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Biomedical subjects

T Timonen

Publications and source records attributed to T Timonen.

At least 91 records · Page 5Linked to original sources
PubMed1982

Positive self regulation of cytotoxicity in human natural killer cells by production of interferon upon exposure to influenza and herpes viruses.

Augmentation of natural killer (NK) activity by influenza A/PC and HSV-1 viruses appears to be caused by the induction of interferon (IFN) within the NK cell population itself. These viruses induced high levels of IFN production by human large granular lymphocytes (LGL) that could be readily isolated from peripheral blood by Percoll density gradients. These LGL, which have been previously shown to account for and to be highly associated with endogenous NK activity, became augmented in their lytic function during the 18-h period that IFN was induced. Non-LGL helper cells did not appear to be required in the NK-IFN system (either T cells, B cells, or monocytes). Removal of these latter cell types by treatment with OKT3 plus complement, anti-IgM plus complement, or preincubation with silica or carrageenan had no effect on the ability of LGL to respond to the viruses. Production of IFN was also detected, albeit at lower levels, from monocytes cultured for 18 h with viruses, but no cytotoxic activity was induced. On the other hand, T cells, even in the presence of monocytes, showed neither property, and longer cultures, with virus up to 4 d, still did not alter the pattern. The IFN produced by both LGL and monocytes were predominantly IFN-alpha, as assessed by neutralization assays with antisera to IFN-alpha, -beta, and -gamma. In an individual with detectable serum antibodies to influenza A/PC, however, the IFN induced in LGL appeared to be gamma, presumably because of specific recognition of the virus. These data suggest an efficient positive self-regulatory mechanism in NK cells that may be readily switched on by viruses.

Antibodies, Monoclonal↗
PubMed1982

The Finnish leukaemia group: levamisole in maintenance therapy of acute myeloid leukemia in adults.

The Finnish Leukaemia Group has carried out a randomized, multicenter trial to study the effect of levamisole on the remission maintained with 6-mercaptopurine and methotrexate in acute myeloid leukaemia in adults. Levamisole was given on 3 consecutive days every 2 weeks. Twenty-five patients received only chemotherapy, while 26 patients received levamisole as well. The patients receiving levamisole showed significantly better remission duration than those given only chemotherapy (P = 0.033, Mantel's summary chi 2-text). There are four long term survivors in the levamisole group versus none in the chemotherapy group. The remissions have lasted 48-75 months.

Adult↗
PubMed1982

Isolation of human and rat natural killer cells.

We describe a method for the purification of human and rat large granular lymphocytes (LGL), which are known to be the mediators of natural killer (NK) activity in these species. Plastic non-adherent and nylon wool passed blood mononuclear cells were separated into 7 fractions by discontinuous density gradient centrifugation on Percoll. Low density cells were highly enriched in LGL (up to 85% purity), whereas high density cells were typical small and medium sized lymphocytes devoid of NK activity. Human LGL could further be enriched by depleting high affinity sheep erythrocyte rosette-forming cells from the LGL-enriched Percoll fractions (resulting in up to greater than 90% purity). One critical variable in the separation technique was osmolarity, since the separation did not work optimally, if 290 mOsmoles/kg H2O in the Percoll solution was exceeded.

Animals↗
PubMed1982

The spin-lattice relaxation time in the blood of healthy subjects and patients with malignant blood disease.

To establish which constituents of blood influence the NMR relaxation time T1 of water protons in malignant blood diseases, 55 blood samples were studied (20 from healthy donors and 35 from patients with leukaemia, myelofibrosis and multiple myeloma). Relaxation time measurements were performed at 19.8 MHz resonance frequency and at a temperature of 33 +/- 1 degree C. There is a significant elevation of T1 over the normal level in whole blood, packed cells, and plasma of patients with blood disease. The relaxation rate R1 (= 1/T1) depends very strongly on the ratio of dry solids to water, which is in accordance with the three-state fast-exchange relaxation model.

Blood Physiological Phenomena↗
PubMed1981

Characteristics of human large granular lymphocytes and relationship to natural killer and K cells.

