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Biomedical subjects

G M Taylor

Publications and source records attributed to G M Taylor.

At least 109 records · Page 6Linked to original sources
PubMed1988

Down's syndrome lymphoid cell lines exhibit increased adhesion due to the over-expression of lymphocyte function-associated antigen (LFA-1).

We have analysed homotypic adhesion induced by the phorbol ester TPA in EBV-immortalized Down's syndrome (trisomy 21) and normal lymphoblastoid cell lines. Our results show that the trisomy 21 cells aggregated more readily than normal cells. The aggregation of the two types of cell was blocked effectively by the addition of monoclonal antibodies to the alpha and beta chains (CD11a, CD18) of lymphocyte function-associated antigen (LFA-), but not by monoclonal antibodies to LFA-3 and the alpha chain of p150,95 (CD11c). Since TPA did not increase the expression of CD18 on trisomy 21 cells, we conclude that the increased adhesiveness is the result of over-expression of CD18 as a result of gene dosage.

Antibodies, Monoclonal↗
PubMed1988

The expression of CD18 is increased on Trisomy 21 (Down syndrome) lymphoblastoid cells.

The monoclonal antibody (MAB) 60.3 reacts with the beta chain (CD18) of lymphocyte function associated antigen (LFA-1), encoded by a gene on chromosome 21. We have used 60.3 to measure the expression of CD18 on lymphoblastoid cell-lines derived from persons with Trisomy 21 (Down syndrome) by quantitative fluorescence flow cytometric analysis. This showed that CD18 expression is increased on Trisomy 21 compared with normal cells, whereas neither HLA-class I, nor transferrin receptor expression are significantly affected. Similar results were obtained with the CD18 MAB MHM 23, and with the CD11a MAB MHM 24 (LFA-1 alpha). These results suggest that the increase in CD18 expression by Trisomy 21 cells is due to gene dosage, and could influence the immune status of persons with Down syndrome.

Antibodies, Monoclonal↗
PubMed1987

Expression of human CD antigens, including CD1 and CD25, by human x mouse interlineage leukaemia hybrids.

The expression of human cell-membrane antigens by hybrid cell lines derived by fusing a human B-ALL and mouse BW 5147 T-lymphoma cells has been studied. Using monoclonal antibodies (mAb), the phenotypes of 19 of the 24 hybrids which grew 11-44 days post-fusion have been analysed by indirect membrane immunofluorescence (IF). These uncloned hybrid cells were assayed early after outgrowth, prior to extensive human chromosome and antigen loss. Nonetheless, cytogenetic analysis showed that all hybrids contained variable numbers of human chromosomes. Phenotypic analysis showed that the hybrids could be grouped as follows: a high frequency expressing CD25 (IL-2 receptor), human T200, HLA class I alpha and beta 2microglobulin, and reacting with the mAb H207 and 12E7; an intermediate frequency expressing CD1 and CD2; and a low frequency expressing CD3, CD4, CD5, CD7, CD8 and CD9. This pattern of antigen expression resembled the frequency of these cells in the human B-ALL parent line. Cell sorting was used to immunoselect hybrids expressing CD1 and CD2, but CD1 expression was unstable during subsequent culture.

Animals↗
PubMed1986

Lymphokine activated killing of fresh human leukaemias.

The relative susceptibility of 10 human leukaemias comprising acute phase leucocytes from 5 acute myeloid and 5 lymphoid neoplasms, and 2 immunoblastic lymphomas to killing by peripheral blood mononuclear cells (PBMC), before and after target cell treatment with phytohaemagglutinin (PHA), and by interleukin-2 (IL-2) activated peripheral blood lymphocytes (PBL) was investigated in short term 51Cr release assays using effector cells from 10 allogeneic donors. Optimal lectin-dependent cellular cytotoxicity (LDCC) was verified against K562 and L1210 cells and lymphokine-activated killing (LAK) against K562 and Daudi cells. Under these conditions, the majority of the leukaemias tested revealed only a finite sensitivity to any of the cytotoxic mechanisms, which was dependent on the donor origin of the effectors. The leukaemias were more consistently susceptible to LDCC than LAK and removal of adherent cells to enrich for the latter activity in effector populations, was ineffective. Lymphocytes from a patient in long term (greater than 5 yr) remission exhibited LAK against the autologous target E84, a natural killer (NK)-sensitive acute myelomonocytic leukaemia. These cells failed to cross-compete for lysis of K562 by LAK cells, suggesting the existence of different recognition structure(s) on the two targets.

