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Biomedical subjects

E Kedar

Publications and source records attributed to E Kedar.

At least 73 records · Page 4Linked to original sources
PubMed1983

Murine interleukin-2 generates glycogen-rich and mucus-secreting NK cells.

Colonies of cells termed 'giant granular leucocytes' (GGL) displaying natural killer (NK) activity were generated in cell culture. The prominent feature of these cells was the formation of large cytoplasmic pool--the 'theca'--filled up with glycogen. This was demonstrated by the strong positive red staining of the theca with periodic acid Schiff reagent (PAS) which was abolished by prior treatment with amylase. Two different procedures were employed for obtaining colonies of NK-GGL. In the first, mice were injected either with killed Corynebacterium parvum or with killed Bordetella pertusis preparations and their mesenteric lymph-node cells were grown on syngeneic X-irradiated embryonic skin fibroblast monolayers. At the foci of GGL formation the fibroblasts were killed and the cleared areas thus formed were populated by adherent GGL. In the second procedure, supernates from rat or mouse spleen cultures stimulated with concanavalin A (Con A)--Interleukin-2 (IL-2)--were added to cultures of spleen and lymph-node cells prepared from either ordinary or from athymic nude mice. Richest GGL populations developed when rat IL-2 was added to cells of nude mice. Mouse IL-2 was less consistent. With nude mouse cells it stimulated, either mast cells or GGL, or both; rat IL-2 did not stimulate mast-cell differentiation in nude mouse cultures. In contrast, supernates from lymph-node cell cultures prepared from mice infected with Schistosoma mansoni. Mucosal mast cell-stimulating factor (MMSF) stimulated the formation of colonies of mast cells but not GGL. When MMSF was added as late as 23 days, colonies of young mast cells appeared and mast cells progressively increased in number. When rat IL-2 was added to such mature mast-cell cultures on the 30th day, colonies of cytolytic-GGL appeared. These observations indicate that precursors of mast cells and GGL persist in the cultures and preserve their potential to be stimulated by T-cell factors. GGL-NK cells developed on monolayers prepared from whole embryos released substance that displayed morphology and staining characteristic of mucus. Evidence gathered from in-vitro and in-vivo studies links the in-vitro GGL-NK cells to motile cells that inhabit the mucosal epithelium. Based on the observations, a hypothesis on the function of NK cytotoxicity is brought forward. It proposes the replacement of ordinary epithelial cells, which are killed during a proliferative and differentiative response of other cells at the onset of an infection course.

Amylases↗
PubMed1982

Natural cell-mediated cytotoxicity in vitro and inhibition of tumor growth in vivo by murine lymphoid cells cultured with T cell growth factor (TCGF).

Lymphoid cells obtained from the spleen, thymus, bone marrow, peripheral blood, and peritoneal exudate of normal mice (BALB/c, BALB/c nude, C57BL/6, C3H) and from spleens of mice bearing a transplantable lung carcinoma or primary mammary carcinoma were expanded in culture for 1-9 months, with an increase in cell number of 10(5)- to 10(6)-fold per month, in crude or lectin-depleted medium containing T cell growth factor (TCGF). All these cultured lymphoid cell (CLC) lines exhibited strong cytotoxic activity in vitro (assessed by 51Cr-release assays) toward a variety of freshly harvested and cultured syngeneic, allogeneic, and xenogeneic tumor target cells, both lymphoid and solid (including metastatic growths) in origin. Extensive killing was observed against tumor targets that were resistant to lysis by natural killer (NK) cells as well as to NK-sensitive tumor lines. Low levels of cytotoxic reactivity were also demonstrated against fresh and cultured normal lymphoid cells. The CLC had some characteristics of NK cells but also expressed some typical T cell markers. In local Winn-type neutralization assays, CLC delayed or completely inhibited the growth of lymphomas and carcinomas in syngeneic and allogeneic recipients. In mice with metastatic growth of a second-generation transplant of mammary carcinoma, CLC were shown to have some therapeutic effect when administered IV 1 day after cyclophosphamide. No significant beneficial action of IV administered CLC was observed in the absence of chemotherapy in mice implanted with a lung carcinoma. The possibilities of employing TCGF-propagated cytotoxic effector cells in adoptive immunotherapy of human malignancies are discussed.

Animals↗
PubMed1982

Expression of H-2b alloantigens in a variant of a Moloney virus-induced YAC (H-2a) lymphoma.

