Bone marrow transplantation with interleukin-2-activated bone marrow followed by interleukin-2 therapy for acute myeloid leukemia in mice

We have investigated approaches to induce graft-versus-leukemia (GVL) effect in autologous bone marrow transplantation (ABMT) without graft-versus-host disease to improve survival and cure in leukemia. The present study shows that bone marrow transplantation (BMT) using syngeneic bone marrow activated with interleukin-2 (ABM) for 24 hours in vitro, followed by interleukin-2 (IL-2) therapy, was superior to BMT with fresh, syngeneic bone marrow (FBM) in terms of survival and cure in mice with acute myeloid leukemia (P less than .001) and led to normal hematopoietic reconstitution. Addition of IL-2 therapy after BMT with FBM did not improve the results over BMT with FBM alone (P = .98). These results suggest that the GVL effect of ABMT can be enhanced by using ABM for BMT followed by IL-2 therapy without compromising engraftment.

A novel approach to purging of leukemia by activation of bone marrow with interleukin 2

The cytotoxic potential of interleukin 2 (IL-2) activated bone marrow (ABM) was compared with that of IL-2 activated peripheral blood lymphocytes (LAK cells) against three hematologic tumor cell lines (K-562, CEM, Daudi) and fresh lymphoid blasts in short-term chromium release assays. ABM was found to be superior to LAK cells against all tumor cells tested. The recovery of bone marrow (BM) cells dropped with passage of time in culture but their clonogenic potential was not impaired (with or without IL-2). BM contaminated with CEM cells and treated with IL-2 showed significant ability to purge itself of the leukemic cells in semisolid agar culture; the purging ability of 3- and 1-day ABM was comparable. IL-2 alone or BM alone had no influence on the growth of CEM cells. This study suggests that BM can be activated with IL-2 in vitro to generate the ability to eliminate contaminating leukemic cells without affecting its progenitor cell function in vitro.

Local production of tumor necrosis factor and IFN-gamma in tuberculous pleuritis

TNF and IFN-gamma are thought to be involved in the immune response to mycobacterial infection because they exhibit antimycobacterial effects in vitro. To investigate the roles of these cytokines in vivo at the site of disease activity in human tuberculosis, we evaluated local cytokine production in patients with tuberculous pleuritis. Both TNF and IFN-gamma were selectively concentrated 5- to 30-fold in pleural fluid, compared to blood of the same patients. Messenger RNA for both cytokines was detected in pleural tissue by in situ hybridization, suggesting that selective cytokine concentration is due to local cytokine production. Two Mycobacterium tuberculosis cell wall components, the protein-peptidoglycan complex and lipoarabinomannan, caused dose-dependent release of TNF by pleural fluid mononuclear cells and may constitute the stimuli for TNF production in the pleural space. In contrast to results obtained for TNF release, the protein-peptidoglycan complex, but not lipoarabinomannan, stimulated IFN-gamma release by pleural fluid mononuclear cells. The clinical manifestations of tuberculous pleuritis, such as fever, exudative pleural effusion, and tissue necrosis, may be due to the effects of elevated local TNF concentrations, produced in response to mycobacterial cell wall components.

Local production of tumor necrosis factor and IFN-gamma in tuberculous pleuritis

TNF and IFN-gamma are thought to be involved in the immune response to mycobacterial infection because they exhibit antimycobacterial effects in vitro. To investigate the roles of these cytokines in vivo at the site of disease activity in human tuberculosis, we evaluated local cytokine production in patients with tuberculous pleuritis. Both TNF and IFN-gamma were selectively concentrated 5- to 30-fold in pleural fluid, compared to blood of the same patients. Messenger RNA for both cytokines was detected in pleural tissue by in situ hybridization, suggesting that selective cytokine concentration is due to local cytokine production. Two Mycobacterium tuberculosis cell wall components, the protein-peptidoglycan complex and lipoarabinomannan, caused dose-dependent release of TNF by pleural fluid mononuclear cells and may constitute the stimuli for TNF production in the pleural space. In contrast to results obtained for TNF release, the protein-peptidoglycan complex, but not lipoarabinomannan, stimulated IFN-gamma release by pleural fluid mononuclear cells. The clinical manifestations of tuberculous pleuritis, such as fever, exudative pleural effusion, and tissue necrosis, may be due to the effects of elevated local TNF concentrations, produced in response to mycobacterial cell wall components.

