Search PubMed⌕ Search

Biomedical subjects

G S Nash

Publications and source records attributed to G S Nash.

35 records · Page 2Linked to original sources
PubMed1982

A rapid miniaturized solid-phase radioimmunoassay technique for secreted immunoglobulins, employing microtiter plates, antibody bound to polyacrylamide beads, and filter strip harvesting.

We have developed a solid-phase radioimmunoassay technique, which allows a large number of samples to be assayed, while minimizing amounts of reagents and technician time. The assay is run in microtiter plates, which results in improved organization, shorter assay set-up time and advantageous miniaturization. On the first day only 3 reagents are required: sample or standard, a 125I-labeled antigen, and an antibody attached to a polyacrylamide bead. After on overnight incubation period, the assay is harvested using a commercial microharvesting apparatus (24 samples/2 min) and placed directly into a gamma counter for counting. In the present study, we have developed the assay to measure secreted IgG, IgM and IgA, and we have compared our results with those of a standard radioimmunoassay technique. This rapid, simple, economical approach should be applicable to the radioimmunoassay of other substances as well.

Acrylic Resins↗
PubMed1982

Marked in vitro spontaneous secretion of IgA by human rib bone marrow mononuclear cells.

Mononuclear cells (MNC) isolated from bone marrow curettaged from human ribs spontaneously produced significant amounts of Iga in 14-day in vitro culture. When culture supernatants were tested for each immunoglobulin isotype by radioimmunoassay at days 7, 14, 21, and 28, the peak of spontaneous IgA production was reached by day 14. Culturing marrow MNC in the presence of the polyclonal activator pokeweed mitogen (PWM) ablated this spontaneous IgA activity, and did not stimulate the production of IgG or IgM. In contrast, peripheral blood MNC produced significant amounts of all three immunoglobulin isotypes studied in the presence of PWM, but minimal immunoglobulin spontaneously. PWM stimulated both marrow and peripheral blood MNC to proliferate as demonstrated by increased DNA synthesis. In view of the opposite effects of PWM on immunoglobulin production by peripheral blood and bone marrow MNC, PWM may be stimulating a different functional or developmental subpopulation of cells in each case. We conclude that the bone marrow is a major site of IgA production in the human, that cells within the bone marrow have a blastogenic response to PWM in vitro, and that spontaneous production of IgA by human marrow MNC is inhibited by PWM.

Antibody-Producing Cells↗
PubMed1980

Ionophore-A23187-induced cellular cytotoxicity: a cell fragment mediated process.

Calcium ionophore A23187 was found to induce human white blood cells to kill human red blood cells. Optimal conditions for ionophore-induced cellular cytotoxicity (IICC) included an 18 h time period, an incubation temperature of 25 degrees, a 25:1 or 50:1 killer:target cell ratio,and a final ionophore concentration of 2 . 5 microgram/ml. WBC or granulocytes which were either frozen and thawed three times or sonicated were capable of mediating IICC. As intact cells, granulocytes (67 . 2% cytotoxicity), monocytes (34 . 8%), B cells (22 . 0%) and Null cells (19 . 3%) were effector cells but T cells (7 . 4%) were not. After fragmenting these cells, all cell types including T cells were able to mediate IICC. When cell lines (K562, Chang, and NCTC) were used as effectors, none would mediate IICC when intact. After freezing and thawing, Chang and NCTC would not mediate IICC, whereas K562 cells did. These studies may be indicative of a calcium-dependent, membrane-localized mechanism in cellular cytotoxic processes, and may provide a useful indicator system for isolation of the enzyme systems involved in cellular cytotoxicity.

Anti-Bacterial Agents↗
PubMed1980

Further evidence that antibody-dependent and spontaneous cell-mediated cytotoxicity are mediated by different processes or cell types.

