; inhibition in the presence of 1 mumol/L adenosine was 25% +/- 3% (SD) and was 50% (the maximal inhibition observed) with 1 mmol/L adenosine. Quantitatively similar results were obtained when ZAP or A23187 was used as the aggregant but the response to PMA was not affected. ADA not only reversed the inhibition due to adenosine but actually augmented the aggregation to FMLP by 118% +/- 9%. Similar results were obtained with ZAP and A23187 but not with PMA. These effects of ADA depended on its enzymatic activity as they could be blocked by preincubation with DCF. Fluorescent measurement of intracellular calcium in fura-2 loaded granulocyte suspensions established that neither adenosine nor ADA affected subsequent FMLP-stimulated calcium responses. Adenosine, therefore, may inhibit granulocyte responsiveness by blocking signal transduction at a point after calcium entry/mobilization but before activation of protein kinase C. Furthermore, the augmentation of responses seen with ADA suggests that endogenous adenosine may be a physiologic autocrine regulator of granulocyte function.

Adenosine↗

PubMed1988

Identification of the major lectin-binding surface proteins of human neutrophils and alveolar macrophages.

Concanavalin A (Con A) and wheat germ agglutinin (WGA) are frequently used as stimuli of neutrophils and macrophages. While the effects of these lectins on cell function are presumably mediated by interaction with cell-surface molecules, the target structures on the cell surface involved are not well defined. We have used the techniques of lactoperoxidase catalyzed cell-surface iodination, lectin affinity chromatography, monoclonal antibody immunoprecipitation, and NaDodSO4-polyacrylamide gel electrophoresis to study the surface proteins of human neutrophils and alveolar macrophages that react with six lectins including Con A and WGA. We found that several major surface-labeled proteins of neutrophils bound Con A. Four of these proteins were identified by immunoprecipitation as members of the LFA-1/HMac-1/gp150,95 adhesion glycoprotein family. Con A also bound CR1 and a 135-kd surface-labeled protein recognized by CD15 monoclonal antibodies. WGA also bound many of these proteins, but had a much lower avidity for CR1. All three of the major surface-labeled proteins of human alveolar macrophages bound to Con A, including the 183-kd mannose receptor and the 30-kd smoking-associated protein. WGA also bound the 183-kd macrophage protein, but not the 30-kd protein. These results should aid the understanding of studies using these lectins as stimuli.

Antibodies, Monoclonal↗

PubMed1987

Monoclonal antibodies that recognize lacto-N-fucopentaose III (CD15) react with the adhesion-promoting glycoprotein family (LFA-1/HMac-1/gp 150,95) and CR1 on human neutrophils.

A variety of monoclonal antibodies has been used to study the roles of surface proteins in neutrophil function. Many monoclonal antibodies that bind to human neutrophils react with the oligosaccharide lacto-N-fucopentaose III. Sequential immunoprecipitation of radiolabeled proteins from extracts of neutrophils labeled at the cell surface with 125I, and partial proteolysis peptide mapping studies were used to compare the proteins recognized by several widely used monoclonal antibodies that react with human neutrophils. The monoclonal antibodies that react with lacto-N-fucopentaose III (CD15) immunoprecipitated five distinct neutrophil surface proteins. The data indicate that CD15 monoclonal antibodies react with a subset of the LFA-1/HMac-1/gp 150,95 glycoprotein family as well as with CR1 on human neutrophils. The CD15 antibodies studied differed in their avidities for these proteins. The molecules immunoprecipitated by the CD15 antibodies tested were more resistant to proteolysis than the homologous proteins immunoprecipitated by the other monoclonal antibodies studied that react directly with the alpha M (CD11) or beta (CD18) chains of the LFA-1/HMac-1/gp 150,95 glycoprotein family. Some of the differences in antibody reactivity and protease sensitivity of the membrane proteins recognized by these antibodies may be due to differences in glycosylation. The data suggest that the antibodies studied can detect differences in post-translational modification among copies of certain surface proteins.

