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K M Skubitz

Publications and source records attributed to K M Skubitz.

At least 19 recordsLinked to original sources
PubMed2001

Homophilic adhesion of human CEACAM1 involves N-terminal domain interactions: structural analysis of the binding site.

CEACAM1 on leukocytic, endothelial, and epithelial cells functions in homophilic adhesion, tumor suppression, regulating cell adhesion and proliferation, and in heterophilic adhesion as a receptor for E-selectin and Neisseria meningiditis, Neisseria gonorrhoeae, Haemophilus influenzae, and murine coronaviruses. The 8 transmembrane isoforms of human CEACAM1 possess an extracellular N-terminal IgV domain, followed by variable numbers of IgC2 domains. To establish which key amino acids contribute specifically to CEACAM1 homophilic adhesion, exposed amino acids in the N-terminal domain of a soluble form of CEACAM1 were subjected to mutagenesis. Analyses of mutant proteins with conformationally dependent antibodies indicated that most mutations did not substantially affect the structural integrity of CEACAM1. Nevertheless, decreased adhesion was observed for the single mutants V39A or D40A (single-letter amino acid codes) in the CC' loop and for the triple mutants located in the GFCC'C" face of the N-terminal domain. Interestingly, whereas single mutations in R64 or D82 that are predicted to form a salt bridge between the base of the D and F beta strands close to the critical V39 and D40 residues also abolish adhesion, an amino acid swap (R64D and D82R), which maintains the salt bridge was without significant effect. These studies indicate that the CC' loop plays a crucial role in the homophilic adhesion of CEACAM1. They further predict that specific hydrophobic amino acid residues on the nonglycosylated GFCC'C" face of CEACAM1 N-terminal domain are not only involved in heterophilic interactions with Opa proteins and H influenzae, but are also critical for protein-protein interactions between 2 CEACAM1 molecules on opposing cells.

Amino Acid Sequence↗
PubMed2001

The functional interactions between CD98, beta1-integrins, and CD147 in the induction of U937 homotypic aggregation.

CD98 is expressed on both hematopoietic and nonhematopoietic cells and has been implicated in a variety of different aspects of cell physiology and immunobiology. In this study, the functional interactions between CD98 and other adhesion molecules on the surface of the promonocyte line U937 are examined by means of a quantitative assay of cell aggregation. Several of the CD98 antibodies induced homotypic aggregation of these cells without affecting cellular viability or growth. Aggregation induced by CD98 antibodies could be distinguished from that induced by beta1-integrin (CD29) ligation by lack of sensitivity to EDTA and by increased sensitivity to deoxyglucose. Aggregation induced via CD98 and CD29 could also be distinguished by the pattern of protein tyrosine phosphorylation induced. Some CD29 antibodies partially inhibited CD98-induced aggregation, and these antibodies were neither agonistic for aggregation nor inhibitors of beta1-integrin binding to substrates. Conversely, some CD98 antibodies were potent inhibitors of CD29-induced aggregation. Antibodies to beta2 integrins also partially inhibited CD98-induced aggregation. Unexpectedly, 2 antibodies to CD147, an immunoglobulin superfamily member whose function has remained unclear, were also potent inhibitors of both the aggregation and the protein tyrosine phosphorylation induced via CD98 ligation. The results of this study support a central role for CD98 within a multimolecular unit that regulates cell aggregation.

Antibodies↗
PubMed2000

Synthetic peptides of CD66a stimulate neutrophil adhesion to endothelial cells.

Four members of the carcinoembryonic Ag family, CD66a, CD66b, CD66c, and CD66d, are expressed on human neutrophils. CD66a, CD66b, CD66c, and CD66d Ab binding to the neutrophil surface triggers an activation signal that regulates the adhesive activity of CD11/CD18, resulting in an increase in neutrophil adhesion to HUVEC. To identify active sites on the CD66a Ag, molecular modeling was performed using IgG and CD4 as models, and 28 peptides of 14 aa in length were synthesized that were predicted to be present at loops and turns between beta-sheets. The peptides were tested for their ability to alter neutrophil adhesion to HUVEC. Three peptides, each from the N-terminal domain, increased neutrophil adhesion to HUVEC monolayers. This increase in neutrophil adhesion caused by CD66a peptides was associated with up-regulation of CD11/CD18 and down-regulation of CD62L on the neutrophil surface. Scrambled versions of these three peptides had no effect on neutrophil adhesion to the endothelial cells. The data suggest that peptide motifs from at least three regions of the N-terminal domain of CD66a are involved in the interaction of CD66a with other ligands and can initiate signal transduction in neutrophils.

