Adherent Lymphokine-activated Killer Research Articles

The Proteasome Inhibitor, Bortezomib (Formerly PS-341), Sensitizes Tumor Cells to Adherent Lymphokine Activated Killer (ALAK) Cell-Mediated Killing

The Proteasome Inhibitor, Bortezomib (Formerly PS-341), Sensitizes Tumor Cells to Adherent Lymphokine Activated Killer (ALAK) Cell-Mediated Killing

The effect of phenylacetate on the expansion and cytotoxic activity of adherent lak cells from patients with hepatocellular carcinoma

Objective: To improve the preparation of adherent lymphokine-activated killer (A-LAK) cells and study the synergistic anti-tumor effect of phenylacetate (PA) and A-LAK cells. Methods: A-LAK cells were obtained from peripheral blood mononuclear cells (PBMC) of patients with hepatocellular carcinoma (HCC) by using L-phenylalanine methyl ester (PME) to deplete immunosuppressive monocytes. The proliferation of SMMC7721 cell line treated with PA was studied. A-LAK cells were treated with the supernatant of SMMC7721 cells which had been pretreated with PA and the changes of the proliferation and anti-tumor activity of A-LAK cells were investigated. Results: The expansion of A-LAK cells was significantly higher than that of non-adherent LAK (NA-LAK) cells as well as regular LAK cells. The growth of SMMC7721 cells was significantly suppressed by PA. The supernatant of cultured tumor cells intensively suppressed the proliferation and cytotoxicity of A-LAK cells, but the suppressive effect of supernatant treated with PA previously was decreased. Conclusion: A-LAK cells could be simply prepared by using PME, and showed a synergistic anti-tumor effect with the combination of PA.

Effects of cryopreservation and phenylacetate on biological characters of adherent LAK cells from patients with hepatocellular carcinoma.

To improve the preparation of adherent lymphokine-activated killer (A-LAK) cells and to study the effects of cryopreservation and phenylacetate (PA) on biological characters of A-LAK cells. A-LAK cells were obtained from peripheral blood mononuclear cells (PBMCs) of the patients with hepatocellular carcinoma (HCC) by using L-phenylalanine methyl ester (PME) to deplete immunosuppressive monocytes. Proliferative activity of SMMC7721 cell line after treatment with phenylacetate (PA) was observed. A-LAK cells were treated with the supernatant of SMMC7721 cells that had been pretreated with PA. The changes of proliferation, cytotoxicity and phenotype of A-LAK cells were investigated after cryopreservation. The expansion of A-LAK cells (96.79 +/- 69.10 folds on Day 14) was significantly higher than that of non-adherent LAK (NA-LAK) cells (22.77 +/- 13.20) as well as conventional LAK cells (4.64 +/- 0.91). PA significantly suppressed the growth of SMMC7721 cells, and the inhibitor ratio was 46%. The supernatant of cultured tumor cells intensively suppressed the proliferation and cytotoxicity of A-LAK cells, but the suppressive effect of the supernatant was previously decreased after treatment with PA. Impairments in proliferation and cytotoxicity of A-LAK cells immediately after thawing of cryopreservation and recovery after reincubation with IL-2 were observed. The cytotoxicity of thawed A-LAK cells on Day 5 was significantly higher than that of fresh A-LAK before freezing (54.8 +/- 10.2% vs 40.5 +/- 6.4%). No significant change in the percentage of lymphocyte subsets was identified in frozen A-LAK cells as compared with that in the fresh control cells. A-LAK cells can be simply prepared by using PME, and showed a synergistic anti-tumor effect with the combination of PA. Cryopreservation can increase the immunoactivities of A-LAK cells from the patients with hepatocellular carcinoma.