Antibodies, Monoclonal↗

PubMed1987

Changes in the cell surface protein composition of human alveolar macrophages induced by smoking.

The cell surface proteins of human alveolar macrophages obtained from nonsmokers have been compared to those of alveolar macrophages obtained from smokers. Proteins of nonsmokers' alveolar macrophages surface labeled with 125I differed from those of smokers' alveolar macrophages, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Three major radiolabeled proteins with molecular weights of 183,000, 80,000, and 30,000 were identified in fresh smokers' cells. The major radiolabeled protein of nonsmokers' macrophages had an apparent molecular weight of approximately 183,000. Affinity chromatography suggested the Mr 183,000 protein is a mannose receptor. In contrast, the molecular weight of the major radiolabeled protein of smokers' alveolar macrophages was approximately 30,000; the Mr 183,000 protein was less prominent. When nonsmokers' alveolar macrophages were cultured in vitro before 125I labeling, the cell surface protein pattern changed to resemble that of smokers' alveolar macrophages; the Mr 183,000 protein could no longer be detected on the cell surface, whereas a Mr 80,000 protein was increased in quantity and a new Mr 30,000 protein was detected. Nonadherent macrophages showed similar changes in their surface-labeled proteins but also contained a new prominently labeled Mr 70,000 protein. Limited proteolysis peptide mapping with five different enzymes did not reveal any evidence of homology among the Mr 183,000, 80,000, 70,000, and 30,000 proteins. The differences in cell surface protein composition between alveolar macrophages of smokers and nonsmokers may reflect their functional capabilities or their state of "activation" and may be mechanistically important in the development of various pulmonary diseases seen in smokers including cancer. These results also demonstrate that major changes in the surface proteins of the human alveolar macrophage plasma membrane can occur rapidly following manipulation.

Affinity Labels↗

PubMed1987

Identification and purification of the human myeloid differentiation antigen recognized by monoclonal antibody AHN-7.

This report describes the characterization and expression of a human myeloid differentiation antigen defined by use of an IgG1 monoclonal antibody (AHN-7). This antibody binds to many granulocytic precursors in normal marrow, to most but not all granulocyte-macrophage progenitors (CFU-GM), and to approximately half of nonlymphoid leukemia specimens. The protein antigens recognized by AHN-7 were purified from 35S-labelled HL-60 cells by antibody affinity column chromatography. The molecule reacting with AHN-7 was markedly heterogeneous, appearing as several forms ranging in pl from 4.5 to 6.4 with apparent molecular weights from 43,000 to 68,000. The molecules were not disulfide-linked. Proteins bearing the antigen were minor components of the plasma membrane. The antigen was expressed by normal human peripheral blood neutrophils, monocytes, eosinophils, and basophils, and weakly on a small percentage of lymphocytes; it was not detected in red blood cells, platelets, or the majority of lymphocytes. The antibody also bound to a variety of human myeloid leukemia cell lines but not to any lymphoid leukemia cell line tested. AHN-7 had no effect on several in vitro neutrophil functions tested.

Antibodies, Monoclonal↗

PubMed1987

Changes in neutrophil surface protein composition accompany phagocytosis.

Phagocytosis is a critical host defense mechanism of neutrophils. In this study, membrane protein changes occurring during phagocytosis were studied in human neutrophils using surface radiolabeling before or after phagocytosis of various target particles. Cells were labeled at the cell surface using lactoperoxidase-catalyzed iodination or neuraminidase-galactose oxidase-NaB3H4, galactose oxidase-NaB3H4, or periodate-NaB3H4 techniques. Such studies are complicated by the fact that these techniques identify many surface proteins on the phagocyte, and labeling after phagocytosis occurs often results in radiolabeling proteins of the target particle, thus making changes in cell-surface proteins more difficult to detect. Immunoprecipitation with monoclonal antibody AHN-1, which reacts with a carbohydrate present on several human neutrophil surface proteins and inhibits phagocytosis, eliminated interference caused by radiolabeled proteins of the target particle and simplified analysis by restricting the study to a limited number of proteins. AHN-1 immunoprecipitated less radiolabeled protein from neutrophils labeled after phagocytosis of particles opsonized with IgG or complement than from cells labeled before phagocytosis. Isolation of phagocytic vesicles containing opsonized emulsified paraffin oil demonstrated that three proteins of mol wt 105,000, 140,000, and 170,000 recognized by AHN-1 were internalized in the phagocytic vesicle during phagocytosis.