Antigens, CD↗
PubMed2000

CD63 associates with CD11/CD18 in large detergent-resistant complexes after translocation to the cell surface in human neutrophils.

CD63 antibody binding to the neutrophil surface triggers a transient activation signal that regulates the adhesive activity and surface expression of CD11/CD18. Gel permeation chromatography demonstrated that all of the cell surface CD11/CD18 associated with CD63 eluted in the void volume, indicating that they were present in large detergent-resistant complexes. In contrast, the majority of the total cellular CD63, CD11 and CD18, which are largely intracellular, was not present in complexes. The data suggest that intracellular CD11, CD18 and CD63 are not in detergent-resistant complexes, but enter such complexes following translocation to the cell surface.

Antigens, CD↗
PubMed2000

Novel molecular mechanisms of dendritic cell-induced T cell activation.

In this study we have re-examined the molecular mechanisms involved in activation of T cells by dendritic cells (DC). Human peripheral blood DC (PBDC) were derived by 2 h adhesion followed by 7 day culture in a combination of granulocyte macrophage colony stimulating factor and IL-4, and depletion of residual T and B cells. These PBDC were used to induce autologous T cell proliferation in a CD3-dependent response, and antibodies against CD11a/18 and CD86 were used as control inhibitors of accessory function. Antibodies against five of the cell surface molecules that we have recently identified on the surface of DC, CD13, CD87, CD98, CD147 and CD148, and an antibody which recognizes a molecule that has not as yet been identified, all inhibited the CD3-induced T cell proliferation. These findings were observed not only when antibodies were present throughout the culture, but also when they were prepulsed on to the surface of the DC, suggesting the inhibition was mediated via the antigen-presenting cells rather than the T cell. The same set of antibodies also inhibited an allospecific mixed lymphocyte reaction, confirming that the inhibitory effect was not dependent on the use of a CD3 antibody as the stimulating agent. All the antibodies of known specificity inhibited both CD4 and CD8 T cells equally. Unlike CD87, CD98 and CD147 antibodies, which inhibited activation of both CD45RA (naive) T cells and CD45RO (memory) T cells, CD13 and CD148 appeared to be involved in activation of naive cells only. The molecules identified in this study have not previously been demonstrated to play a role as accessory molecules on DC, the cells that are pivotal for immune induction. Therefore they may provide new potential targets for modulation of the immune response at the APC level.

Antibodies, Monoclonal↗
PubMed2000

Inhalational interleukin-2 liposomes for pulmonary metastases: a phase I clinical trial.

The lung is a common site of both metastases and primary neoplasia. This phase I study was designed to test the feasibility and toxicity of administering interleukin (IL)-2 liposomes by aerosol to patients with pulmonary metastases. The goal was to test whether IL-2 liposomes could be given by aerosol using biologically effective but non-toxic doses in an outpatient setting. Liposomes containing IL-2 or placebo (buffer) were synthesized and mixed to provide a constant lipid dose, and were nebulized using a Puritan twin jet nebulizer and a standard compressor. The liposome-containing mist was inhaled for about 20 min 3 times a day in order to selectively stimulate immune function within the lung and to avoid systemic toxicity. The dose chosen was based on canine efficacy and toxicity studies that used bronchoalveolar lavage to demonstrate increased cell numbers and activation of mononuclear cells after inhalation of nebulized IL-2 liposomes. Nine patients were treated in three cohorts of three patients at 1.5, 3.0 and 6.0 x 10(6) IU of IL-2 3 times a day. No significant toxicity was observed. We conclude that the delivery of IL-2 liposomes by inhalation is well tolerated. Further studies of inhalational IL-2 liposomes to determine efficacy as an anti-cancer therapy are warranted.

Administration, Inhalation↗
PubMed1999

Identification of clusterin sequences mediating renal tubular cell interactions.

