Irradiated Lymphoid Cells Research Articles

Model for the initiation of ionizing radiation-induced apoptosis in lymphoid cells by complex DNA double-strand breaks

Purpose : To present a model for the molecular events that lead to the induction of apoptosis in irradiated lymphoid cells based on the assumption that the process is triggered by complex DNA double-strand breaks (DSB). Outline of the model : •Cellular DNA repair mechanisms have difficulty rejoining complex DSB because of the nature of the end groups on such breaks. •Association between p53 and DNA topoisomerase I (topo I) can occur at complex DSB in open regions of the genome and the enzymic activity of such associations is not suppressed by polyADP-ribosylation. •Binding of p53 and topo I at a complex DSB results in the transient trapping of a DNA-topo I cleavage complex. •Transiently trapped DNA-topo I cleavage complexes at complex DSB are reversed following association with topo I bound elsewhere in the genome, thus initiating a misrejoining event. •Topo I-mediated DNA misrejoining creates a structure that activates p53. Initiation of rapid interphase apoptosis requires that the inducing signal from activated p53 exceeds a threshold level. •Initiation of rapid interphase apoptosis is regulated by poly(ADP-ribose) polymerase.

Effects in vitro of cadmium ions on some membrane and nuclear parameters of normal and irradiated thymic lymphoid cells.

Effects of cadmium chloride upon 3H-Con A binding, number of autologous rosette-forming cells (ARFC), cell viability and the degree of DNA supercoiling were studied in normal and irradiated thymic lymphoid cells, isolated from rats and incubated up to 6 h in vitro. Cd (10-100 microM) did not significantly alter the patterns of surface markers and viability of normal thymocytes, as measured by supravital staining or nuclear pyknotic criteria. The following effects of Cd were noted for irradiated thymic cells: 1) Cd ions (25 microM) caused elimination of radiation-induced increase of Con A binding; 2) the characteristic loss of ARFC receptors, like development of nuclear pyknosis, was prevented in the presence of CdCl2 (10-100 microM); 3) the postradiation relaxation of nuclear supercoiled DNA was distinctly less pronounced with Cd. Possible reasons for these effects of Cd are discussed. Irradiated lymphoid cells are proposed as a suitable experimental model for the studies of different toxic actions of Cd and other heavy metals.

Production of human T-lymphocyte clones. I. Monoclonal culture and functional cytotoxic maturation

Well-defined clones of human T-lymphocytes were produced amd monoclonal T-cell cultures were maintained for long periods of time. Single T-lymphocytes were isolated with the help of a micropipette from PBL cultures prior to any cellular stimulation (MLC), collected separately at the bottom of a 200 μl tissue culture microwell under the control of stereomicroscopic observation, and cultured with irradiated lymphoid cells in the presence of TCGF. After 12 days, 20–50% of the seeded wells exhibited clones of 3 × 10 4 − 10 5 T-lymphocytes, which were transferred to largeer tissue culture wells (2 ml, LINBRO) for long-term culture. Recloning of the growing cloned cells under the same conditions as the primary culture was carried out successfully. In the preliminary cytotoxic assays performed in 11 clones (a) a marked activity directed against lectin-coated targets was observed in many clones; (b) an important NK-like activity was exhibited by the clone 45B9 (65% of the tested cells lysed K562 cell targets); (c) 3 clones did not demonstrate cytotoxic activity against either PHA-coated L-1210 cells or K562 cell targets. These results could be explained hypothetically by the difference of functional maturation of T-cells within each clone.

Radiation Induced Loss of Anti-Ig Binding Ability of Lymphocytes

The effect of irradiation on the anti Ig binding ability of lymphocytes after irradiation was studied. Normal control and irradiated lymphoid cells were treated with rabbit anti mouse IgG fluorescein conjugated serum and the fluorescein positive cells compared. A reduction in the proportion of stained cells in the irradiated lymphocytes was found. It depends on the dose and on the incubation time at 37 degrees C after irradiation. The maximum effect was detected after 10 minutes of incubation, longer incubation is associated with a partial recovery of the stainability of the IgG receptors.

Stimulation of autochthonous lymphocytes by cells from normal and leukaemic lines.

THE mixed lymphocyte reaction (MLR) can possibly be regarded as an in vitro form of an in vivo phenomenon reflecting the recognition of “non-self” tumour specific or neo-antigens on the surface of lymphoid cells. A reaction similar to the normal MLR but of greater magnitude occurs when irradiated lymphoid cells from lymphoblastoid cell lines (LCL) are added to freshly isolated peripheral lymphocytes from allogeneic individuals1,2. The intense stimulation which occurred in every case when irradiated cells from various LCL were added to lymphocytes from a large number of individuals3 suggested the presence of extra surface determinants on the cells, which are not present on normal freshly isolated cells. We have investigated whether freshly isolated lymphoid cells could detect and respond to extra antigenic determinants on the surface of cell lines derived more than 3 months earlier from their own lymphoid cells.

DNA-synthesis in irradiated lymphoid cells: effects on temperature on the dose-response curve.

SummaryThe effects of x-rays on DNA-synthesis in suspensions of hamster spleen cells was studied. The nature of the dose–response curve was found to be dependent on two factors: the temperature at which the cells were irradiated and the temperature at which they were incubated with tritiated thymidine. Irradiation at 37°c and incubation at 37°c results in a monophasic semilogarithmic dose–response curve with a D37 per cent of 7 krads. Irradiation at 7°c with incubation at 37°c results in a biphasic dose–response relationship with the initial steep part of the curve having a D37 per cent of 4 krads and the shallow part a D37 per cent of 28 krads. 20°c irradiation followed by incubation at 37°c results in a biphasic curve with a steep portion having a D37 per cent of 4 krads and a shallow portion with a D37 per cent of 28 krads. Lowering the irradiation temperature to 7°c and incubating the irradiated cells at 17°c results in a monpohasic response with a D37 per cent of about 20 krads, whereas irradiation a...