Recent evidence, has demonstrated an association between a subpopulation of peripheral blood mononuclear cells, morphologically identified as large granular lymphocytes (LGL), and natural killer (NK) activity. We have now evaluated more directly the role of LGL in both NK activity and antibody- dependent cellular cytotoxicity (ADCC), by using highly enriched populations of LGL, obtained by centrifugation of peripheral blood mononuclear cells on Percoll discontinuous density gradients. Both spontaneous and interferon- augmented NK and ADCC activities were exclusively associated with the LGL- enriched, low density fractions. The majority of LGL formed conjugates with NK-susceptible and antibody-coated target cells. Approximately 20 percent of small conventional lymphocytes also formed conjugates with the target cells for NK, but this was not associated with cytotoxic activity. Virtually all LGL were found to have receptors for the Fc portion of IgG (FcgammaR). The frequency of LGL among blood leukocytes was 2-6 percent. LGL could be enriched to an average purity of 95 percent by combining discontinuous density gradient centrifugation with subsequent adsorptions of the low density fractions on monolayers of immobilized immune complexes. About 50 percent of LGL were found to be FcgammaR-bearing T cells (T(G)), forming low affinity rosettes with sheep erythrocytes at 4 degrees C. Only 10-20 percent of LGL formed high affinity rosettes with sheep erythrocytes at 29 degrees C. LGL could be enriched to a purity of more than 90 percent by depleting high affinity rosette-forming cells from low density Percoll fractions. LGL were only a subpopulation of T(G) cells, because some lymphocytes with conventional morphology also adhered to the immobilized immune complex monolayers and formed high affinity rosettes with sheep erythrocytes. Separation of these cells from LGL by discontinuous density gradient centrifugation indicated that they are not cytotoxic, suggesting a morphological and functional subdivision of T(G) cells. The verification in this study that virtually all human NK and K cells have a characteristic morphology adds a useful parameter to the monitoring of human lymphocytes, and the ability to purify these cells by simple physical procedures should be invaluable in their further characterization.

Adsorption↗
PubMed1981

Augmentation of human natural killer cell activity by interferon: conditions required for boosting and characteristics of the effector cells.

Human effector cells of natural killer (NK) activity have been augmented by pretreatment with a partially purified preparation of interferon (IFN-beta). Using the 4-hr 51Cr release assay to measure cytotoxicity, the boosted effector cells, as well as the spontaneous NK cells, were nonphagocytic cells with receptors for the Fc portion of IgG. Augmentation of cytolytic activity occurred: (1) in medium with either fetal calf serum and human serum; (2) in the presence of absence of monocytes; (3) in both sheep RBC rosette-forming and non-rosette-forming populations; and (4) when only the effector cells were pretreated with interferon. This last observation led to the finding that less than or equal to 5 min of contact at 37 degrees C, 22 degrees C, or 4 degrees C with interferon was necessary for augmentation of cytotoxicity. Augmentation kinetics demonstrated significant boosting of NK activity in peripheral blood leukocytes and highly NK-enriched Percoll fractions after 1 hr of contact with IFN-beta or pure IFN-alpha-Collectively, these results indicate that NK boosting with interferon: (1) occurs after a rapid temperature-independent binding to the effector cells; and (2) has a rapid effect on the cytolytic process.

Blood↗
PubMed1981

Human large granular lymphocytes: spontaneous and interferon-boosted NK activity against adherent and nonadherent tumor cell lines.

Human natural killer (NK) cells against K-562 tumor cells have been morphologically identified as large granular lymphocytes (LGL). We have investigated whether LGL are also responsible for NK activity against a variety of adherent and nonadherent tumor cell lines. LGL-enriched fractions, obtained by centrifugation of nonadherent mononuclear cells on discontinuous density gradients of Percoll, contained high levels of spontaneous and interferon- (IFN) boosted NK activity against each of the target cells tested. In contrast, the LGL-depleted functions, which contain most of the typical small lymphocytes, were devoid of NK activity and did not develop appreciable activity after treatment with IFN. The ability of the different fractions to exert NK activity correlated with their capacity to form conjugates with nonadherent tumor cells. Reconstitution of the different fractions with macrophages did not increase the NK activity of already cytotoxic fractions and did not induce appreciable activity in the LGL-depleted fractions. On the other hand, mixtures of highly cytotoxic and nonreactive cell fractions did not reveal the presence of suppressor cells for NK in the nonreactive fractions. Taken together, our data demonstrate that both spontaneous and IFN-boosted NK activity is confined to the LGL-enriched fractions and suggest that LGL are the main effector cells exerting NK cytotoxicity against a variety of adherent as well as nonadherent tumor cell lines.

Cell Adhesion↗
PubMed1981

Determination of surface antigens on highly purified human NK cells by flow cytometry with monoclonal antibodies.