Expression of the glycoprotein clusterin is markedly increased following tissue injury. One function of clusterin is to promote cell interactions which are perturbed in these pathologic settings. Clusterin causes cell aggregation and adhesion in vitro yet the molecular mechanism for this effect is not known. In order to identify the active site(s) of clusterin, 34 peptides, each 15 amino acid residues in length, were synthesized from hydrophilic regions of human clusterin. When studied individually, none of the peptides caused aggregation of LLC-PK1 cells, a porcine renal epithelial cell line. However, two out of the 34 peptides inhibited clusterin-induced cell aggregation in a dose-dependent manner. Scrambled versions of these two 'active' peptides did not inhibit cell aggregation. Seven peptides promoted cell adhesion. In conclusion, these findings provide evidence for novel amino acid sequences mediating clusterin-induced renal cell interactions.

Animals↗
PubMed1998

Tyrosine kinase activity is associated with CD44 in human neutrophils.

CD44 appears to be involved in signal transduction, however, the mechanism of this function is unclear. Protein kinase activity was detected in neutrophils associated with CD44. Most of the protein kinase activity associated with these antigens was tyrosine kinase activity. Src family kinases lyn and hck were found to account for much of the associated tyrosine kinase activity. The data suggest that associated tyrosine kinase activity may play a role in signal transduction from CD44 in neutrophils to regulate other cell functions.

Humans↗
PubMed1998

Oral glutamine reduces the duration and severity of stomatitis after cytotoxic cancer chemotherapy.

BACKGROUND: Mouth sores and/or difficulty swallowing are common and painful consequences of cytotoxic chemotherapy for cancer. In previous studies oral glutamine was found to protect animals from the effects of whole abdominal radiation and methotrexate-induced enteritis. Glutamine also was found to reduce oral mucositis in a nonrandomized pilot study in humans. Therefore, the authors attempted to determine the efficacy of oral glutamine in a randomized, double blind, crossover trial in cancer patients receiving chemotherapy. METHODS: Twenty-four patients (16 children and 8 adults) received glutamine or placebo (glycine) suspension (2 g amino acid/M2/dose twice daily) to swish and swallow on days of chemotherapy administration and for at least 14 additional days. Patients completed a calendar indicating days of mouth pain associated with each chemotherapy course and the effect of mouth pain on oral intake. RESULTS: Paired data indicated significant amelioration of stomatitis associated with glutamine administration after chemotherapy. The duration of mouth pain was 4.5 days less in chemotherapy courses in which glutamine supplementation was compared with placebo (Wilcoxon's signed rank test, P=0.0005). The severity of oral pain also was reduced significantly when glutamine was provided with chemotherapy (the amount of days mucositis restricted oral intake to soft foods [> or =Grade 2; Modified Eastern Cooperative Oncology Group grading system] was 4 days less with glutamine compared with placebo; Wilcoxon's signed rank test, P=0.002). CONCLUSIONS: Low dose oral glutamine supplementation during and after chemotherapy significantly reduced both the duration and severity of chemotherapy-associated stomatitis. Oral glutamine appears to be a simple and useful measure to increase the comfort of many patients at high risk of developing mouth sores as a consequence of intensive cancer chemotherapy.

Administration, Oral↗
PubMed1998

Association of beta 1 integrin with protein kinase activity in large detergent resistant complexes.

Integrins play a critical role in cell adhesion and mediate cell signaling. This report identifies the association of serine protein kinase activity with the beta 1 integrin by immunoprecipitation and phosphoamino acid analysis techniques. Reprecipitation techniques suggested that the serine kinase activity was not a member of the protein kinase C family. By gel filtration, most of the protein kinase activity associated with beta 1 integrin as well as most of the cell-surface beta 1 integrin was present in large detergent resistant complexes. These results suggest that serine protein kinase activity associated with the beta 1 integrin may play a role in signaling via the beta 1 integrin.

Chromatography, Gel↗
PubMed1998

Subcellular localization of glycosphingolipids in human neutrophils.

