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Biomedical subjects

R F Holcombe

Publications and source records attributed to R F Holcombe.

At least 37 records · Page 2Linked to original sources
PubMed1996

Lysosome-associated membrane proteins h-LAMP1 (CD107a) and h-LAMP2 (CD107b) are activation-dependent cell surface glycoproteins in human peripheral blood mononuclear cells which mediate cell adhesion to vascular endothelium.

Lysosome-associated membrane proteins (LAMPs) are transmembrane lysosomal glycoproteins which are detectable at the cell surface of lymphocytes in patients with scleroderma and systemic lupus erythematosus. While these proteins have been shown to mediate adhesion of tumor cells to vascular endothelial selectins, the function of LAMPs expressed at the cell surface of peripheral blood lymphocytes has not been previously examined. In the present study, the role of lamp2 (CD107b) in lymphocyte adhesion to vascular endothelium and the factors which influence in vitro cell surface expression of both lamp1 (CD107a) and lamp2 (CD107b) are examined. Freshly isolated PBMCs and unstimulated PBMCs in the culture had low levels of cell surface lamp1 and lamp2 expression which were significantly increased following PHA stimulation (P < 0.0001). A dose-dependent response to PHA and the effect of varying concentrations of serum were defined. Kinetic analysis revealed that the majority of the increase in both lamp1 and lamp2 occurred within the first 2 hr of incubation and that a subset of PBMCs maintained expression for at least 96 hr. Incubation of cells with colchicine and cycloheximide modified the cell surface expression of these proteins. Interleukins 2, 4, 6, and 8 had only a modest effect on the degree of cell surface lamp1 and lamp2 expression, though they did significantly affect the distribution of expression among different subtypes of lymphoid cells. Under the conditions utilized in this study, cell surface LAMP expression was confined primarily to CD56+ cells and to CD3+ cells. Functional analysis utilizing a fluorescence-based adhesion assay revealed that cell surface lamp2 mediates adhesion of PBMCs to vascular endothelium, possibly by interacting with endothelial selectins. LAMPs likely contribute to the migration of activated leukocytes to sites of inflammation in vivo.

Adult↗
PubMed1996

Positional cloning of the Chediak-Higashi syndrome gene: genetic mapping of the beige locus on mouse chromosome 13.

BACKGROUND: Chediak-Higashi syndrome (CHS) is a systemic disorder of human and mouse (beige, bg) that is characterized by aberrant intracellular protein kinesis and lysosomal trafficking. Affected individuals exhibit a severe primary immune deficiency that principally affects the function of granulocytes and cytolytic lymphocytes and partial oculocutaneous albinism, platelet dysfunction, and neurodegeneration. Chediak-Higashi syndrome is inherited as an autosomal recessive Mendelian trait in human and mouse and maps on proximal mouse Chromosome 13. METHODS: To clone positionally the defective gene in CHS, we have generated a large number of backcross mice who segregate for beige. Genomic DNA from these mice was genotyped for 26 genetic markers known to map on proximal mouse Chromosome 13. RESULTS: By segregation analysis, bg was localized to a 0.24 centiMorgan interval and was shown to cosegregate with 6 genetic markers (Nid, Estm9, D13Mit56, D13Mit162, D13Mit237, and D13Mit240). Two of these loci, Nid and Estm9, are genes and represent candidates for bg. Nidogen (Nid) encodes an extracellular matrix protein that is a component of basement membranes. Estm9 is a sequence that is transcribed ubiquitously in mouse embryos and encodes a protein of unknown function. Mutation analysis of Nid and Estm9 was undertaken in 6 bg alleles; no differences were observed between bg and coisogenic controls by analysis of Northern blots, Southern blots, or by quantitative reverse transcription and polymerase chain reaction. CONCLUSIONS: These studies indicate that a genomic rearrangement affecting Nid or Estm9 does not underlie bg. The bg locus has been localized on mouse Chromosome 13 with sufficient precision to enable rapid cloning of the bg non-recombinant interval and eventual identification of the gene for Chediak-Higashi syndrome among sequences within the interval.