We have observed that canine peripheral blood mononuclear cells are ineffective as mediators of spontaneous cell-mediated cytotoxicity (SCMC) despite being excellent mediators of antibody-dependent cellular cytotoxicity (ADCC). Canine lymphocytes were unable to kill seven cell lines in SCMC assays including Chang, K-562, dog kidney, and foetal intestine. One the other hand, they were able to kill Chang and K-562 cell line cells as well as chicken red blood cells in ADCC assay systems. Canine mononuclear cells were 40% E-rosette forming, 30% surface immunoglobulin bearing, 14% Fc receptor bearing, and 13% esterase staining. K-562 cell line cells inhibited the capability of human peripheral blood cells but not canine peripheral blood cells to kill CRBCs in an ADCC assay. Fc-receptor bearing human lymphocytes of both T-cell and null-cell subclasses mediated both SCMC and ADCC, while Fc-receptor bearing canine lymphocytes mediated ADCC but not SCMC. These observations add to the evidence of a dichotomy between SCMC and ADDC with regards to either cell type or cell processes.

Animals↗
PubMed1980

Alteration of lymphocyte function due to anesthesia: in vivo and in vitro suppression of mitogen-induced blastogenesis by sodium pentobarbital.

The mechanism of decreased lymphocyte responsiveness after major surgery is unclear. Because sodium pentobarbital, and intermediately long-acting barbiturate, will reproducibly induce anesthesia in experimental animals, we utilized a canine model to investigate its effect on lymphocyte proliferation induced by the mitogenic lectins erythroagglutinating phytohemagglutinin (E-PHA) and leukoagglutinating phytohemagglutinin (L-PHA). Although no effect was observed at 10 minutes or 1 hour after an anesthetic dose of sodium pentobarbital, after 1 and 3 hours of anesthesia, canine lymphocytes were significantly suppressed, as demonstrated by decreased responsiveness to E-PHA and L-PHA mitogen stimulation. After 3-hours the majority of animals had mitogenesis values of less than 50% of the preanesthetic control values. Recovery, as measured by a return to at least 70% of the preanesthetic mitogenesis value, was noted in the majority of animals at 24, 48, and 72 hours. In order to investigate the machanisms of the in vivo capability of sodium pentobarbital to induce immunosuppression of lymphocyte transformation, in vitro studies were carried out. Sodium pentobarbital was found to significantly inhibit mitogen-induced canine mononuclear cell blastogenesis at anesthetic (1.5 to 3.0 mg%) drug concentrations in vitro. Lymphocytes pretreated with barbiturate and washed prior to plating did not show this inhibiting effect. Our findings suggest that depression of the immune response reported in patients after operation could result from short-acting barbiturates administered during the induction phase of clinical anesthesia. Furthermore, the suppression may involve in vivo metabolism of pentobarbital, hormones or other in vivo factors, since washed lymphocytes from the in vivo but not the in vitro experiments demonstrated suppression. These results indicate that anesthesia may be an important factor in the immunosuppression reported after major surgery.

Animals↗
PubMed1979

Antibody-dependent cell-mediated antibacterial activity of human mononuclear cells. I. K lymphocytes and monocytes are effective against meningococi in cooperation with human imune sera.

In cooperation with human heat-inactivated antisera from adults immunized with group C meningococcal polysaccharide, normal human peripheral blood mononuclear cells significantly decreased the viability of group C meningococci (Mgc) in vitro. K lymphocytes (Null cells) and monocytes, (but not T or B lymphocytes) were capable of effecting antibody-dependent cell-mediated (ADC) antibacterial activity in this system. The degree to which meningococcal viability was decreased was a function of the length of the test incubation, the concentration of effector cells, and the amount of antiserum used in the assay. When specific antibodies directed against Mgc were adsorbed from the antiserum, cell-mediated antibacterial activity was abolished. ADC antibacterial activity was also abrogated by performing the assay at 4 degrees C or by heating effector cells to 46 degrees C for 15 min before the assay, Similarities between the ADC antibacterial system and previously described ADCC assays are discussed. The data suggest the K cells (as well as monocytes) may play a role in host immune defense against pathogenic bacteria.

Antibodies, Bacterial↗
PubMed1977

Leukemic reticuloendotheliosis: "hairy cell leukemia," functional and structural features of the abnormal cell in a patient with profound leukocytosis.

