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T Timonen

Publications and source records attributed to T Timonen.

At least 55 records · Page 3Linked to original sources
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↗
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↗
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↗
PubMed1979

Human natural killer cell activity is augmented by interferon via recruitment of 'pre-NK' cells.

Contact with various cell-line targets increases the natural killer (NK) activity of human lymphocytes. Supernatants of such 20 h co-cultures augment the NK activity of virgin lymphocyte populations, and the augmenting factor penetrates 0.2 micrometer Millipore filters. The supernatants also contain interferon, and partially purified human leucocyte interferon increases NK activity when added to 20 h assays with 51Cr-labelled K-562 target cells. Potent anti-interferon antiserum added to the co-cultures inhibits the target-cell-induced augmentation phenomenon. Both the target-cell contact and interferon-induced augmentation affect a population of human lymphocytes, from which the 'mature' NK cells have been removed by adsorption-elution using fetal fibroblasts as adsorbents. The activity of 'mature' NK cells is not enhanced, and we conclude that the augmentation is mediated by recruitment of 'pre-NK' cells.

Adsorption↗
PubMed1979

Human natural cell-mediated cytotoxicity against fetal fibroblasts. IV. Comparison of cytotoxic activity with antibody-dependent cell-mediated cytotoxicity.

The dependence of human natural killer (NK) cell activity on antibodies was investigated. Absorption of the culture medium with target cells, trypsinization of the effector cells followed by a brief recovery, and incubation of the effector cells in serum-free nutrient medium did not affect natural killer cell activity against fetal fibroblasts. No soluble mediator in the nutrient media of effector cell--fibroblast co-cultures could be demonstrated. It was therefore concluded that antibodies are not involved in the cytolytic activity of natural killer cells. However, competition data and the activity of isolated NK cells against antibody-coated target cells suggested overlapping between the effector cells mediating natural and antibody-dependent cell-mediated cytotoxicity.

Antibody-Dependent Cell Cytotoxicity↗