Generation and Characterization of a Monoclonal Antibody that Recognizes an Activation Antigen Expressed by a Majority of Adherent Lymphokine-Activated Killer Cells

In an attempt to generate murine natural killer (NK) cell-specific monoclonal antibodies (MAbs) by immunizing Balb/c mice with C57BL/6 (B6) A-LAKs, we have isolated a hybridoma, CS/NicT.2, which secretes an IgM that recognizes a majority of B6 and B6 Rag-1-/- A-LAKs. The CS/NicT.2 antigen is highly expressed by A-LAKs, but only at extremely low levels on resting splenocytes, suggesting that its expression is tightly associated with IL-2 activation. Among the cell lines examined, only CTLL-2 expresses the CS/NicT.2 antigen at relatively high levels. A low level of CS/NicT.2 staining is also detected on resting allo-specific cytotoxic T lymphocytes (CTL) clones, AB.1 and C11. In addition, a similar low level of CS/NicT.2 staining is detected on the T-helper cell line HT-2. The CS/NicT.2 antigen is upregulated by ionomycin but not by phorbol 12-myristate 13-acetate (PMA). For the CTL clones examined, CS/NicT.2 staining is also dramatically increased by anti-TCRbeta or anti-CD3epsilon stimulation. Protease treatments of CTLL-2 show that this antigen is proteinase K sensitive, but relatively resistant to trypsin digestion. Furthermore, the CS/NicT.2 antigen exhibits a relatively fast turnover rate as assessed by proteinase K and cycloheximide treatments of CTLL-2, suggesting that the CS/NicT.2 antigen may have a short half-life on the cell surface.

The murine nonclassical class I major histocompatibility complex-like CD1.1 molecule protects target cells from lymphokine-activated killer cell cytolysis.

Classical class I major histocompatibility complex (MHC) molecules, as well as the nonclassical class I histocompatibility leukocyte antigen (HLA)-E molecule, can negatively regulate natural killer (NK) cell cytotoxicity through engagement of NK inhibitory receptors. We show that expression of murine (m)CD1.1, a nonpolymorphic nonclassical MHC class I-like molecule encoded outside the MHC, protects NK-sensitive RMA/S target cells from adherent lymphokine-activated killer cell (A-LAK) cytotoxicity. Passage of effector cells in recombinant interleukin (rIL)-2 enhanced protection by mCD1.1, suggesting an expansion of relevant A-LAK population(s) or modulation of A-LAK receptor expression. Murine CD1. 1 conferred protection from lysis by rIL-2-activated spleen cells of recombination activating gene (Rag)-1(-/-) mice, which lack B and T cells, demonstrating that mCD1.1 can protect RMA/S cells from lysis by NK cells. An antibody specific for mCD1.1 partially restored A-LAK lysis of RMA/S.CD1.1 transfectants, indicating that cell surface mCD1.1 can confer protection from lysis; therefore, mCD1.1 possibly acts through interaction with an NK inhibitory receptor. CD1.1 is by far the most divergent class I molecule capable of regulating NK cell activity. Finally, mCD1.1 expression rendered RMA/S cells resistant to lysis by A-LAK of multiple mouse strains. The conserved structure of mCD1.1 and pattern of mCD1.1 resistance from A-LAK lysis suggest that mCD1.1 may be a ligand for a conserved NK inhibitory receptor.

High expression of NKR-P1 is not an absolute requirement for natural killer activity in BDIX rats.

NKR-P1 has been identified as a triggering structure selectively expressed on rat natural killer (NK) cells and adherent lymphokine-activated killer (A-LAK) cells. In vivo treatment with anti-NKR-P1 monoclonal antibody (mAb 3.2.3) was shown to induce complete inhibition of NK cytotoxicity and elimination of LAK cell precursors in Lewis and Fisher rat strains. We investigated the effects of mAb 3.2.3 in a colon tumor model in BDIX rats. Inoculation of animals with mAb 3.2.3 even at very high doses induced a strong but incomplete inhibition of NK cytotoxicity in nylon-wool-non-adherent spleen and peripheral blood cells. Generation of adherent A-LAK cells from their spleen precursors was also strongly by not fully inhibited. We also investigated the effect of treatment with mAb 3.2.3 on the tumorigenicity of the NK-sensitive REGb cell line. When subcutaneously inoculated in syngeneic animals, REGb cells induce tumors that first grow for 2 weeks, then spontaneously regress and disappear. In contrast with previous results using anti-asialoGM1, no significant difference in tumor growth was observed between rats treated with mAB 3.2.3 and control animals, even with a long-term treatment. In vitro, mAb 3.2.3 exhibited the same incomplete efficiency. Nylon-wool-non-adherent spleen cells treated with mAb 3.2.3 plus complement were completely free of 3.2.3(bright) cells, but retained a substantial NK activity and generated LAK cells after culture with IL-2. After an overnight incubation in standard medium of 3.2.3-depleted spleen cells, 3.2.3(bright) cells were partially recovered and the NK cytotoxic activity, as well as the generation of LAK cells, was significantly enhanced. These results suggest that a strong expression of NKR-P1 is not required for BDIX mononuclear cells to exhibit NK function and generate LAK cells under IL-2 activation.

