production of a cell line which when co - cultured with lymphocytes while avoiding allogenic stimulation leads to induction of lymphocytes to form tumoricidal t cells the production of an activator cell line according to the present invention is carried out by immortalization of lymphocytes according to the method described in ep - b 0 093 436 . for this human peripheral blood lymphocytes are firstly isolated by ficoll gradient centrifugation . cytoplasts from the mouse myeloma cell line p3x63 ag8 . 653 ( atcc crl1580 ) are produced by treatment with cytochalasin b as described in ep - b 0 093 436 . 1 × 10 7 of the human peripheral blood lymphocytes are mixed each time with 1 × 10 7 cytoplasts of the myeloma cell line ag8 . 653 and sedimented by centrifugation . the supernatant liquid is carefully removed . 0 . 8 ml 50 % polyethylene glycol 4000 solution is added at a slow constant rate over a period of 1 min while shaking gently and continuously . subsequently 5 ml dulbecco &# 39 ; s minimal essential medium ( dmem ) is added at room temperature over a time period of 5 min . after addition of a further 20 ml dmem , the cells are sedimented , resuspended in 5 ml fresh dmem complete medium and distributed in the wells of a cell culture plate coated with murine macrophages from the abdominal cavity as feeder cells . the individual cultures are then fed with dmem complete medium at intervals of two to three days . finally the clone is selected which can activate lymphocytes to form t lymphocytes . for this peripheral blood lymphocytes are firstly incubated with l - leucyl - l - leucine methyl ester as described in example 2 in order to eliminate cells which can be activated by allogenic stimulation to form tumoricidal t cells . the lymphocyte population obtained in this way is then co - cultured with the immortalized lymphocyte cell line to be tested under conditions which enable direct cell — cell contact . those immortalized lymphocyte cell lines which are lysed during such a co - culture by the tumoricidal t lymphocytes that are activated by them are examined further . for this these selected cell lines are cultured together with the tumoricidal t lymphocytes that are activated by them as well as with various tumour cell lines . finally , those immortalized activating lymphocyte cell lines are selected which during this process produce t lymphocytes with a tumoricidal effect on various tumour cell lines . this tumoricidal action is detected by the fact that the tumour cell lines which are morphologically distinguishable from the tumoricidal t lymphocytes as well as from the activating lymphocyte cell lines disappear from the culture during this co - culture or at least decrease in numbers compared to an untreated control culture . the cell line hb 654 was obtained in this way . permanent human b lymphocyte lines which had been immortalized by infection with the epstein - barr virus were examined for activator properties using the same procedure . twenty different ebv - positive b lines cloned by single cell culture are tested in a co - culture with blood lymphocytes which are pre - treated with leucyl - leucine methyl ester . the seeding density of the blood lymphocytes is 2 × 10 6 per ml culture medium ( iscove mod . dmem + 15 % fcs ; bm ). 50 -, 100 - and 200 - fold fewer cells of each of the b lines are added to the blood lymphocytes in separate preparations and incubated at 37 ° c . in a 5 % co 2 atmosphere . the cell line hb 617 was obtained in this manner which also has an action according to the invention . production of tumoricidal t lymphocytes by co - culture with the human b cell line hb 654 the mononuclear cells are isolated from human peripheral blood in the usual way by ficoll ® gradient centrifugation . in order to eliminate monocytes , macrophages , natural killer cells and mhc - restricted cytotoxic t cells , in particular those directed against allogenic mhc of the activating cell line hb 654 , and their precursors , the mononuclear cells obtained are incubated for 15 min at room temperature in pbs containing 250 μmol / l l - leucyl - l - leucine methyl ester according to thiele and lipsky ( the journal of immunology , vol . 136 , no . 3 ( 1986 ), p . 1038 - 1048 ). subsequently the cells are taken up in iscove &# 39 ; s modified dulbecco &# 39 ; s medium with 15 % fcs and , after adding a deficit ( ca . 