The subcellular distribution of five major glycosphingolipids (GSLs) in human neutrophils was analyzed. The neutrophils were isolated from the blood of six donors and subdivided in three fractions containing the cell membranes, and the primary and the secondary granules, respectively. The separation was confirmed with antibodies detecting established subcellular fraction-specific molecules. The two main neutral GSLsGalbeta1-4Glcbeta1-1'Cer (lactosylceramide, LacCer) and nLc4Cer (paragloboside, PG) and the three gangliosides IV3NeuAcnLc4Cer (2-3SPG), IV6NeuAcnLc4Cer (2-6SPG), and VI3NeuAcnLc6Cer (2-3SnHC) were quantitated using the immunochemical digoxigenin (DIG) staining procedure. Secondary granules contained the highest amount of these GSLs. They are followed by the primary granules and the cell membranes. Based on this quantitation, we conclude that the majority of the GSLs of neutrophils occur intracellularly. These findings are in striking contrast to the general assumption of GSLs being mainly concentrated in the cell membrane.

Cell Membrane↗
PubMed1998

CD43 is associated with tyrosine kinase activity in human neutrophils.

CD43 appears to be involved in signal transduction, however, the mechanism of this function is unknown. Protein kinase activity was detected in neutrophils associated with CD43. Most of the protein kinase activity associated with these antigens was tyrosine kinase activity. The src family kinases lyn and hck were found to account for much of the associated tyrosine kinase activity. The data suggest that associated tyrosine kinase activity may play a role in signal transduction via CD43 to regulate other cell functions.

Antigens, CD↗
PubMed1998

Changes in neutrophil surface phenotype during hemodialysis.

The initiation of hemodialysis using cuprophane membranes is followed by a rapid fall in the circulating neutrophil count. This neutropenia is caused by a transient sequestration of neutrophils in the lung due to homotypic aggregation, largely in response to generation of C5a by contact of plasma with the dialyzer. The transient nature of hemodialysis neutropenia is due to desensitization of neutrophils to stimulation by C5a, thus demonstrating desensitization in vivo. To examine the in vivo effects on surface phenotype of continuous exposure of neutrophils to C5a over 3 h, the surface expression of 22 antigens was examined by flow cytometry in patients undergoing dialysis. Neutropenia was prominent at 15 min and absent at 60 and 180 min of dialysis. CD10, CD11b, CD11c, CD13, CD18, CD35, CD45, CD66acde, and CD66b were upregulated at 15 min and remained upregulated at 180 min. CD61 and CD63 increased slightly at 15 min and returned to baseline by 180 min. CD16 and CD62L were down regulated at 15 min and normalized by 180 min. CD15s, CDw17, CD32, and CD44 were slightly down regulated at 15 min and then returned to baseline by 180 min. CD11a, CD15, CD24, CD31, and CDw65 did not change during dialysis. This study demonstrates the changes in surface phenotype of neutrophils during prolonged in vivo exposure to C5a over 3 h, during which time neutrophils become desensitized to subsequent stimulation by similar concentrations of C5a but maintain responsiveness to other chemotactic stimuli.

Adult↗
PubMed1998

Effect of low-dose oral glutamine on painful stomatitis during bone marrow transplantation.

Painful oral mucositis is a common complication after bone marrow transplantation (BMT). Glutamine is a nutrient for rapidly dividing cells and the major energy source for intestinal epithelium. This study tested whether an oral glutamine preparation could decrease the severity of oral mucositis in patients undergoing BMT. Glutamine or a placebo (glycine) were administered from admission until day +28 in 193 BMT patients in a randomized, double-blind, placebo-controlled study at a dose of 1.0 g amino acid/m2/dose swish and swallow four times a day. In autologous BMT patients (n = 87) glutamine was associated with significantly less mouth pain by self report and by opiate use (5.0+/-6.2 days of morphine for glutamine vs 10.3+/-9.8 days for placebo; P= 0.005). Matched sibling BMT patients had no effect by self report and an increased duration of opiate use (23.2+/-5.7 days for glutamine vs 16.3+/-8.3 days for placebo) (P = 0.002). However, day 28 survival of allogeneic patients was improved by glutamine. No significant differences in TPN use, rate of relapse or progression of malignancy, parenteral antibiotic use, acute or chronic GVHD, or days of hospitalization were observed in either autologous or allogeneic recipients. No toxicity of glutamine was observed. We conclude that oral glutamine can decrease the severity and duration of oropharyngeal mucositis in autologous BMT patients but not in allogeneic BMT patients, possibly due to interaction with methotrexate.

Administration, Oral↗
PubMed1998

Mechanism of transient dyspnea induced by pegylated-liposomal doxorubicin (Doxil).