Splenocytes of A(H-2a), BALB/c(H-2d) and C57BL/6(H-2b) mice that were sensitized against several allogeneic normal lymphocytes and lymphoma cells in mixed lymphocyte cultures (MLC) and mixed lymphocyte-tumor cell cultures (MLTC) exhibited the expected cell-mediated cytotoxic responses against normal and tumor cells carrying the relevant alloantigens. In contrast, strong cytotoxic reactivity cross-reactive with C57BL/6 target cells was observed when a variant of YAC lymphoma (YAC-b) of strain A mice were employed either as sensitizers or as targets. Furthermore, this 'unpredicted' cross-reactivity was also obtained with syngeneic responder splenocytes sensitized to YAC-b cells. The possibility that the nonspecific cytotoxicity was caused by activation of natural killer (NK) cells in the culture was excluded by the finding that the cytotoxic capability of sensitized effector cells was greatly diminished by treatment with anti-Thy 1.2 serum and complement. Serologic analysis with anti-H-2 alloantisera revealed that the YAC-b tumor line, but not the parental YAC lymphoma, carried H-2b alloantigens. It is concluded that the 'unpredicted' cytotoxic responses here observed is a result of conventional antigen recognition and of specific sensitization to alien H-2b components expressed on the YAC-b subline.

Animals↗
PubMed1982

A rapid technique for isolation of viable tumor cells from solid tumors: use of the tumor cells for induction and measurement of cell-mediated cytotoxic responses.

A rapid and simple technique for the isolation of viable tumor cells from human and mouse solid neoplasms is described. It consists of a 5 to 10-min treatment with trypsin-collagenase-DNase mixture, followed by mechanical disaggregation of the tumor tissue and subsequently by a brief centrifugation on a discontinuous Percoll gradient. With the tumors employed, this procedure usually requires less than 1 hr and results in preparations comprising greater than 80% tumor cells with viability of 80-90%. Cell-mediated cytotoxic response was measured with: (a) unsensitized lymphocytes freshly obtained from tumor-bearing hosts; (b) lymphocytes propagated in culture with T cell growth factor; and (c) lymphocytes stimulated in cocultures with autologous or syngeneic tumor cells. The cytotoxic activity was assessed in a modified [51Cr]-release assay adapted for solid tumor cells, allowing a long incubation period (24 hr) and the use of a low number (200-1000) of highly labeled target cells (2-10 counts/min/cell).

Animals↗
PubMed1981

In vivo anti-tumor effects of local adoptive transfer of mouse and human cultured lymphoid cells.

Mouse and human lymphoid cells were cultivated in the presence of T-cell growth factor (TCGF) and evaluated for their in vivo anti-tumor effect in mice. Cultured spleen cells of normal BALB/c mice or of mice bearing the M109 tumor had a high level of cytotoxic activity in vitro against a variety of tumor target cells and had characteristics of natural killer cells. These cultured cells were evaluated for their in vivo cytotoxic activity by a mixture with [125I]dUrd-labelled M109 tumor cells (2 x 10(5)) at a 30:1 ratio and inoculation of the mixture into the footpads of BALB/c mice. The level of radioactivity remaining in the footpad was determined at various periods following inoculation of radiolabelled tumor cells. The presence of cultured cells in the inocula caused a marked decrease in the footpad radioactivity by 24 h. However, the slope of clearance of the radiolabel then became similar to that in the control mice. The cultured cells delayed, but did not prevent, tumor appearance, and did not influence the subsequent rate of growth of the tumors. The transient effects of the cultured cells contrasted with the more prolonged in vivo effects of alloimmune lymphocytes, and this may be due to their short survival period. Ninety-nine percent of [125I]dUrd-labelled cultured mouse lymphoid cells were eliminated within 48 h of i.f.p. inoculation. Cultured human lymphoid cells, initiated from the blood of normal donors, also had a high level of cytotoxic activity in vitro and were evaluated for their in vivo effects by intra-footpad inoculation into nude mice, together with radiolabelled human tumor cell lines, G-11 or HT-29. In vivo cytotoxic activity of the human cultured lymphoid cells correlated with their cytotoxic effect in vitro. These results indicate that cultured mouse an human effector cells have appreciable in vivo cytotoxic effects against tumor cell lines. However, the transient duration of these effects may limit their immunotherapeutic potential.

Animals↗
PubMed1980

In vitro generation of cytotoxic lymphocytes against radiation- and radiation leukemia virus-induced tumors. III. Suppression of anti-tumor immunity in vitro by lymphocytes of mice undergoing radiation leukemia virus-induced leukemogenesis.