Enhanced lymphokine-activated killer cell activity by an immunomodulator, Roquinimex

Roquinimex (Roq) is an immunomodulator known to stimulate cellular immune responses. It is currently used for immunotherapy after bone marrow transplantation (BMT). One of the major features of this compound is an enhancement of natural killer (NK) cell activity and numbers. We studied the in vitro effect of Roq on human peripheral blood NK and adherent lymphokine-activated killer cell (ALAK) activities. In cultures supplemented with recombinant interleukin 2 (rIL-2) (1000 U ml-1) and Roq a significant increase in NK and LAK function was observed without a parallel increase in cell numbers. We also examined the generation of NK cells from human bone marrow (BM) immature progenitors, obtained by purging with 4-hydroperoxycyclophosphamide (4HC). NK cell numbers and activity were both increased when cultures with rIL-2 (10 U ml-1) were supplemented with Roq. These results confirm findings obtained in vivo and in vitro in the murine system and suggest that Roq is an active agent on these lymphoid populations. These properties and good tolerability make Roq an attractive tool for immunotherapy.

An evolutionary conserved target cell antigen along with MHC class I molecules influences susceptibility to murine NK cell lysis

We have previously characterized a novel monoclonal antibody (mAb), termed 18C2, which binds to and inhibits the lysis of target cells by human natural killer (NK) cells. We now show that the anti-target cell mAb 18C2 also recognizes a similar structure on the murine NK sensitive target cell YAC-1, as well as on NK resistant target cells P815 and EL-4, as observed by flow cytometry. Functional studies demonstrated that the mAb 18C2 inhibited the lysis of both NK sensitive YAC-1 target cells, as well as NK resistant target cell lines P815 and EL-4 by freshly-isolated nylon wool nonadherent (NWNA) NK cells, 5-day lymphokine activated killer (LAK) cells and adherent lymphokine activated killer (ALAK) cells. The inhibitory activity of the mAb 18C2 occurred at the target cell level only. Single cell conjugate assays as demonstrated that the structure recognized by the mAb 18C2 was involved in recognition between NK cells and NK target cells, as the mAb inhibited conjugate formation between a variety of effector cells and various target cell lines tested. Further, the role of major bistocompatibility complex (MHC) class I antigens in NK cell cytotoxicity was examined. We observed that target cells expressing low levels of MHC class I antigens in association with the novel target cell antigen were more sensitive to NK cell lysis, as compared to cells that co-express higher levels of MHC class I antigen and the target cell antigen. Further, the presence of this antigen across different species suggests this target cell antigen/structure to be highly evolutionarily conserved.

Loco-regional immunotherapy with recombinant interleukin-2 and adherent lymphokine-activated killer cells (A-LAK) in recurrent glioblastoma patients

Loco-regional immunotherapy with recombinant interleukin-2 and adherent lymphokine-activated killer cells (A-LAK) in recurrent glioblastoma patients

Evolutionary Conservation of a Human Function‐Associated Molecule on Murine Natural Killer Cells: Expression and Function