Antibodies, Monoclonal↗

PubMed1986

Effects of ibuprofen on chemotactic peptide-receptor binding and granulocyte response.

Inhibition of complement-mediated granulocyte aggregation has been proposed recently as a mechanism of action of high-dose corticosteroids and ibuprofen in shock states. Such inhibition by corticosteroids may be effected through alteration of receptor function, and we have therefore examined the effect of ibuprofen on the extent and kinetics of binding of the synthetic chemotactic peptide formylmethionine-leucine-phenylalanine (FMLP) to its specific receptor on the granulocyte surface. Dose-dependent inhibition of binding was observed at ibuprofen concentrations paralleling plasma levels achieved with 30 mg/kg intravenous bolus therapy, and also at concentrations achieved with oral therapy. Ibuprofen did not affect the receptor number, but did decrease the association rate constant for the FMLP-receptor interaction (30% of normal for 0.125 mg/ml ibuprofen), leading to a decrease in receptor affinity for ligand. Dissociation kinetics, as determined by cold chase experiments, were unaltered by ibuprofen. We conclude that ibuprofen, like corticosteroids, can slow the rate of association of FMLP with its receptor on the granulocyte surface while allowing dissociation to proceed; altered kinetics of receptor-FMLP interaction may explain the inhibition of granulocyte aggregation. Blockade of granulocyte surface receptors for inflammatory stimuli may be important in the clinical effects of very high-dose corticosteroids and ibuprofen such as are administered in shock; such effects are seen at blood levels of ibuprofen that occur with oral therapy. Similar observations may hold for other physiologic stimuli.

Cell Aggregation↗

PubMed1986

Corticosteroids reversibly inhibit chemotactic peptide-receptor binding and granulocyte response, yet allow desensitization and receptor down-regulation.

Inhibition of complement-mediated granulocyte aggregation has recently been proposed as a mechanism of action of high-dose corticosteroids in shock states. Such inhibition may be effected through alteration of receptor function. Methylprednisolone inhibits binding of the synthetic chemotaxin f-methionine-leucine-phenylalanine (FMLP) to its surface receptor on granulocytes in a dose-dependent manner by slowing the association rate of the FMLP-receptor interaction without altering receptor number. Because the half-life of high-dose methylprednisolone in vivo is short, we examined the reversibility of its effects on granulocyte aggregation and receptor function; both effects were readily reversed by washing. Furthermore, methylprednisolone, at concentrations that profoundly inhibited the granulocyte aggregation response to FMLP, allowed the occurrence of FMLP-receptor down-regulation and granulocyte desensitization to further stimulation by FMLP. We conclude that methylprednisolone at concentrations that inhibit granulocyte aggregation can slow the rate of the FMLP-receptor interaction while simultaneously allowing receptor down-regulation and granulocyte desensitization to proceed. Transient blockade of granulocyte function with concomitant desensitization and receptor down-regulation may be important in the clinical effects of very high-dose corticosteroids such as are administered in shock and could partially explain how drugs with such short half-lives administered intermittently could exert a beneficial effect in shock states. Similar observations may hold for other physiologic stimuli.

Cell Aggregation↗

PubMed1985

Characterization of cell surface glycoproteins recognized by the granulocyte-specific monoclonal antibody, AHN-1.