Adult C57BL/6 mice exposed to fractionated irradiation or inoculated with the radiation leukemia virus (RadLV), develop high incidence (80-100%) of lymphatic leukemias within 3-6 mo. RadLV-induced lymphomas can elicit cytotoxic responses in vitro in lymphocytes of preimmunized syngeneic mice, a reaction that is dependent on the expression of membrane-associated viral antigenicity. As soon as 5 d after RadLV inoculation, and during the entire leukemogenic process, suppressor T cells are detectable in the spleen that are capable of specifically abrogating generation of syngeneic anti-tumor cytotoxic cells in vitro. Mice exposed to fractionated x irradiation do not develop suppressor cells and their splenocytes may be stimulated in vitro to generate cytotoxicity toward RadLV-induced leukemias. These findings suggest that although RadLV has been isolated from radiation-induced leukemias, x-ray- and RadLV-induced leukemogenesis do not seem to involve a common viral etiology, and that induction of suppressor cells during RadLV leukemogenesis may be essential for tumor progression.

Animals↗
PubMed1979

In vitro induction of cytotoxic effector cells against human neoplasms. I. Sensitization conditions and effect of cryopreservation on the induction and expression of cytotoxic responses to allogeneic leukemia cells.

Peripheral blood lymphocytes (PBL) from normal human donors were sensitized in vitro against allogeneic human acute myelocytic leukemia (AML) cells by means of an unidirectional mixed lymphocyte-tumor cell culture (MLTC) technique. The cytotoxic responsiveness of the sensitized lymphocytes, as determined in vitro by the 51Cr-release assay, varied among individual lymphocyte donors and was greatly dependent on the sensitization culture conditions. Induction of cytotoxic effector cells was augmented appreciably by adding to the cultures minute amounts of the immunopotentiating agent MER-BCG. Responding lymphocytes and stimulating leukemia cells cryopreserved for several weeks in liquid nitrogen were as effective as fresh cells in generating effector lymphocytes; the cytotoxic capacity of already sensitized lymphocytes was fully retained by cryopreservation. The implications of these findings for possible clinical employment of in vitro sensitized lymphocytes in adoptive immunotherapy of cancer are discussed.

Adult↗
PubMed1978

In vitro induction of cell-mediated immunity to murine leukemia cells. III. Effect of methanol extraction residue fraction of BCG on the generation of cytotoxic lymphocytes against leukemia.

Effects of the methanol extraction residue (MER) fraction of tubercle bacilli (BCG) on the generation of cytotoxic lymphoid cells were studied in vitro with the use of unidirectional mixed lymphocyte-tumor cell cultures. These cultures consisted of splenocytes of lymph node cells from normal donor C57BL/6, BALB/c, and strain A mice and mitomycin C-inactivated leukemia cells of both syngeneic and allogeneic origin. Addition of small amounts of MER (0.2-5 microgram/ml) to the cultures potentiated appreciably the elicitation of cytotoxic reactivity (as measured by the 51Cr-release assay) of the sensitized cells, whereas higher quantities (10-40 microgram/ml) had a strong suppressive effect. MER also induced some cytotoxic capacity in normal murine and human lymphoid cells not exposed to specific tumor cell stimulation. The stimulatory and suppressive effects were noted only when MER was present during the initial 24-48 hours of the 6-day culture. With the nylon wool fractionation technique, it was apparent that MER affected primarily the nonadherent cell population. MER could also prevent the generation of nonspecific suppressor cells by splenocytes maintained for 3-6 days in tissue culture.

Animals↗
PubMed1978

In vivo and in vitro induction of cytotoxic lymphocytes by alloantigen-reactive lymphocytes fractionated on spleen cell monolayers.

The generation of cytotoxic T cells by normal and primed lymphocytes fractionated on spleen cell monolayers was examined by two methods. In the first method, sublethally irradiated recipients were inoculated with the fractionated cells, and 5 to 6 days later the spleens were tested for cytotoxicity against 51Cr tumor target cells syngeneic to the host. Significant reduction of cytotoxic activity was observed in one-half of the experiments. In the second method, the fractionated cells were cultured with mitomycin C-treated stimulated cells and tested 6 days later for cytotoxicity. A slight reduction of cytotoxic activity was observed. In both methods, the cytotoxic response generated by the fractionated alloantigen-primed lymphocytes was similar to the response obtained with unprimed cells.

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