The development of profound leukocytosis in a patient with leukemic reticuloendotheliosis (LRE) enabled us to obtain purified LRE cells for the investigation of their structural and functional characteristics. The LRE cells of our patient bore surface immunoglobulin and had complement receptors but did not bear Fc receptors and did not form rosettes with sheep erythrocytes. By electron microscopy, the cells were observed to contain typical ribosome lamella structures and to phagocytize both 0.81 micron latex particles and complement-coated zymosan particles. They were adherent to both glass and nylon wool fibers. The mitogenic response to erythroagglutinating phytohemagglutinin was normal to magnitude but delayed chronologically. The binding of 125I-labeled plant lectins was used to characterize the surface topography of LRE cells. Results of these studies indicated that the LRE cell surface differed significantly from the surface of normal T and B lymphocytes and chronic lymphatic leukemia cells. The LRE cells were capable of both stimulating and responding in a one-way mixed lymphocyte culture. However, the LRE cells were not active as effector cells of either cell-mediated lympholysis, a T cell function, or antibody-dependent cellular cytotoxicity, a null cell function. In contrast, they were effector cells of lectin-induced cellular cytotoxicity showing that they did possess the capacity to function as cytotoxic effector cells. These data indicated that the LRE cells in our patient had surface and functional characteristics of both lymphocytes and monocytes.

Binding Sites↗
PubMed1977

Excretion of DNA by purified human lymphocyte subpopulations.

A large proportion of DNA synthesized in vitro by human lymphocytes stimulated with plant mitogens or specific antigens is selectively excreted from the cells. To determine if DNA excretion differs among various types of lymphocytes, we examined purified human lymphocyte subpopulations for DNA synthesis and excretion in response to stimulation by L-PHA. The relative proportion of newly synthesized DNA that is excreted by unseparated mononuclear cells, macrophage-depleted cells, T, and B lymphocytes is identical despite great differences in the magnitude of their responses. Low levels of both DNA synthesis and excretion by macrophage-depleted cells and B cells can be increased by reconstitution with macrophages and T cells, respectively. These data indicate that DNA exretion is a general property of lymphocytes stimulated to undergo DNA synthesis by plant mitogens.

Antigens↗
PubMed1976

Prearmed effector cells and the target cell specificity of lectin-induced cellular cytotoxicity.

We have investigated mechanisms by which plant lectins induce human peripheral blood mononuclear cells to kill red blood cells (RBC) from different species selectively. Cytotoxicity was induced by both mitogenic components of phytohemagglutinin-P (PHA), erythroagglutinating (E-PHA) and leukoagglutinating (L-PHA), and the nonmitogenic lectin wheat germ agglutinin (WGA). The target cells used in an overnight chromium release assay included human autologous RBC, human allogeneic RBC, and xenogeneic RBC from sheep or chickens. Although E-PHA induced cytotoxicity for all cell types, L-PHA caused human mononuclear cells to kill only xenogeneic RBC and, conversely, WGA induced killing of only human RBC. These differences allowed further investigation of possible control mechanisms. The target cell specificity associated with lectin-induced cellular cytotoxicity did not correlate with lectin binding to, or agglutination of, the different red blood cell types. Furthermore, preincubation of RBC with lectins followed by washing did not result in cytotoxicity. However, when the mononuclear cells were preincubated with the lectins, the same cytotoxic specificity was observed as when lectins were present during the entire assay. These experiments suggest that the target cell specificity observed with lectin-induced cellular cytotoxicity is related to a prearmed lymphocyte which seeks out and kills the appropriate target cell.

Animals↗
PubMedDate not supplied

Antibody secretion by human intestinal mononuclear cells from normal controls and inflammatory bowel disease patients.

Inflammatory bowel disease (IBD) intestinal mononuclear cells (MNC) exhibit decreased spontaneous IgA secretion with an increased percentage of monomeric IgA and IgA subclass 1 in both ulcerative colitis and Crohn's disease patients. When compared with control intestinal MNC, a marked increase in spontaneous secretion of IgG is observed from IBD MNC. The greatest increase in spontaneous IgG secretion is seen with ulcerative colitis intestinal MNC, due to the secretion of large amounts of IgG subclass 1. Crohn's disease intestinal MNC have increased IgG subclass 2 secretion. Similar differences in IgG subclass concentrations also occur in the sera of active, untreated, IBD patients. Therefore, major alterations occur with regard to spontaneous antibody secretion of IgA and IgG subclasses in IBD. Because intestinal MNC comprise a unique immunologic compartment, it will be important to better understand the regulatory mechanisms, effector capabilities, and inducing antigens involved in intestinal IgA and IgG subclass secretion in IBD.

Antibody Formation↗