Major surface-iodinated proteins of Mr 105,000 and 145,000 of normal human neutrophils are immunoprecipitated by a number of monoclonal antibodies (AHN-1 to AHN-6), which react specifically with granulocytes among peripheral blood cells and selectively inhibit phagocytosis. These proteins, and an Mr 60,000 component, were purified by monoclonal antibody affinity chromatography, molecular sieve chromatography, and preparative polyacrylamide gel electrophoresis. Each of the three purified proteins was immunoprecipitated by all six antibodies. Nevertheless, tryptic peptide maps of the three proteins indicated that each was a distinct component. AHN-1 to AHN-6 also bound to glycolipid fractions of human neutrophils, and the binding of each antibody to human neutrophils was blocked by the carbohydrate sequences, lacto-N-fucopentaose III. The data indicate that a predominant antigenic determinant of human neutrophils is lacto-N-fucopentaose III, or related carbohydrates, present on three distinct proteins as well as glycolipids. At least one of these molecules appears to be involved in the process of phagocytosis.

Antibodies, Monoclonal↗

PubMed1985

Monoclonal antibody AHN-1 inhibits phagocytosis by human neutrophils.

The granulocyte-specific monoclonal antibody, AHN-1, immunoprecipitates two major surface-iodinated proteins of 105,000 and 145,000 to 150,000 daltons from normal human neutrophils. In this study, the effect of AHN-1 on a number of neutrophil functions was evaluated in vitro. Both complement- and antibody-mediated phagocytosis were inhibited when human neutrophils were pretreated with AHN-1 and opsonized bacteria were used as targets. The inhibition of phagocytosis was specific, in that lysosomal enzyme release and chemotaxis were not altered by treatment with AHN-1. AHN-1 did inhibit superoxide production by neutrophils in response to particulate stimuli, but not in response to the soluble stimulus, 12-O-tetradecanoylphorbol-13-acetate. The data indicate that one or both of these surface proteins may be important in the process of phagocytosis. AHN-1 should be useful in isolating and further characterizing the nature of these molecules.

Animals↗

PubMed1984

Antigenic analysis of hematopoiesis: II. Expression of human neutrophil antigens on normal and leukemic marrow cells.

The binding of five antineutrophil monoclonal antibodies AHN-1, -2, -3, -7, and -8, to normal and leukemic bone marrow cells was studied. AHN-7 bound to many granulocytic precursors, particularly myelocytes, and both lymphoid and blast cells in normal marrow, and to most but not all granulocyte-macrophage progenitors (CFC-GM). AHN-8 bound only to late (band and segmented) neutrophilic cells and not to CFC-GM. AHN-1, -2, -3 bound to morphologically identifiable neutrophil precursors, but not to (day-14) CFC-GM. Approximately half of nonlymphoid leukemia specimens were positive with AHN-1 or AHN-7; by contrast, lymphoid leukemia specimens were rarely positive. AHN-8 was rarely found on leukemic cells. These antineutrophil antibodies appear to detect distinct granulopoietic subsets and may be useful in the analysis of hematologic differentiation and in the subclassification of leukemias.

Animals↗

PubMed1983

Chronic myelogenous leukemia. Development of blast crisis with both lymphoid and myeloid features.

A 50-year-old man had chronic myelogenous leukemia and entered a blast crisis that was both morphologically and histochemically lymphoid. The blasts contained terminal deoxyribonucleotidyl transferase and expressed lymphoblastic leukemia-associated antigen. He rapidly entered remission with vincristine sulfate and prednisone therapy. Nevertheless, his blasts displayed a marker generally considered unique to myeloid cells: they selectively bound the granulocyte chemotaxin N-formyl-Met-Leu-Phe. In addition, some cells contained granules resembling those of basophils or mast cells. Such mixed myeloid-lymphoid features in chronic myelogenous leukemia blast cells may reflect malignant transformation of a stem cell capable of both myeloid and lymphoid differentiation, or they may reflect the dedifferentiation as a feature of malignant change.

Antigens, Neoplasm↗