Cell Line↗
PubMed1986

Concentration and molecular forms of active and inactive renin in human fetal kidney, amniotic fluid and adrenal gland: evidence for renin-angiotensin system hyperactivity in 2nd trimester of pregnancy.

In a study of 38 fetuses total kidney renin was significantly correlated with gestational age (r = 0.63). Although whole fetal kidney renin specific activity was found to decrease with gestational age (r = -0.65), the mean value of the specific activity was about 20 times greater than in normal adult cortex and double that in tissue from patients with renal artery stenosis, suggesting renin-angiotensin system hyperactivity. In approximately 40% of fetal kidneys examined, evidence for an inactive (trypsin-activatable) renin precursor was found. The molecular weight of this form was indistinguishable from active renin (45 000 daltons) by Sephadex chromatography. Amniotic fluid from nine cases (100%) contained angiotensin (ANG) 1, angiotensin converting enzyme (ACE), renin substrate, active and inactive renin (both 45 000 daltons). Five of the 38 (13%) fetal adrenal glands contained renin, but no evidence for trypsin-activatable forms. Aldosterone was present in low concentration in the earliest adrenals examined, and a positive correlation existed between total tissue aldosterone and gestational age (r = 0.73). These findings suggest that the fetal renin-angiotensin system has an important role to play in the maintenance of extracellular fluid volume and blood pressure in the developing fetus.

Adrenal Glands↗
PubMed1986

Active and inactive renin in anephric man: a comparison of molecular weight studies with normal human plasma and the effect of a specific monoclonal anti-renin antibody.

Measurements of active and inactive renin have been made in a group of six anephric patients and in 30 normal healthy volunteers. Plasma renin activity (PRA) was detected in all of the anephric patients but values were below the normal range. A trypsin-activatable totally inactive renin was present in the plasma of all six patients. In three patients, levels of inactive renin were greater than that found for the mean value of the control group. Gel filtration studies of anephric plasma revealed a degree of heterogeneity of molecular forms of active high molecular weight (HMW) renin. However, an active form of approximately 65,000 daltons was usually present. Inactive renin, partially purified from anephric plasma had an apparent molecular weight (MW) of 59,000 daltons. Affinity chromatography with H.77 Sepharose was used to purify active renin from anephric and normal plasma following treatment with trypsin. The increased PRA in plasma from both groups following trypsin was associated with a 56,000 daltons form indicating little, if any, change in MW upon activation. The active HMW forms and the activated inactive renin were all totally inhibited by a renin-specific monoclonal antibody raised against human kidney renin.

Adult↗
PubMed1985

Expression of HLA class I alpha chain determinants by human X mouse hybrid T cells is correlated with HLA-beta 2m but not with H-2.

The expression of HLA class I alpha chains by clones derived from a human X mouse T-cell line containing human chromosomes 6 and 15 was analysed by immunofluorescence. Evidence is presented showing that the expression of HLA class I alpha chains is associated with HLA-beta 2m. This is based on the phenotypic and quantitative fluorescence flow cytometric analysis of a series of cloned hybrids. In contrast, HLA and H-2 class I determinants show no evidence of such correlation. Results of cell-sorting indicate that the loss of HLA class I alpha chain expression is due to phenotypic modulation, in addition to gene segregation.

Animals↗
PubMed1984

Lack of correlation between lymphocyte activating determinants and HLA-DR on acute leukaemias.