1 : 10 ) of hb 654 cells , they are incubated for 6 to 8 days at 37 ° c . until tumoricidal t lymphocytes can be detected on the basis of their eliminating activity on the activator cell line . the tumoricidal t lymphocytes obtained according to example 2 each from 20 different donors are added to cultures of human tumour lines ( see tables i and ii ). the tumoricidal effect on these tumour cells is monitored under a microscope . the growth of these various tumour cell lines is inhibited or they are killed by the tumoricidal t lymphocytes according to the present invention . 5 ) ca . 2 colonies per 5 × 10 4 thp - 1 cells 6 ) ca . 10 colonies per 5 × 10 4 hl - 60 cells production of tumoricidal t lymphocytes ( killer t cells ) by means of cell - free membrane vesicles which are produced from hb 654 cells by treatment with cytochalasin b hb 654 cells are also induced to tie off membrane vesicles (“ blebs ”) using the method described by maul , g . d . ( in : techniques in somatic cell genetics , ed . j . w . shay ; plenum press , new york , 1982 ) by incubation with cytochalasin b ( cb , aldrich biochemicals ) which can be separated by allowing shearing forces to act on the cells ( without cell destruction ). hb 654 cells from cultures in a logarithmic growth phase are washed twice in serum - free culture medium ( rpmi 1640 , bm ), suspended in this medium at a density of ca . 2 × 10 7 cells / ml and heated to 37 ° c . cb ( stock solution : 5 mg / ml dmso ) is added ( final concentration : 25 μg / ml ). the suspension is incubated for one minute at 37 ° c . and then rotated for one minute on a vortex apparatus . the cells are suspended by low speed centrifugation . the supernatant containing vesicles is filtered through a 5 μm filter . on average a yield of 3 membrane vesicles is obtained from one hb 654 cell . mononuclear blood cells are isolated as described in example 2 by gradient centrifugation , treated with leucyl - leucine methyl ester and incubated at a density of ca . 2 × 10 6 cells / ml of a culture medium ( iscove mod . dmem plus 15 % fcs ) to which ca . 2 × 10 6 vesicles had been added per ml . the cells are supplied with fresh culture medium on day 7 and 10 which in turn contains 2 × 10 6 vesicles per ml . on days 3 , 7 , 10 and 13 the total number of vital blood cells ( pbl ) and the proportion of lymphoblasts in the culture are determined ( fig1 ). the determination showed that the number of living blood cells decreases at first and then increases on day 7 . on day 13 the number of vital cells is approximately 5 - fold the number of originally sown cells . the proportion of lymphoblasts increases from 0 % on day 1 of the culture to ca . 95 % on day 13 . the tumoricidal function towards the tumour lines jurkat , thp - 1 and hb654 of the lymphoblasts obtained according to b . is examined on day 14 after setting up the culture . the destruction of the tumour cells is measured using the “ cellular dna fragmentation elisa kit ” ( boehringer mannheim gmbh , ger , order no . 1585045 ) according to the manufacturer &# 39 ; s instructions . principle : tumour ( target ) cells are labelled metabolically by addition of 5 - bromo - 2 ′ deoxy - uridine ( brdu ) to the culture medium . proliferating cells incorporate brdu into the dna instead of thymidine . cytotoxic effects on these target cells can then be measured based on the release of brdu - labelled dna by means of an elisa ( enzyme - linked immunosorbent assay ) in which anti - dna antibodies bound to the wall and an anti - brdu antibody - peroxidase conjugate are used . after a 24 hour co - culture with the lymphoblasts according to b . at least 80 % of the tumour cell dna which can be maximally released is found in the culture supernatant in all three tumour lines at an effector / target ratio of 4 / 1 and of 100 % at an e / t ratio of 10 / 1 . production of killer t cells by subcellular vesicles which have been obtained in a physical manner by hypotonic shock a method modified according to jett et al ., ( jett et al ., j . biol . chem . 252 ( 1977 ), 2134 - 2142 ) was used as a further method of isolating subcellular fragments which are suitable for producing the claimed effect . the vesicles were obtained as follows : cells of the stimulator cell line hb 654 were washed in earls buffer ( containing 0 . 9 mm calcium chloride and 0 . 5 mm magnesium chloride in pbs buffer ) and subsequently taken up in the same buffer in 1 % of the original culture volume . in order to produce the vesicles , 90 % glycerol was added to this at a final concentration of 30 % in three steps at 5 minute intervals . the cells loaded with glycerol were centrifuged ( 1200 × g for 10 minutes , 4 ° c .) and the supernatant was discarded . lysis buffer ( ca . 1 % of the original culture volume ; 10 mm tris / hcl , ph 7 . 