Using a novel anti-natural killer (NK) cell monoclonal antibody (MoAb), we have recently identified an evolutionary conserved function-associated molecule (FAM) present on fish, rat and human NK cells. This molecule is involved in NK cell function as anti-FAM MoAbs inhibit cytotoxicity, stimulate lymphokine secretion and inhibit conjugate formation between effector cells and target cells. We now have examined murine NK cells for the presence of this structure. It was observed by two-colour flow cytometric analysis that the anti-FAM MoAb 5C6 specifically bound to a subpopulation of nylon wool non-adherent splenic lymphocytes (19-20%). The expression of the FAM molecule was restricted to NK cells that expressed the NK1.1 antigen. Neither T cells, B cells, nor macrophages reacted with the anti-FAM MoAb. Analysis of FAM expression in various lymphoid tissues revealed that splenocytes expressed the greatest numbers of MoAb(+) cells. Generation of lymphokine-activated killer (LAK) cells and adherent lymphokine-activated killer (ALAK) cells resulted in higher levels of FAM expression. The anti-FAM MoAb 5C6 also detected the presence of FAM on fresh SCID NK cells. It was demonstrated that the anti-FAM MoAb 5C6 inhibited the lysis of target cells by endogenous NK cells, activated NK cells, 5d LAK cells, ALAK cells and SCID NK cells. Moreover, conjugate assays demonstrated involvement of this molecule in recognition between NK cells and target cells.

Tumor-derived transforming growth factor-beta 1 and interleukin-6 are chemotactic for lymphokine-activated killer cells.

Adherent lymphokine-activated killer (A-LAK) cells are purified IL-2 activated natural killer (NK) cells with potent anti-tumor cytotoxic activity. They have been used in the adoptive immunotherapy of metastatic cancers. However, it has been shown that intravenously transferred LAK cells have a poor homing capacity to tumor sites. For the present study, the effects of tumor-derived factors on the in vitro migratory capacity of A-LAK cells was investigated. In a micropore migration assay the conditioned medium from 3LL Lewis lung carcinoma cell cultures was found to exert a strong chemotactic, but not chemokinetic effect on A-LAK cells. This effect was partially inhibited by neutralizing antibodies against the cytokines TGF-beta 1 and IL-6. A combination of the 2 antibodies completely suppressed the chemotactic activity of tumor-cell-conditioned medium. Purified TGF-beta 1 and recombinant IL-6 were chemotactic for A-LAK cells. Biological activities of both cytokines were detectable in the tumor-cell-conditioned medium. The in vivo relevance of these findings, with respect to tissue infiltration of NK cells and LAK cells in inflammation or cancer, remains to be elucidated.

Cloning and characterization of the 2B4 gene encoding a molecule associated with non-MHC-restricted killing mediated by activated natural killer cells and T cells.

We have recently described a signal transducing molecule, 2B4, expressed on all NK and T cells that mediate non-MHC-restricted killing. The gene encoding this molecule was cloned and its nucleotide sequence determined. The encoded protein of 398 amino acids has a leader peptide of 18 amino acids and a transmembrane region of 24 amino acids. The predicted protein has eight N-linked glycosylation sites, suggesting that it is highly glycosylated. Comparison of 2B4 with sequences in the databanks indicates that 2B4 is a member of Ig supergene family, and it shows homology to murine and rat CD48 and human LFA-3. Northern blot analysis has shown at least three transcripts for 2B4 in adherent lymphokine-activated killer cells of several mouse strains and TCR-gamma/delta dendritic epidermal T cell lines but not in allospecific T cell clones. These three mRNA are the products of differential splicing of heterogeneous nuclear RNA. Southern blot analysis of genomic DNA from several mouse strains revealed that 2B4 belongs to a family of closely related genes. The 2B4 gene has been mapped to mouse chromosome 1 by analysis of 2B4 expression in recombinant inbred mouse strains.

Factors, including transforming growth factor beta, released in the glioblastoma residual cavity, impair activity of adherent lymphokine-activated killer cells.