The expression of allogenic lymphocyte-activating determinants (LAD) on 25 acute leukaemias has been compared with the expression of cell-surface antigens identified by HLA-DR allo- and xeno-antisera. The close correlation between LAD and DR known to occur on normal lymphocytes was not found in leukaemias. Twenty-two LAD+ leukaemias included 2 DR- cases, whilst 2 LAD- leukaemias were DR+. With the exception of 3 leukaemias all were strongly beta 2 microglobulin+. No correlation was found between the % DR+ cells and the level of lymphocyte stimulation. Separation of leukaemia cells on Ficoll gradients into fractions containing different proportions of DR+ cells did not correlate with LAD expression. Furthermore, antisera to DR antigens only partially blocked leukaemic LAD. The results support the notion that LAD on acute leukaemias are not necessarily associated with or identical to HLA-DR antigens, and that the lymphocyte activating capacity of HLA-DR may be modulated.

Acute Disease↗
PubMed1984

Optimum cell numbers for mixed lymphocyte responses in hanging-drop microcultures.

The conditions required for optimum mixed lymphocyte culture (MLC) responses in hanging-drop (HD) microcultures in Terasaki trays have been investigated. Compared with conventional (200 microliter) MLC, HD-MLC required 5-10 times fewer cells, and 10% of the amount of culture medium and 3H-thymidine label. Peak uptake of label in HD-MLC was mutually responder-stimulator concentration dependent. Differences in response to related and unrelated lymphocytes indicate that HLA-D determinants are detected in HD-MLC.

Cell Count↗
PubMed1984

Characterization of a human X mouse T cell hybridoma and identification of a clone secreting and binding interleukin-2.

Human lymphocytes stimulated with phytohaemagglutinin (PHA) were fused with an HGPRT- murine lymphoma, BW5147, and a hybridoma BwFc93-1 was isolated and cloned in agarose. This human X mouse hybrid and nine clones derived from it were characterized by chromosome analysis, phenotypic and functional assays. Karyotyping and isoenzyme studies showed the presence of five human chromosomes in BwFc93-1 with preferential retention of three chromosomes--6, X and 15--in the clones. Membrane immunofluorescence analysis revealed that all the clones expressed human and mouse class 1 MHC antigens and the mouse T cell antigens Thy-1 and T200, but were devoid of human OKT3, OKT8 and mouse Lyt-2. Human OKT4 and OKM1 phenotypes were transiently expressed by one clone and mouse Lyt 1 by two other clones. Several T4-, Lyt-1- clones produced and bound human interleukin-2 (IL-2) indicating a lack of correlation between human T cell phenotype and function in those hybrids. There was also evidence of dichotomy in the secretion of IL-2 and expression of the IL-2 receptor since clones were identified which either bound or secreted IL-2. One clone expressing IL-2 receptors could be induced to produce human IL-2 by simultaneously stimulating with PHA and phorbol myristate acetate (PMA).

Animals↗
PubMed1983

An HLA-DR negative acute leukaemia which stimulates MLC and CMC responses.

We describe an acute myelomonocytic leukaemia (E72) devoid of cell-surface HLA-DR antigens, but capable of inducing cellular responses. Leukaemia E72 induced proliferation of normal lymphocytes in primary mixed lymphocyte culture (MLC), which was only weakly inhibited by anti-DR sera. Depletion of a small percentage (congruent to 4%) of DR+ cells on a cell-sorter failed to abrogate the capacity of E72 to stimulate MLC and cell-mediated cytotoxicity (CMC) responses. We found that normal lymphocytes primed with E72 responded in secondary MLC to lymphocytes and leukaemias, suggesting that the lymphocyte-activating determinant (LAD) on E72 is not leukaemia-specific. In addition, E72 induced CMC responses to both leukaemias and lymphocytes. We suggest that E72 may express a novel HLA or non-HLA LAD.

Aged↗
PubMed1983

The role of allogeneic cells in the stimulation of cell-mediated cytotoxicity to leukaemia cells. A family study.