4 , 1 mm mgcl 2 , 1 mm cacl 2 ) was added to the cell sediment while mixing vigorously and incubated for 5 min in ice water . this was followed by several centrifugation steps in which cell debris was removed and the vesicle fraction concentrated . a first centrifugation was carried out at 700 × g for 10 min . the supernatant was subjected to a second centrifugation at 700 × g for 10 min , the precipitate was discarded . the precipitate of the second centrifugation was also discarded and the centrifugation was carried out again . the precipitate was again discarded and the remaining supernatant was subjected to a centrifugation at 2300 × g for 10 min . this supernatant was used to bring the vesicles into the precipitate in a last centrifugation of 4500 × g for 10 min . the suspended precipitate was filtered once again through a 5 μm filter and used subsequently . in order to examine the stimulating property of the vesicles obtained in this manner , these were used in a stimulation preparation which was carried out as described above . for this vesicles were obtained from 1 × 10 8 hb 654 cells as described above , these were subsequently used to condition peripheral blood lymphocytes ( 2 × 10 7 cells after treatment with leucyl - leucine methyl ester ). the procedure was exactly the same as described in examples 2 and 3 . in order to evaluate the results , a test for “ kill activity ” was carried out . this test was carried out as described in example 3 . in this procedure the killer t cells produced in the above manner were used as effector cells and the t cell tumour line molt 4 was used as the target cell . in order to quantify the lysis rate of the target cells , the “ cellular dna fragmentation elisa - kit ” from boehringer mannheim gmbh was used for this . the procedure was as stated in example 4 . the result of the test is given in fig2 . it turned out that the blasts formed by the vesicles had killer t cell activity . the blank value described in fig2 corresponds to an absorbance of the reagent without addition of cells . the measured value for spontaneous release corresponds to an absorbance which was obtained when target cells were added without effector cells . production of killer t cells by an eluate from the stimulator cell line which is produced by incubation with a suitable buffer a method described in the following was used as a further method to obtain subcellular fragments which are suitable for producing the claimed effect . cells of the stimulator cell line hb 654 which had been cultured according to the methods stated in the other examples were washed three times in hanks balanced salt solution ( hb ss , boehringer mannheim gmbh , ger ) and subsequently taken up in 150 mmol / l nacl , 15 mmol / l na - citrate , ph 7 . 2 at a density of about 2 × 10 7 cells / ml . they were subsequently incubated for 30 min at 37 ° c . afterwards the cells were sedimented by a centrifugation for 7 min at 4500 × g . the supernatant obtained in this manner represents the eluate . the supernatant is filtered once again through a 5 μm filter and used subsequently . in order to examine the stimulating property of the eluate obtained in this manner , this was used in a stimulation preparation which was carried out as described above . for this eluate was obtained as described above from 2 × 10 7 hb 654 cells , and this was used subsequently to condition peripheral blood lymphocytes ( 2 × 10 7 cells ). the procedure was as described in the previous example . a test for “ kill activity ” was carried out to evaluate the results . this test was carried out as described in the previous examples . for this the killer t cells produced in the above manner were used as effector cells and jurkat as the target cell . in order to quantify the lysis rate of the target cells , the “ cellular dna fragmentation elisa - kit ” from boehringer mannheim gmbh was used for this . the procedure was as stated in example 4 . it turned out that the blasts formed by the eluate had killer t cell activity . absorbances for brdu release ( after subtracting the absorbance for spontaneous release ) of 0 . 121 , 0 . 214 , 0 . 269 and 0 . 114 were obtained with four different vesicle preparations .
the present invention concerns a mammalian cell line which when co - cultured with lymphocytes during which allogenic stimulation is avoided activates lymphocytes fo form tumoricidal cells , a process for the production of tumoricidal t lymphocytes by co - culturing lymphocytes with this cell line , the tumoricidal t lymphocytes obtained by means of this process and the use of the cells according to the present invention for the production of a therapeutic agent which can be used in tumour therapy .