Adherent lymphokine-activated killer (A-LAK) cells were obtained from peripheral blood lymphocytes of patients with recurrent glioblastoma. In vitro features of A-LAK cultures were assessed in comparison to those of non-adherent lymphokine-activated killer (NA-LAK) cells of the same patients with regard to cytotoxic activity, proliferation and surface markers. Only in a minority of cases did A-LAK cells show a markedly higher cytotoxicity on K562, Daudi and allogeneic glioblastoma cells. Nevertheless, A-LAK cells proliferated significantly better than NA-LAK and contained higher percentages of CD16+, CD56+ and CD25+ cells, indicating that A-LAK cells from these patients represent a subpopulation of lymphocytes enriched for activated natural killer cells. We also investigated whether immunosuppressive factor(s) were present in the tumour bed of recurrent gliomas. To this end, samples of glioblastoma cavity fluid (GCF), which accumulates in the cavity of subtotally removed tumour, were recovered and tested for the presence of immunosuppressive activity. All GCF samples analysed were shown to inhibit in vitro proliferation and antitumour cytotoxicity of 1-week-cultured A-LAK cells in a dose-dependent manner. Such GCF activity was effectively antagonized by a transforming growth factor beta (TGF beta) neutralizing antibody, indicating the involvement of TGF beta in lymphocyte inhibition. These results show that in the tumour cavity remaining after subtotal glioblastoma resection a marked immunosuppressive activity, probably due to local release of TGF beta, is present; such activity may negatively influence the therapeutic effectiveness of local cellular immunotherapy.

The development and purification of a bispecific antibody for lymphokine-activated killer cell targeting against the rat colon carcinoma CC531.

In vivo targeting of lymphokine-activated killer (LAK) cells to tumour deposits by bispecific monoclonal antibodies (bimAb) may be a way to improve adoptive immunotherapy. We developed a bimAb against adherent LAK (ALAK) cells and colon tumour CC531 in Wag rats. The bimAb was produced by somatic hybridization of two mouse hybridomas, one producing monoclonal antibodies (mAb) against CD8 (IgG2b, OX8), and the other producing mAb against a CC531-associated antigen (IgG1, CC52). A bimAb-producing clone was selected by an enzyme-linked immunosorbent assay with CC531 tumour cells. BimAb were purified from ascitic fluid by protein A affinity chromatography. Each of five pooled peak fractions was analysed by flow cytometry for the presence of bimAb. Most bimAb were found in a fraction that was eluted at pH 4.5 from protein A. FPLC analysis of this fraction revealed that no parental antibodies were present. The OX8 x CC52 bimAb greatly increased conjugate formation in vitro between ALAK cells and CC531. Results of 51Cr-release assays with CC531 as target cells and ALAK cells as effector cells were not significantly different in the presence or in the absence of the bimAb. The methods we used here, a cell enzyme-linked immunosorbent assay and flow cytometry, are simple methods for development and purification of a bimAb when a functional selection method is not a priori available. The OX8 x CC52 bimAb we developed this way may increase in vivo tumour targeting of ALAK cells and thus augment antitumour effect in vivo.

Drug resistance in rat colon cancer cell lines is associated with minor changes in susceptibility to cytotoxic cells.

The development of resistance to anticancer drugs urges the search for different treatment modalities. Several investigators have reported the concomitant development of drug resistance and resistance to natural killer (NK), lymphokine-activated killer (LAK) or monocyte/macrophage cell lysis, while others described unchanged or even increased susceptibility. We investigated this subject in the rat colon carcinoma cell line, CC531-PAR, which is intrinsically multidrug-resistant (MDR), and in three sublines derived from this parental cell line: a cell line with an increased MDR phenotype (CC531-COL), a revertant line from CC531-COL (CC531-REV), which demonstrates enhanced sensitivity to anticancer drugs of the MDR phenotype, and an independently developed cisplatin-resistant line (CC531-CIS). In a 4-h 51Cr-release assay we found no difference in susceptibility to NK cell lysis. No significant differences in lysability by adherent LAK (aLAK) cells were observed in a 4-h assay. In a prolonged 20-h 51Cr-release assay an enhanced sensitivity to aLAK-cell-mediated lysis was observed in the revertant, P-glycoprotein-negative cell line and in the cisplatin-resistant cell line (CC531-CIS). None of the cell lines was completely resistant to lysis by aLAK cells. Therefore, a role for immunotherapy in the treatment of drug-resistant tumors remains a realistic option.