Allogeneic lymphocytes can stimulate cell-mediated cytotoxicity (CMC) in lymphocytes from leukaemia patients against autologous leukaemia target cells. We have compared the capacity of different allogeneic lymphoid cells to stimulate CMC to fresh (i.e., patient) and cultured (MOLT 4, K562) leukaemic target cells in lymphocytes from an acute leukaemic patient and his HLA-identical siblings. Allogeneic lymphoid cells, and particularly a lymphoblastoid cell line, were effective in stimulating CMC to leukaemia targets. In some instances, however, leukaemia cells derived from the patient, mixed with allogeneic lymphoid cells stimulated synergistic CMC to the patient's leukaemia. We also found that the patient's leukaemia cells alone were able to stimulate CMC in HLA-identical sib lymphocytes to fresh and cultured leukaemia targets. Extra specificities on fresh leukaemia cells were revealed when these cells induced unpredicted CMC on normal lymphocyte targets when added to mixed lymphocyte cultures (MLC) between related and unrelated lymphocytes. Cytotoxic lymphocytes generated in MLC against the patient's HLA antigens were absorbed by monolayers of lymphocytes and leukaemia cells of the same HLA type as the patient, leaving residual CMC to fresh (patient) and cultured (K562) leukaemia target cells. In addition, CMC to the patient's leukaemia cells, stimulated in lymphocytes from the patient's HLA-identical sib by allogeneic cells, was absorbed by a monolayer of these allogeneic cells. This suggests cross reactivity between determinants on the leukaemia and allogeneic lymphocytes. The results of this study are consistent with expression of 'leukaemia antigen', which are not restricted to leukaemia cells but may also be expressed on lymphocytes.

Aged↗
PubMed1983

The subcellular distribution and storage form of renin in human kidney cortex.

An assay with the cation exchange resin Dowex 50 WX2 was developed and validated for the measurement of renin activity in subcellular fractions of kidney cortex. After differential centrifugation, renin was found predominantly in the soluble (SOL) fraction (70%) and to a lesser extent in the heavy mitochondrial (HM) extract (17%). Neither acid pH nor trypsin treatment increased renin activity in these fractions. Discontinuous and continuous sucrose concentration gradients were used to partially resolve renin-containing organelles in the granular moiety from marker enzymes for mitochondria, lysosomes, plasma membranes and peroxisomes. The molecular weight (MW) of renin in both the SOL and HM was approximately 45 000. No acid or trypsin-activatable forms of renin were found after gel filtration of these extracts. When renal cortical tissue was extracted in the presence of the proteolytic enzyme inhibitors N-ethylmaleimide (NEM), ethylenediaminetetraacetic acid (EDTA), aprotinin, phenylmethylsulfonyl fluoride (PMSF), benzamidine and pepstatin, renin activity was not increased by added trypsin. After gel filtration of the homogenates, the MW of renin activity was 45 000. Protease inhibitors did not appear to preserve high molecular weight (HMW) forms and no trypsin-activatable renin was found. These results suggest that in man renal renin is stored within mechanically fragile granules and that the major storage form is of low molecular weight (LMW).

Centrifugation, Density Gradient↗
PubMed1982

Susceptibility of human leukaemias to cell-mediated cytotoxicity by interferon-treated allogeneic lymphocytes.

Twenty-two human leukaemias, comprising acute phase leucocytes from 13 acute myeloid and nine lymphoid leukaemias, were tested for susceptibility to spontaneous cell-mediated cytotoxicity (CMC) by untreated lymphocytes and lymphocytes treated for 18 h with 250 IU lymphoblastoid (Namalva) interferon (IFN-alpha). IFN-amplified killing (IAK) by lymphocytes from 24 normal lymphocyte donors was checked on the K562 erythroleukaemia cell line, for comparison with IAK on fresh leukaemias. Nine leukaemias were tested with lymphocytes from three donors, nine with lymphocytes from six donors, three with lymphocytes from nine donors, and one with lymphocytes from 11 donors. Some degree of susceptibility to IAK was found in five acute myeloid and five lymphoid leukaemias, which was markedly dependent upon the source of the effector lymphocytes and did not correlate with the degree of IAK on K562. The 12 other leukaemias were virtually resistant to IAK. The results emphasize the variability in the capacity of IFN-treated lymphocytes to lyse leukaemias that have not been adapted to tissue culture. The basis of effector recognition of cell line and fresh tumour targets is discussed.

Cell Line↗