Hemolytic anemia in a cancer patient treated with recombinant interferon-gamma

Currently, three classes of interferon are used in the treatment of malignancies. Interferon-gamma is the best studied. Bone marrow suppression as well as immune hemolytic anemia have been described. Heretofore, only bone marrow suppression has been attributed to interferon-gamma (IFN gamma). In this report, we describe a woman with lung cancer being treated with IFN gamma in whom acute hemolytic anemia occurred. Immune hemolysis did not appear to be the cause. We concluded that in addition to bone marrow suppression, hemolysis should be considered in a patient receiving IFN gamma in whom an unexplained drop in hematocrit occurs.

Heterogeneity of cell surface structures involved in cytotoxicity mediated by lymphokine activated killer cells

Lymphokine activated killer (LAK) cells mediate the lysis of a variety of histologically distinct tumor targets. We investigated the nature and diversity of the structures involved in the recognition phenomenon by evaluating the effects of treating effector and target cells with trypsin and chymotrypsin, enzymes that disrupt surface protein molecules. Chymotrypsin and trypsin treatment of B16 target cells, a murine melanoma cell line, significantly abolished killing by LAK cells. Alternatively, neither of these treatments in P815 cells, a murine mastocytoma cell line, affected killing by LAK cells. Moreover, we found a differential effect of both these enzymes on YAC-1 cells, a murine leukemia cell line, with trypsin having a less inhibitory effect on cytolysis than chymotrypsin. The nature of the LAK cell receptor that presumably plays a role in binding target antigen was also investigated. Treatment of LAK cells with chymotrypsin significantly reduced lysis of the B16 and YAC-1 target cell types. However, trypsin treatment of the effectors only inhibited killing of the B16 tumor cell line. Cytotoxicity exerted against YAC-1 remained unaltered upon trypsinization of LAK cells. These cumulative results indicate heterogeneity of both the receptors on the LAK cells and the surface antigen molecules recognized on these targets. The use of YAC-1 as a target provided us with a tool to compare the LAK with the natural killer (NK) systems. The overall effect of proteolytic enzyme treatment in reducing cell lysis was more pronounced in the NK than in the LAK system.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Fish and Plankton on Lake Temperature and Mixing Depth

A comparative study of small temperate lakes (<20 square kilometers) indicates that the mixing depth or epilimnion is directly related to light penetration measured as Secchi depth. Clearer lakes have deeper mixing depths. This relation is the result of greater penetration of incident solar radiation in lakes and enclosures with high water clarity. Data show that light penetration is largely a function of size distribution and biomass of algae as indicated by a relation between the index of plankton size distribution (slope) and Secchi depth. Larger or steeper slopes (indicative of communities dominated by small plankton) are associated with shallower Secchi depth. In lakes with high abundances of planktivorous fish, water clarity or light penetration is reduced because large zooplankton, which feed on small algae, are reduced by fish predation. The net effect is a shallower mixing depth, lower metalimnetic temperature and lower heat content in the water column. Consequently, the biomass and size distribution of plankton can change the thermal structure and heat content of small lakes by modifying light penetration.

Generation and characterization of IL-2-activated bone marrow cells as a potent graft vs tumor effector in transplantation

The potential of bone marrow transplantation as an immunotherapeutic modality, using biomodulation of the marrow cells has been ignored in autologous transplantation. Furthermore, many common cancers such as lung, colon, prostate, and pancreas are resistant to even transplant doses of conventional agents and hence require novel approaches such as biomodulation. This study shows that we can generate cytotoxic killer cells similar to lymphokine-activated killer cells capable of lysing NK-resistant tumor cells in vitro if we incubate human or murine bone marrow in IL-2. This was accomplished without affecting the ability of the bone marrow to fully reconstitute mice similar to that of fresh nonactivated bone marrow. Studies evaluating the IL-2 activated human bone marrow in vitro also indicated that these activated bone marrow have similar CFU to that of fresh human marrow. Furthermore, in murine in vivo studies, the activated bone marrow (ABM) caused significant tumor regression in tumor-bearing mice. Also, these ABM cells had similar or higher tumoricidal activity and longer kinetics than spleen lymphokine-activated killer cells in vitro. Also, the ABM had purging ability in vitro. Therefore this IL-2 ABM could be used as an active therapeutic tool and not just as a passive rescue element in the autologous bone marrow transplantation setting.