Animals↗
PubMed1995

Quantitation of CD62, soluble CD62, and lysosome-associated membrane proteins 1 and 2 for evaluation of the quality of stored platelet concentrates.

BACKGROUND: Platelets become activated during storage, which results in secretion of granules, vesiculation of microparticles, secretion of protein, and a number of other biochemical and morphologic processes that decrease the utility of platelet concentrates stored for transfusion. STUDY DESIGN AND METHODS: To evaluate the quality of stored platelet concentrates, the cell surface expression of specific activation-dependent antigens (CD62 and lysosome-associated membrane proteins 1 and 2 [LAMP-1, LAMP-2]) on platelets stored in a hospital blood bank over a 7-day period was examined. Relative microparticle counts and the expression of CD62 by microparticles, as well as platelet concentrate supernatant levels of soluble CD62, were determined. RESULTS: The percentage of platelets expressing CD62 increased significantly from Day 1 to Day 5 (p < 0.05) of storage; the mean fluorescence values for CD62 did not. In contrast, the mean fluorescence values of LAMP-1 and LAMP-2 rose significantly (p < 0.01 and p < 0.05, respectively) between Days 1 and 5. Significant declines in CD62, LAMP-1, and LAMP-2 percent expression and mean fluorescence were seen on Day 6 of storage (p < 0.001). Microparticle numbers increased significantly during storage and correlated with levels of CD62 protein (free and membrane-bound) (r = 0.95 vs. Day 2, p < 0.05; r = 0.88 vs. Day 5, p < 0.05). CONCLUSION: Flow cytometric evaluations of the expression of cell surface CD62, LAMP-1, and LAMP-2 are complementary tests that, especially when used in conjunction with the quantitation of CD62 protein, provided a simple and effective means of evaluating the quality of platelet concentrates stored for transfusion.

Antigens, CD↗
PubMed1995

Cell surface expression of lysosome-associated membrane protein-2 (lamp2) and CD63 as markers of in vivo platelet activation in malignancy.

Platelets may become activated in vivo in a number of prethrombotic conditions including cancer. In the present study, cell surface expression of lysosome-associated membrane protein-2 (lamp2) and CD63 (lamp3) were examined by flow cytometry in 15 healthy volunteers and 5 patients with metastatic cancer to determine their utility as markers of in vivo platelet activation. Unstimulated platelets from controls had low levels of lamp2 expression, in contrast to cancer patients, who had significantly elevated levels (3.79 +/- 1.48% vs 33.9 +/- 5.6%). Upon stimulation with collagen, a greater than two-fold increase in the number of platelets expressing detectable levels of lamp2 was seen only among controls and not in cancer patients. Stimulation with collagen also resulted in a nearly two-fold increase in the proportion of platelets expressing CD63 in the control group, and a less than 1.5-fold increase in CD63 was seen in the patient group. The results suggest that cell surface lamp2 and CD63, like cell surface expression of GMP-140, may be good indicators of in vivo platelet activation and may be potentially useful in identifying patients with prethrombotic disorders.

Adenosine Diphosphate↗
PubMed1995

Natural killer cells and gamma delta T cells in scleroderma: relationship to disease duration and anti-Scl-70 antibodies.

OBJECTIVES: To examine the expression of the natural killer (NK) antigen CD56, and T cell receptor delta chain antigen (TCR delta), expressed on the gamma delta T cell subset, in patients with scleroderma, and to correlate levels of expression with clinical characteristics. METHODS: Peripheral blood mononuclear cells (PBMCs) from 15 patients with scleroderma and 11 controls were obtained from heparinised blood on a ficoll/hypaque gradient, stained with monoclonal antibodies, and examined by flow cytometry for expression of CD56 and TCR delta. RESULTS: Overall, the proportion of PBMCs expressing CD56 in the patient group (14.4 (SEM 2.6)%) was not significantly different from controls (8.75 (2.6)%). The greatest levels of expression were found in patients late (more than three years) in their disease course (18.1 (3.3)%) and in patients who did not express anti-Scl-70 antibodies (17.1 (3.5)%). The proportion of gamma delta T cells was significantly lower in the patient group (1.61 (0.52)% v control 2.61 (0.46)%) (p < 0.05). Patients early in their disease or with anti-Scl-70 antibodies accounted for the reduction in gamma delta T cells (0.71 (0.29)% and 0.96 (0.41)% (p < 0.01 and p < 0.05, respectively). CONCLUSIONS: This study emphasis that NK and gamma delta T cell numbers vary depending upon patient characteristics and may help explain prior contradictory reports. Decreased numbers of gamma delta T cells were seen in scleroderma patients, especially those with anti-Scl-70 antibodies and a disease duration of less than three years.

