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E Kedar

Publications and source records attributed to E Kedar.

At least 91 records · Page 5Linked to original sources
PubMed1977

In vitro induction of cell-mediated immunity to murine leukemia cells. II. cytotoxic activity in vitro and tumor-neutralizing capacity in vivo of anti-leukemia cytotoxic lymphocytes generated in macrocultures.

The main findings of the present study are: (a) highly reactive cytotoxic lymphocytes (CTL) against syngeneic and allogeneic murine leukemia cells were generated in vitro in macro 'one-way' mixed leukocyte-tumor cultures (MLTC). Cultures set up in large tissue culture flasks contained up to 400 X 10(6) normal spleen cells (responder cells) and 20--40 X (10(6) mitomycin C-treated leukemia cells (stimulator cells). Successful sensitization in macrocultures was greatly dependent upon the responder cell density and the responder/stimulator cell ratio. Cytotoxic activity, as measured by the 51Cr-release assay, peaked on day 5--7. (b) Sensitized 'memory' lymphocytes produced in primary MLTC could be restimulated with the original tumor cells to give a more rapid and stronger secondary cytotoxic response. (c) lymphocytes sensitized to allogeneic leukemia cells reacted equally well with sensitizing leukemia cells and with the corresponding normal lymphoid target cells, whereas lymphocytes sensitized to syngeneic leukemia cells did not react with the homologous normal lymphocytes. (d) Cryopreserved normal splenocytes and leukemia cells were as efficient as fresh cells in generating allogeneic and syngeneic CTL. (e) Using a Winn-type tumor neutralization assay, it was shown that both allogeneic and syngeneic splenocytes sensitized in vitro to EL4 leukemia (of C57BL/6 mice) and to YAC leukemia (of A mice) were capable of preventing tumor growth in the syngeneic host, whereas cultured normal splenocytes frequently showed a tumor-enhancing effect. Long-term survivors, remaining after inoculation of leukemia cells and sensitized lymphocytes, also became resistant to a tumor challenge that was up to 10,000 greater than the minimum lethal dose.

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PubMed1976

In vitro induction of cell-mediated immunity to murine leukemia cells. I. Optimization of tissue culture conditions for the generation of cytotoxic lymphocytes.

Cytotoxic lymphocytes (CTL) to allogeneic and syngeneic murine leukemia cells were generated in vitro in "one way" mixed lymphocyte-tumor cell cultures carried out under a variety of conditions. In an attempt to define the optimal culture conditions for sensitization, the following parameters were analyzed: culture vessel, culture volume, responder: stimulator (R:S) cell ratio, lymphoid cell density, source of lymphoid cells, duration of culture, fetal calf serum (FCS) concentration, 2-mercaptoethanol (2-ME) concentration, concentration of amino acids, and buffering system. Of the many variables examined, of particular importance were the R:S cell ratio, the cell density, the FCS concentration, the presence of 2-ME, and the time of harvesting. These factors exerted various effects, both quantitatively and qualitatively, on the magnitude and kinetics of the responses induced in microcultures (5 X 10(6) lymphocytes) and macrocultures (25 X 10(6) lymphocytes). Moreover, optimal sensitization in syngeneic cultures required different conditions than those for allogeneic cultures. Cytotoxic activity was assessed in vitro by a quantitative 51Cr-release assay. The sensitized lymphocytes demonstrated the characteristics ofT lymphocytes and reacted specifically with the sensitizing leukemia cells.

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PubMed1976

Immunogenicity of tumor cells modified by trinitrobenzene suflonic acid (TNBS).

The ability of trinitrophenylated tumor cells to stimulate syngeneic antitumor response has been tested in 3 different tumor-host systems: A. Trinitrophenylated and inactivated Moloney induced YAC tumor cells (YAC-TNP) were able to induce the production of cytotoxic antibodies in low responding A/J mice, while inactivated YAC tumor cells (YAC-In) failed to induce such a response. Furthermore, A mice which were injected with YAC-TNP rejected 103 viable YAC tumor cells at a higher frequency than those injected with YAC-In. B. Trinitrophenylated and inactivated Gross virus induced G-35 tumor cells or Monoloney induced LSTRA cells (both syngeneic in BALB/c mice) were as immunogenic as nonmodified inactivated tumor cells. About 50% of the immunized mice survived indefinitely after injection of 103 viable tumors. Fruthermore, spleen cells from mice primed with either modified or nonomodified G-35 cells responded in vitro to G-35 in a mixed leukocyte tumor interaction and generated specific cell-mediated cytotoxic activity to 51Cr-G-35 syngeneic tumors. However, the donors of the primed cells did not produce detectable cytotoxic antibodies to G-35. C. In vitro sensitization of C57B1 spleen cells by trinitrophenylated Mitomycin C treated syngeneic EL-4 generated a stronger cytotoxic response to EL-4 cells than obtained by sensitization with Mitomycin C treated EL-4 cells alone, The superiority of the sensitizing capacity of trinitrophenylated EL-4 was readily demonstrated in conditions which were suboptimal for nonmodified Mitomycin C treated tumor. Both theoretical and practical implications of these results are discussed.

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PubMed1975

Studies on the induction and expression of T cell-mediated immunity. IV. Non-overlapping populations of alloimmune cytotoxic lymphocytes with specificity for tumor-associated antigens and transplantation antigens.

Two non-overlapping populations of alloimmune cytotoxic T cells with specificity for tumor-associated antigens (TAA) and for histocompatibility antigens (H-2) were characterized by two independent methods. The heterogeneity of cytotoxic cells was demonstrated in spleen cells derived from BALB/c (H-2d) mice sensitized to EL-4 (H-2b) tumor and from C57BL/6 (H-2b) mice sensitized to G-35 (H-2d) tumor cells. Adsorption of immune lymphocytes on monolayers prepared with cells bearing the sensitizing H-2 antigens abrogated the in vitro cell-mediated cytotoxicity (CMC) directed against 51Cr-labeled normal target cells (spleen cells or ConA-activated spleen blasts), whereas significant cytolytic activity to the corresponding 51Cr-tumor cells was still retained. Likewise, in competitive inhibition assays, CMC to 51 Cr-tumor target cells was only partially inhibited by unlabeled normal cells, whereas CMC to 51Cr-normal target cells was completely abrogated. These results suggested that alloimmune cytotoxic lymphocytes are heterogeneous and can be subdivided into two independent populations of restricted specificity. Several experiments suggested that the effector cell population directed against TAA can no longer elicit a graft-vs-host (GVH) reaction in vivo. This was demonstrated by adoptive transfer into lethally-irradiated allogeneic recipients of cytotoxic or primed spleen cells fractionated on host target cell monolayers. Furthermore, these results demonstrated that both effector cells and memory cells possess high affinity binding receptors to corresponding H-2 antigens. The potential use of fractionated immune lymphocytes sensitized to tumor allografts in adoptive immunotherapy is discussed.

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