Potent graft antitumor effect in natural killer-resistant disseminated tumors by transplantation of interleukin 2-activated syngeneic bone marrow in mice

The current study is a continuation of our previous work showing that bone marrow activated in interleukin 2 has antitumor and antiviral activity in vitro. The antitumor efficacy of IL-2-activated bone marrow cells in vivo was assessed here. Our results indicated that bone marrow cells activated in IL-2 for 3 days (ABM) have antitumor activity in vivo and cause significant tumor regression in mice being treated with ABM and concurrent i.p. administration of IL-2. In mice also bearing larger tumor burdens, those receiving ABM and i.p. IL-2 showed the most significant tumor regression. The ABM seem to be more potent than conventional IL-2-activated spleen lymphokine-activated killer cells. In studies done using lower dosages of IL-2 or log lower number of cells, the ABM caused more significant tumor regression than lymphokine-activated killer cells. We also assessed the antitumor efficacy of short term (1 day) IL-2-activated bone marrow, the short term-activated bone marrow being preferred in bone marrow, transplantation because of the minimum amount of cells lost due to its shorter incubation period. We also showed that short term-activated bone marrow caused tumor regression similar to ABM and could reconstitute lethally irradiated mice similar to fresh bone marrow. Therefore, the biomodulation of bone marrow cells could be used as an active therapeutic tool in autologous bone marrow transplantation, producing graft versus tumor effects without any graft versus host effect.

Generation and characterization of IL-2-activated bone marrow cells as a potent graft vs tumor effector in transplantation

The potential of bone marrow transplantation as an immunotherapeutic modality, using biomodulation of the marrow cells has been ignored in autologous transplantation. Furthermore, many common cancers such as lung, colon, prostate, and pancreas are resistant to even transplant doses of conventional agents and hence require novel approaches such as biomodulation. This study shows that we can generate cytotoxic killer cells similar to lymphokine-activated killer cells capable of lysing NK-resistant tumor cells in vitro if we incubate human or murine bone marrow in IL-2. This was accomplished without affecting the ability of the bone marrow to fully reconstitute mice similar to that of fresh nonactivated bone marrow. Studies evaluating the IL-2 activated human bone marrow in vitro also indicated that these activated bone marrow have similar CFU to that of fresh human marrow. Furthermore, in murine in vivo studies, the activated bone marrow (ABM) caused significant tumor regression in tumor-bearing mice. Also, these ABM cells had similar or higher tumoricidal activity and longer kinetics than spleen lymphokine-activated killer cells in vitro. Also, the ABM had purging ability in vitro. Therefore this IL-2 ABM could be used as an active therapeutic tool and not just as a passive rescue element in the autologous bone marrow transplantation setting.

Synergistic antitumor effects of interleukin 2 and the monoclonal Lym-1 against human Burkitt lymphoma cells in vitro and in vivo

Interleukin 2 (IL-2) regulates immune responses by inducing proliferation and differentiation of T-cells into cytotoxic cells, inducing lymphokine activated killer activity and enhancing antibody dependent cellular cytotoxicity (ADCC). Lym-1, a monoclonal antibody, recognizes a membrane antigen present on the surface of B-lymphoma cells and can be used for ADCC. We therefore used Raji (human Burkitt lymphoma) cells to study the efficacy of combination therapy with IL-2, lymphokine activated killer activity, and Lym-1. In vitro ADCC assays using Lym-1 showed that preincubation of peripheral blood lymphocytes with IL-2 had a synergistic antitumor effect. The maximum synergism was achieved when peripheral blood lymphocytes were incubated with IL-2 for 3 days as compared to 1 or 2 days, with the optimal concentration of IL-2 being 1000 units/ml. This effect was specific for Lym-1 as demonstrated by experiments using an irrelevant (antimelanoma) monoclonal antibody or an irrelevant target cell (A375). The ADCC was blocked by an anti-Fe receptor antibody (3G8). In vivo experiments performed by growing Raji tumors in nude mice also demonstrated the increase in ADCC and the synergism between IL-2 and Lym-1 in terms of decreased tumor size and growth. The mechanism of this synergy is probably from activation of cells mediating ADCC. This raises the possibility that treatment of patients with low doses of IL-2 in combination with Lym-1 may enhance immune responses and thereby antitumor activity.