Adult↗
PubMed1995

Phase II study of fluorouracil and its modulation in advanced colorectal cancer: a Southwest Oncology Group study.

PURPOSE: A variety of fluorinated pyrimidine-based regimens for the treatment of disseminated colorectal cancer have been presented in the medical literature. The Southwest Oncology Group designed a screening trial of seven regimens of fluorouracil (5-FU) to assess efficacy and toxicity afforded by biochemical modulation or schedule variations. PATIENTS AND METHODS: Six hundred twenty patients were entered into this trial between August 1989 and January 1993. Eligible patients were classified as having recurrent or disseminated disease that was measurable or nonmeasurable. All eligible patients were evaluated for toxicity and survival; patients with measurable disease were evaluated for response according to standard criteria. RESULTS: No regimen achieved a higher response rate than single-agent bolus 5-FU. Eighty-four percent of patients have been monitored until death. The median survival time for the entire cohort is 14 months. Survival hazards ratios showed a positive trend in favor of the unmodulated infusion regimens, while high-grade toxicities occurred more frequently in the 5-FU bolus arms. The major high-grade toxicities were granulocytopenia and diarrhea. CONCLUSION: In this trial, no regimen provided substantial improvement relative to 5-FU bolus or single-agent therapy for either response or survival in the treatment of disseminated colorectal cancer. The single-agent infusion regimens demonstrated the most encouraging results with a favorable toxicity profile and a 2-month longer survival duration than 5-FU bolus therapy.

Adult↗
PubMed1994

Alteration in lymphocyte phenotype associated with administration of adjuvant levamisole and 5-fluorouracil.

Levamisole (LMS) and 5-fluorouracil (5FU) administered adjuvantly are effective in reducing the relapse rate following surgical resection of Duke's stage C colon carcinoma. It has been postulated that LMS acts to stimulate the immune system and that this is one mechanism through which this drug exerts its antitumor effects. In this study, peripheral blood mononuclear cells (PBMC) were analyzed in nine patients with surgically resected colon carcinoma prior to initiation of adjuvant LMS/5FU and at several subsequent times while patients were on therapy. Changes in lymphocyte phenotype and soluble interleukin-2 receptor (sIL-2R) between pre-study samples and samples obtained during adjuvant LMS/5FU were evaluated. Significant increases were seen in the proportion of PBMC expressing natural killer (NK) antigen CD56 (14.7 +/- 2.4% versus 18.1 +/- 2.6%; P < 0.05) and surface IL-2R (CD25; 0% versus 0.42 +/- 0.15%; P < 0.05), in sIL-2R (314 +/- 86 U/ml versus 736 +/- 173 U/ml; P < 0.05), and in the CD4:CD8 ratio (2.34 +/- 0.93 versus 3.47 +/- 1.23; P < 0.01). A significant decrease in the proportion of CD8+ PBMC (24.7 +/- 3.8% versus 18.8 +/- 2.6%; P < 0.01) and total CD8+ PBMC (537 +/- 118 versus 324 +/- 37; P < 0.01) was seen. The increase in CD56+ cells correlated with sIL2R levels (r = 0.46; P < 0.05). No changes were noted for CD3, CD4, CD5, CD14, CD16, CD19, CDw49a, or TCR delta. The greatest increase in CD56+ cells and the smallest reduction in CD8+ cells were seen in the subgroup of patients who remained disease-free following adjuvant chemotherapy. This study suggests that adjuvant LMS/5FU has significant stimulatory effects on the immune system, which correlate with patient outcome and may account at least in part for its clinical efficacy.