We examined highly purified populations of NK cells, T cells, monocytes, and PMN with a variety of monoclonal reagents presumed specific for T cells and monocytes. The enriched NK cells showed a pattern of reactivity that was distinct from that of the other 3 populations, sharing antigens with T cells but also sharing antigens with monocytes and/or PMN. A portion of the enriched NK cells expressed OKT8, OKT10, and Lyt-3 antigens that were reported previously as T cell-associated antigens, but no reactivity was seen with other T cell-associated antigens (OKT3, OKT4, OKT6, and OKT11). In addition a portion of the enriched NK cells were positive for OKM1, asialo-GM1, and Ia antigens, which are undetectable on typical T cells but are present on PMN and/or monocytes. By depletion of antigen-positive cells on antibody monolayers, it was found that the activity of the enriched NK population was associated mainly with cells reactive with OKT10, OKM1, and Lyt-3. Although considerable evidence exists to support the T lineage of NK cells, the sharing of some antigens by NK cells and monocytes has suggested a possible relationship of NK cells to cells of the monocyte lineage. A possibility certainly exists that NK cells are not in either T cell or monocyte lineages and may represent a separate lineage of lymphoid cells.

Antibodies, Monoclonal↗
PubMed1981

Natural killer (NK) cell activity in the rat. I. Isolation and characterization of the effector cells.

This study has demonstrated the presence of large granular lymphocytes (LGL) in the rat and implicated a central role for these cells in mediating natural killer (NK) cell activity in this species. The LGL frequency from various organs was shown to be: peripheral blood = lung greater than spleen greater than peritoneal exudate greater than lymph node. Little or no LGL were found in the thymus or bone marrow. This pattern was similar to the distribution of NK activity, except for the lungs, which had no detectable activity. These studies have also shown that discontinuous Percoll density gradients can be used to highly enrich or deplete LGL from both spleen and peripheral blood. Enriched LGL populations were shown to bind selectively to NK-susceptible target cells and to demonstrate very high NK cell cytolysis. Since human NK activity has also been found to be clearly associated with LGL, the present findings indicate that rats may provide a very useful animal model for detailed studies of the ontogeny, regulation, and in vivo relevance of NK cells.

Animals↗
PubMed1981

Defective neutrophil migration in monosomy-7.

The migration in vitro of neutrophils from six patients with monosomy-7 or partial deletion of the long arm of chromosome 7 was studied by two methods: the Millipore filter assay and the migration under agarose assay. Four of the patients had preleukemia, one had subacute myelomonocytic leukemia, and one polycythemia vera. In four patients, chemotaxis (migration towards a higher concentration of chemoattractant) and chemokinesis (stimulated migration without a gradient) were shown to be defective by both methods. In the remaining two patients, this defect could be demonstrated only by the Millipore filter assay or by the agarose assay. Under agarose, random locomotion (no chemoattractant present) of the patients' neutrophils was less than that of the control subjects in four patients, whereas no clear difference could be shown by the Millipore filter method. This study demonstrates that the previously described defect of neutrophil migration in monosomy-7 involves not only chemotaxis but all stimulated migration and, at least in some patients, random locomotion as well. Defective migration in two patients with an apparently terminal deletion of the long arm of one chromosome 7 indicates that the distal half of 7q carries genetic material important for neutrophil locomotion.

Adolescent↗
PubMed1980

Isolation of human NK cells by density gradient centrifugation.

Sedimentation characteristics of human NK cells in discontinuous Percoll density gradients were studied. NK activity against the leukaemic cell line K-562 peaked in a single low density fraction mainly consisting of large granular lymphocytes previously shown to be the principal NK cells in human peripheral blood. Percoll density gradient centrifugation provides a useful tool for analysis of human NK cells and their relationship to other blood mononuclear cells.

Cell Fractionation↗
PubMed1980

Induction of autologous reactivity of human NK cells.

'Mature' human natural killer cell activity could be enriched by adsorption-elution with fetal fibroblast as adsorbents against normal allogeneic skin fibroblasts, but not against autologous targets. However, when the natural killer activity was augmented by contact with tumour cells (HeLa), autologous and allogeneic skin fibroblast targets were killed without preference. Adsorption-elution with augmenting target cells as adsorbents resulted in an efficient enrichment of NK activity showing non-discriminate cytotoxicity. Morphologically, this was associated with an enrichment of large granular lymphocytes previously shown to be responsible for human NK activity. We conclude that the NK activity of human 'mature' NK cells shows a relative autologous exemption, whereas 'pre-NK' cells augmented to full activity in vitro are non-discriminative.

Adsorption↗
PubMed1980

Effect of leucocyte interferon on natural killer cells in healthy volunteers.

The effect of partially purified human leucocyte interferon on natural killer activity (NK activity) of peripheral blood in six healthy volunteers was tested in this study. After 4 h of intradermal injection of interferon, a rapid transient decline in NK activity and in the number of NK cells (large granular lymphocytes) in peripheral blood was observed. The decline was most distinct at 20 h and recovered at 72 h. Since no clear activation of Nk cells in peripheral blood was detected, the results suggest an extravasation of NK cells as a result of interferon injection. NK cells did not accumulate at the injection site on the skin, because the suction blister fluids over the injection sites did not contain increased numbers of NK cells.

Adult↗