While mucositis and hand-foot syndrome are the main limiting toxicities of pegylated-liposomal doxorubicin, a small proportion of patients develop transient dyspnea at the initiation of drug infusion. Of the first 35 patients in a phase II study of pegylated-liposomal doxorubicin, three developed dyspnea, two low back pain and two pain at the site of tumor, within 1-5 min after starting the pegylated-liposomal doxorubicin infusion. The symptoms resolved within 5-15 min of stopping the infusion. In each case, the infusion was restarted without adverse effect. The mechanism of these symptoms is unclear. Because the dyspnea was reminiscent of that seen with hemodialysis neutropenia, complete blood counts were obtained in four of these patients approximately 2 min after the onset of symptoms. In all four patients, relative neutropenia was present (ANC 35, 3, 24 and 46% of pretreatment) that resolved by the end of the pegylated-liposomal doxorubicin infusion. Pegylated-liposomal doxorubicin stimulated neutrophil adhesion to human umbilical vein endothelial cells in vitro at concentrations predicted to be present in plasma during the initiation of treatment. Thus, pegylated-liposomal doxorubicin can induce an increase in neutrophil adhesion directly. We conclude that one mechanism of pegylated-liposomal doxorubicin-induced acute dyspnea is a transient sequestration of neutrophils in the pulmonary circulation, resulting in a decrease in compliance and associated dyspnea. In the patients in this study, these symptoms were transient, mild and not life threatening. Pegylated-liposomal doxorubicin is generally well tolerated and we do not routinely use premedications in patients receiving pegylated-liposomal doxorubicin.

Adult↗
PubMed1997

CD50 monoclonal antibodies inhibit neutrophil activation.

The constitutive high expression of CD50 (ICAM-3) on resting leukocytes, coupled with the observation that CD50 is the primary LFA-1 ligand on resting T cells, suggests that CD50 may be an important LFA-1 ligand in the initiation of the immune/inflammatory response. CD50 mAbs have been reported to increase homotypic adhesion of lymphocytes, and lymphocyte adhesion to HUVEC and extracellular matrix proteins. In this study, the effects of CD50 mAbs on neutrophil activation were examined. CD50 mAbs were found to inhibit neutrophil adhesion induced by FMLP and 12-O-tetradecanoyl-phorbol-13-acetate to resting and TNF-activated HUVEC. CD50 mAbs also inhibited neutrophil adhesion stimulated by CD66a, CD66b, CD66c, and CD66d mAbs to HUVEC. CD50 mAbs inhibited the up-regulation of CD11b/CD18 to the neutrophil surface, and the down-regulation of surface CD62L expression. The potential contribution of src family kinases to the previously described tyrosine kinase activity associated with CD50 in neutrophils was also examined. hck and lyn were found to account for much of the tyrosine kinase activity associated with CD50 in neutrophils. The data indicate that CD50 in neutrophils functions not only as a potential ligand for LFA-1, but also regulates the surface expression and activity of CD11b/CD18 and CD62L. In contrast to the effects in lymphocytes, CD50 appears to function as a negative regulator of neutrophil activation.

Antibodies, Monoclonal↗
PubMed1997

A phase I study of ambulatory continuous infusion paclitaxel.

Chemotherapy given by continuous infusion may have different toxicity profiles and efficacy than when given by bolus administration. Thirty-one patients with refractory tumors entered a phase I trial in which paclitaxel was administered for 7 days by continuous infusion every 28 days. Only one patient required hospitalization for treatment, because of an initial poor performance status, and most carried out normal activities on an ambulatory basis. After the first three patients, patients were entered in cohorts of five with the starting dose of 120 mg/m2. Each subsequent cohort was begun at a dose 10% higher than the previous cohort. Later courses within each cohort were increased 10% in an individual patient, if toxicity allowed. Nausea was rare. Of 15 patients with a soft tissue sarcoma refractory to doxorubicin, dacarbazine, ifosfamide, and etoposide, there were: one partial response (PR), five stable diseases and eight progressive; one patient was not evaluable for response. The PR occurred in a patient with a very aggressive sarcoma and very bulky disease, and was maintained for more than 1 year. We conclude that paclitaxel given by ambulatory continuous i.v. infusion is well tolerated with a maximally tolerated starting dose of 160 mg/m2.

Adult↗