Antigens, CD↗
PubMed1994

Social drinking and the immune response: impairment of lymphokine-activated killer activity.

The effect of limited and intermittent alcohol ingestion on the immune response in humans has not been extensively studied. The authors, in this study, evaluate peripheral blood mononuclear cell cytotoxicity before and after alcohol ingestion in a setting designed to mimic social drinking. Eleven healthy volunteers consumed two 12 oz (355 mL) cans of beer in 30 minutes while eating pizza. Five control individuals ingested non-alcoholic beverages. Natural killer and lymphokine-activated killer activity were determined for peripheral blood mononuclear cells obtained before and 30 minutes after alcohol ingestion. Interleukin 2-induced lymphokine-activated killer activity was significantly reduced in blood samples obtained after alcohol ingestion when compared with pre-alcohol samples (p < 0.01). Natural killer activity (unstimulated) was not affected by alcohol ingestion. The authors demonstrate that ingestion of a small amount of alcohol impairs the cytotoxic capacity of peripheral blood mononuclear cells. Alcohol in the context of social drinking may have deleterious effects on the immune system's ability to clear virus-infected cells or cells that have undergone neoplastic transformation, especially for individuals with pre-existing immunosuppression.

Adult↗
PubMed1994

The role of the hematologist/oncologist as a primary care provider.

To determine the role of the hematologist-oncologist as a primary care provider, a survey was administered to a consecutive sample of 238 hematology-oncology patients. Patients were selected at random from the outpatient hematology-oncology clinics at three institutions: 66.1% from a university medical center, 22.5% from a private hospital, and 11.4% from a health maintenance organization-affiliated clinic. A total of 73 (30.9%) respondents reported they would see their hematologist-oncologist (heme/onc) for routine illnesses, such as sinus or bladder infections. Of the respondents who did not have a family doctor, the percentage increased to 45.5%. Of those patients who had other medical problems, such as hypertension or diabetes, 46 (43.0%) were followed by their heme/onc for these other medical problems. If the respondent did not have a family doctor, the percentage increased to 66.0%. Patients at the university medical center more frequently did not have a family doctor and used their heme/onc for primary care to a greater degree than patients at the private hospital and health maintenance organization (HMO)-affiliated clinic. A total of 55.9% of the respondents reported having the best physician-patient relationship with their heme/onc, whereas only 8.5% had the best relationship with their family doctor. The heme/onc does provide primary care for their patients. If the patient does not have a family doctor, the amount of primary care administered by the heme/onc greatly increases. It is likely that patients rely on their heme/onc for this care because of the close physician-patient relationship that develops as a result of the frequent clinic visits required by many patients with cancer or blood disorders.

Hematology↗
PubMed1994

Correlation of serum interleukin-8 and cell surface lysosome-associated membrane protein expression with clinical disease activity in systemic lupus erythematosus.

Cell surface expression of lysosome-associated membrane proteins (LAMPs) correlates with serum interleukin-8 (IL-8) levels, shorter disease duration, greater functional impairment from disease-related symptoms and soluble IL-2 receptor levels (sIL-2R) in patients with scleroderma. In this study of 46 patients with systemic lupus erythematosus (SLE), the relationship of serum IL-8 and cell surface LAMP to two clinical measures of disease activity, the SLEDAI and SLAM scales, was evaluated. IL-8 levels were determined on serum samples by the immunometric sandwich enzyme immunoassay technique. Cell surface LAMP expression was determined by flow cytometric quantitation of peripheral blood mononuclear cells with monoclonal antibodies directed against two of the major LAMP proteins, lamp1 and lamp2. The clinical disease activity scales correlated significantly with each other, with C3 levels, serum IL-8, C4, dsDNA and sIL-2R. Lamp1 and lamp2 expression correlated with the SLAM but not the SLEDAI scale. Serum IL-8 levels were elevated in 49 of 51 samples tested (44 of 46 patients) and had a stronger correlation with disease activity than C4, dsDNA and sIL-2R levels. Significantly higher levels of IL-8 were seen in patients with evidence of renal involvement. Serum IL-8 and cell surface LAMP expression may be useful indicators of disease activity in patients with SLE. The possible role of IL-8 in the pathogenesis of SLE requires further investigation.