Human lymphokine-activated killer cells are cytotoxic against cells infected with Toxoplasma gondii.

Experiments were conducted to determine whether human lymphokine-activated killer (LAK) cells are cytotoxic against cells infected with Toxoplasma gondii. Nylon wool nonadherent (NWNA) peripheral blood lymphocytes, as well as purified natural killer cell (NK) (CD3- CD16+ CD56+) and T (CD3+ CD16- CD56-) cells obtained from five healthy T. gondii seronegative volunteers exhibited minimal cytotoxic activity against T. gondii-infected cells. When standard LAK (S-LAK) cell preparations were induced by incubation of NWNA cells with recombinant interleukin 2, induction of remarkable cytotoxic activity against T. gondii-infected cells. When standard in LAK cell preparations from each of the volunteers. The phenotype of the LAK precursor and effector cells varied depending on the target cell used. Whereas the precursor and the effector cells of most of the LAK activity against K562 and Daudi cells were cells with NK phenotype, when T. gondii-infected cells were used as targets, both cells with NK and T cell phenotypes were precursors and effectors of the lysis. When cytotoxic activity of S-LAK cells was compared with the activity of adherent LAK (A-LAK) cells, A-LAK cells displayed higher cytotoxic activity against T. gondii-infected cells, as well as against K562 and Daudi cells. Cold target inhibition experiments suggested that there is a subset of LAK effector cells capable of lysing both T. gondii-infected cells and Daudi cells, whereas other subsets preferentially or exclusively lyse one of these target cells.

A rapid and sensitive fluorometric microassay for determining cell mediated cytotoxicity to adherent growing cell lines

In order to measure cell mediated cytotoxicity to adherent growing cell lines in vitro more rapidly and conveniently, a fluorometric microassay was developed and results were compared with those obtained by the 51Cr release assay. The fluorometric method is based on the hydrolysis of the fluorochrome 4-methylumbelliferyl heptanoate (MUH) by intracellular esterases of viable cells. Melanoma cell monolayers were incubated with lymphokine activated killer (LAK) cells for 4 h at various effector: target ( E: T) cell ratios ( E: T = 16, 8, 4, 2:1). Thereafter surviving adherent melanoma cells were stained with MUH for 30 min and fluorescence was measured directly in a 96 well plate reader. For the calculation of LAK cell cytotoxicity fluorescence values were corrected for the number of nonspecifically detached tumor cells during the washes and the number of nonspecifically adherent LAK cells. Using identical target and effector cell preparations both assays showed a nearly proportional increase of percentage cytotoxicity with rising numbers of lymphocytes. Compared with the 51Cr release assay, however, higher cytotoxicity values were obtained with the fluorometric MUH microassay: 57% with MUH versus 26% with 51Cr and 39% versus 14% for cell lines StML-11 and SKMel-28, respectively ( E: T ratio = 16:1). The higher cytotoxicity rates obtained with the fluorometric MUH microassay were not due to the additional 30 min staining with MUH or due to nonspecific hydrolysis of MUH by extracellular esterases released from damaged cells, as could be shown by a series of experiments. In conclusion, a simple and rapid fluorometric microassay has been developed showing reliable reproducibility and a higher sensitivity compared with the 51Cr release assay for the determination of cellular cytotoxicity to adherent growing cell lines, avoiding hazardous radioactive labels.

Tissue distribution of adoptively transferred adherent lymphokine-activated killer cells assessed by different cell labels.