Adolescent↗
PubMed1994

Clinical applications of the interleukins: present and future.

Clinical use of biologic agents, especially in the fields of hematology and oncology, is becoming increasingly common. Many agents, interferon-alpha, interferon-gamma, granulocyte and granulocyte-monocyte colony stimulating factors, erythropoietin, and interleukin-2 have already been approved for clinical use. Others are currently in clinical trials or will soon be available for administration to humans. This review summarizes the properties of interleukins 1 through 12, their derivation, activities, and approved or potential clinical uses.

Adult↗
PubMed1994

Lysosomal enzyme activities in Chediak-Higashi syndrome: evaluation of lymphoblastoid cell lines and review of the literature.

Chediak-Higashi syndrome (CHS) is an inherited immunodeficiency disorder characterized by giant lysosomal granules in all granule-containing cells. Prior examination of lysosomal enzyme activities in granulocytes and other cells derived from patients with CHS have revealed multiple abnormalities, with the predominant finding being diminished activity of many of the enzymes tested. Abnormalities in lysosomal enzyme activity are also found in animal models of CHS (cattle, aleutian mink, and beige mice). In this study, we have examined lymphoblastoid cell lines derived from a patient with CHS and from an individual heterozygous for the CHS gene for acid phosphatase, beta-glucuronidase, and alpha-mannosidase activity. These cell lines have recently been shown to be satisfactory in vitro models for the disease. Acid phosphatase activity was increased in the heterozygous-derived cell line when compared to control while other enzyme activities were normal both in the CHS- and heterozygous-derived cell lines. We have reviewed the literature and summarized published abnormalities of lysosomal enzyme activities in humans and animals with CHS.

Acid Phosphatase↗
PubMed1993

Effect of levamisole on major histocompatibility complex class I expression in colorectal and breast carcinoma cell lines.

BACKGROUND: The antihelminthic drug levamisole (LMS) is used in conjunction with 5-fluorouracil (5-FU) as adjuvant therapy to reduce the incidence of colon cancer relapse following surgical resection. Clinical trials in patients with breast cancer have yielded conflicting results as to its efficacy in the treatment of this malignancy. LMS is thought to act as an immunostimulant, yet its precise mechanism remains unclear. In this study, the effect of LMS on major histocompatibility complex (MHC) class I (MHC I) and MHC class II (MHC II) expressions in human colorectal and breast carcinoma cell lines was examined. METHODS: The colon cancer cell line CaCo-2 and the breast cancer cell line MDA-MB-435 were cultured for 24-68 hours in the presence or absence of 10-microns LMS followed by staining with antibodies directed against either MHC I or MHC II: After staining, cells were visualized by fluorescent microscopy. RESULTS: When cultured in the presence of LMS, cells from both cell lines exhibited a decreased fluorescent intensity with antibodies directed against MHC I protein. The most significant difference from cells cultured without LMS was apparent after 48 hours of incubation. Neither cell line exhibited fluorescent intensities above background when stained with anti-MHC II antibody. CONCLUSIONS: LMS decreases the expression of MHC I on CaCo-2 and MDA-MB-435 tumor cell lines. Prior studies have indicated that natural killer (NK) cells are more efficient in attacking cells with lowered or no MHC I expression. An MHC I deficiency induced by LMS would augment NK-mediated immune surveillance. One mechanism contributing to levamisole's anti-tumor activity in vivo may be reduction of MHC I expression on tumor cells.

Antibodies, Monoclonal↗
PubMed1993

Cell surface expression of lysosome-associated membrane proteins (LAMPs) in scleroderma: relationship of lamp2 to disease duration, anti-Sc170 antibodies, serum interleukin-8, and soluble interleukin-2 receptor levels.