Assessment of the tissue distribution of adoptively transferred adherent lymphokine-activated killer A-LAK) cells by use of 51Cr indicated that these effector cells, after an initial phase in the lungs, distributed in high numbers to liver and spleen (30% and 10% of injected dose, respectively). However, when this experiment was repeated with 125IdUrd as cell label, fewer than 2% and 0.5% of the injected cells distributed into liver and spleen respectively. To analyse this discrepancy, we compared the tissue distribution of 51Cr- and 125IdUrd-labelled A-LAK cells with that indicated by alternative direct visual methods for identification of the injected cells, such as fluorescent dyes (rhodamine and H33342) or immunohistochemical staining of asialo-GM1-positive cells. The number of i.v. injected A-LAK cells found in the liver by all visual methods ranged from 1% to 5% of the injected dose, supporting the data obtained with 125IdUrd, whereas 25%-30% of the 51Cr label was consistently found in this organ. Autoradiography of the liver 24 h after i.v. injection of 51Cr-labelled cells revealed a background activity that was four- to fivefold higher than the control level, indicating substantial non-specific accumulation in the liver of 51Cr released from A-LAK cells. We conclude that 51Cr cannot be reliably used in investigations of cell traffic to the liver because of non-specific accumulation of the 51Cr label, particularly in this organ. In contrast, labelling with 125IdUrd or rhodamine and immunohistochemical staining of asialo-GM1-positive cells appear to be reliable and essentially equivalent methods for investigations of the fate of adoptively transferred A-LAK cells. Using these methods, we found that only few A-LAK cells redistribute to the liver upon i.v., i.e. systemic, injection, whereas 40%-50% of locally (intraportally) injected A-LAK cells remain in the liver for at least 24 h.

Identification and partial characterization of a novel plasma membrane-associated lytic factor isolated from highly purified adherent lymphokine-activated killer cells

We have identified and partially purified a novel cytolytic factor isolated from enriched plasma membranes prepared from highly purified lymphokine-activated killer cells (adherent-LAK, A-LAK cells) and a large granular lymphocytic NK cell leukemia, CRNK-16. The enriched plasma membranes were shown to be physically devoid of lytic granules and contained no detectable pore-forming protein (PFP, perforin) activity. The plasma membrane-associated cytolytic factor (designated M-CTX) was solubilized in biologically active form and was highly lytic to a large panel of target cells in 2- to 4-hr 51Cr release assays. Characteristics of the M-CTX include: (1) it is plasma membrane- not granule-associated; (2) it is not hemolytic and functions in the absence of Ca 2+; (3) nucleated target cells are lysed in 2 to 4 hr at 37 °C but not at 4 °C; (4) it induces apoptotic cell death with nuclear DNA fragmentation and massive membrane blebbing; (5) it is isolated from the plasma membranes of cultured A-LAK cells, a lytically active LGL leukemia (CRNK-16), and fresh spleen cells but not from thymocytes or L929 fibroblasts; and (6) the lytic activity of the partially purified toxin is inactivated by trypsin, serum, and heat, but is not blocked by antibodies that inactivate TNF-α, LT or IFN-γ. Taken collectively, these data suggest that M-CTX may represent a heretofore undescribed membrane-associated toxin possibly involved in contact-mediated cell killing.

Generation of adherent lymphokine activated killer (A-LAK) cells from patients with acute myelogenous leukaemia

Successful generation of adherent lymphokine-activated killer (A-LAK) cells, highly-enriched in CD3-CD56+ antitumour effector cells, from the peripheral blood of ten patients with acute myelogenous leukaemia (AML) is described. The AML patients were either untreated or in remission. In vitro proliferation of A-LAK cells in patients with AML was generally poor, unless the cells were cocultured with irradiated concanavalin A (ConA)--prestimulated allogeneic PBL or selected lymphoblastoid cell lines (LCL) as feeder cells. Using this method, the median fold proliferation was 290 for A-LAK cells cultured with ConA-activated feeders and 291 for those grown with LCL, both significantly higher (both P less than 0.001) than the median of 2-fold expansion observed in cultures without feeders. A-LAK cultures generated in the presence of feeders consistently showed good enrichment (up to 90%) in CD3-CD56+ NK cells. Although NK activity was not significantly increased on a per cell basis in A-LAK cells grown with feeder cells, total lytic activities against both NK-sensitive target, K562, and NK-resistant target, Daudi, were significantly greater (P less than 0.02 for ConA-PBL feeders and P less than 0.005 for LCL feeders) as compared to those in paired cultures without feeders. In the presence of irradiated allogeneic feeder cells, 7/10 AML patients generated A-LAK cultures characterised by good proliferation and increased purity as well as cytotoxic activity.