Lysosome-associated membrane proteins (LAMPs) are integral transmembrane proteins densely expressed on lysosomes which can be shuttled to the plasma membrane during cell activation. The objective of this study was to examine the expression of LAMPs on the cell surface of peripheral blood mononuclear cells (PBMCs) derived from patients with scleroderma. Heparinized blood was obtained from 23 patients with scleroderma and 15 healthy controls and PBMCs were isolated via a Ficoll gradient. Cells were stained with monoclonal antibodies directed against two of the major LAMPs, lamp1 and lamp2, and after subsequent staining with a fluorescent second antibody, were analyzed by flow cytometry. Two -and three-color immunofluorescence was utilized to define the phenotype of LAMP+ cells. The proportion of PBMCs expressing lamp2 on the cell surface was significantly elevated in patients with scleroderma (2.21 +/- 0.38%) compared to controls (1.14 +/- 0.27%; P < 0.05). Multivariate analysis of patient subgroups indicated that the significant factors contributing to higher levels in patients were shorter duration of disease (P < 0.01) and greater functional disability related to disease manifestations (P < 0.01). Patients with anti-Scl70 antibodies had the highest levels of cell surface lamp2 expression (4.19 +/- 0.90%; P < 0.0005). The degree of cell surface lamp2 expression correlated with the level of sIL2R in 19 scleroderma patients (r = 0.48; P < 0.05). Serum IL4 and IL6 did not correlate with cell surface LAMPs or sIL2R. Five of 19 patients had detectable serum levels of interleukin-8 (IL8). These patients had significantly higher cell surface lamp2 expression than those with no detectable IL8 (3.76 +/- 0.48% vs 1.44 +/- 0.39%; P < 0.01). Extended phenotyping revealed that > 85% of lamp2+ cells expressed the B-cell antigen CD19. Cell surface lamp2 expression correlates with clinical and laboratory parameters in scleroderma patients and may reflect immune system activation. Additionally, this is the first report describing an elevation of serum IL8 in an autoimmune or collagen-vascular disease.

Adolescent↗
PubMed1993

Effect of insurance status on pain medication prescriptions in a hematology/oncology practice.

To determine whether insurance status (payer class) affects the amount and type of pain medication prescribed, and whether patients in those groups without prescription drug coverage received lower-cost medications, a case-control study with retrospective chart review was initiated in a university-based hematology/oncology practice in northwest Louisiana. Charts of 710 active patients among all insurance groups (private insurance, Medicare, Medicaid, State Hospital System) were analyzed to determine insurance status, pain medication (amount and type), and diagnosis. The proportion of Medicaid patients receiving pain medications was significantly increased in relation to their representation in the practice when compared with Medicare patients, patients with private insurance, uninsured patients whose health care costs were provided by the State Hospital System, and the overall patient population. Medicaid patients, especially those with solid tumor malignancies, received the most expensive class of pain medications at a significantly higher rate than other patients. In the studied population of hematology and oncology patients, there is a significant difference in the amount and type of pain medications prescribed between patients with prescription drug coverage (Medicaid) and those without (all other groups including those covered by the statewide system). We propose that consideration be given to alternative methods of financing prescription medications for medically indigent patients.

Academic Medical Centers↗
PubMed1993

Transfusion therapy in sickle cell disease patients: methods and acute indications.

Management of transfusion therapy in sickle cell disease patients with acute complications is often made difficult because of confusing indications, a variety of methods, disparate goals, and varying needs for maintenance transfusion. In priapism, acute chest syndrome, many major surgical procedures, toxemia of pregnancy, and cerebrovascular accidents, the target hemoglobin A level should be made as close to 100% as possible by mechanized red blood cell exchange. If mechanized exchange is unavailable, manual exchange should be instituted. Hemoglobin A should be maintained at greater than 60% to 70% by periodic simple transfusion until patients are fully recovered. Stroke patients should undergo maintenance transfusions for at least 3 years and perhaps 5 to 12 years. Physicians and patients should be aware of the transfusion-related risks of hepatitis and HIV infection. Alloimmunization and iron overload should be minimized in patients requiring frequent transfusions and chelation therapy should be utilized for iron overload.

Anemia, Sickle Cell↗