The potential usefulness of interleukin-2 activated bone marrow cells as an active therapeutic tool against cytomegalovirus infection in a bone marrow transplantation setting

Bone marrow transplantation (BMT) has been used in recent years for the treatment of immunodeficiency diseases, aplastic anemia, and leukemia. However, there are a number of serious problems and limitations associated with autologous or allogeneic BMT. One of these is an increase in opportunistic infections, of which cytomegalovirus (CMV) infection is one of the most important. Cytomegalovirus has been associated with more frequent deaths than any other single agent, with no reproducibly successful or therapy currently available. Recently usage of interleukin-2 or immunomodulation has been suggested as a powerful modality to combat infectious disease. In this study we showed that bone marrow activated in interleukin-2 for 2 days has the ability to lyse spleen cells infected for 3 days with murine CMV (acute infection model) or salivary gland cells infected for 7 days (chronic infection model), while nonactivated bone marrow or natural killer (NK) cells showed no such lysis. The majority of activated cells involved in lysis were antiasialo GM1-, Thy-1+/-, indicating a population of cells other than the natural killer-cell population involved.

A phase 1a clinical trial of LYM-1 monoclonal antibody serotherapy in patients with refractory B cell malignancies

Ten patients with refractory B cell lymphomas were treated with weekly intravenous infusions of escalating doses of murine monoclonal antibody (MoAb) LYM-1 over four weeks. LYM-1 is a recently developed IgG2a murine MoAb that recognizes a polymorphic HLA-Dr antigen on surfaces of normal and malignant B cells but does not bind to any other normal tissues. MoAb LYM-1 has several advantages for serotherapy, since the antigen it recognizes is not shed from the cell surface and does not modulate in response to MoAb therapy. Furthermore, in vitro studies have indicated significant anti-tumour activity against lymphoma cell lines. In the current trial, dose-dependent levels of free LYM-1 were detected in the serum of all patients, but penetration of extravascular tumour tissues was poor. No significant toxicity or human anti-mouse antibody responses were observed in any patient. Clinical responses were minor and appeared to correlate with the number of infiltrating T cells seen in the initial lymphoma specimens. LYM-1 appears to be well-tolerated and has demonstrated several potential advantages as a therapeutic agent in patients with lymphoma. The mechanism of anti-tumour effect and plans for further clinical studies are discussed.

Successful therapy of natural killer-resistant pulmonary metastases by the synergism of gamma-interferon with tumor necrosis factor and interleukin-2 in mice

The problem associated with lymphokine (gamma-interferon, interleukin-2, and tumor necrosis factor) therapy in cancer is that high toxic doses of these lymphokines must be administered for any significant antitumor results. Therefore this study was undertaken to investigate the antitumor efficacy of these lymphokines in a disseminated pulmonary metastasis when used in combination with each other at dosages well below the toxic level. The role of the immune system of the host, sequencing of lymphokines, and histopathological aspects of lymphokine therapy were also investigated.

Therapy of disseminated NK-resistant tumor by the synergistic effects of recombinant interleukin-2 and tumor necrosis factor

Tumor necrosis factor and interleukin-2 each in recombinant form have antitumor activity against established tumors if used in high enough dosages. The problem associated with such high dosages is the high degree of toxicity and expense encountered. Therefore, this study was undertaken to look at the antitumor efficacy of these two lymphokines when used together at dosages well below the toxic levels. Our results using recombinant human interleukin-2 (IL-2) and recombinant human tumor necrosis factor (TNF) against established methylcholanthrene-induced fibrosarcoma (MCA sarcoma) pulmonary metastases showed that TNF and IL-2 therapy at low nontoxic dosages alone did not produce significant tumor regression, but when combined at the same dosage synergize producing significant antitumor effects in mice induced with MCA sarcoma. This was also evident from histopathological examination of the lungs where the maximum tumor reduction along with the maximum lymphocytic infiltration into tumor was seen when TNF and IL-2 were combined. In this tumor regression, inherent immunity of the treated mice was needed, since in those mice in which we induced immunosuppression by using radiation, tumor regression was not seen when TNF and IL-2 therapy was combined in the doses efficacious in immunocompetent mice. Tumor regression is also dependent on the sequence of administration of IL-2 and TNF, since when IL-2 was administered before TNF, the tumor regression was more significant than when TNF was administered before IL-2 or when both were administered simultaneously to mice with established pulmonary tumors. Therefore the synergistic effect of IL-2 and TNF could be used as an efficacious but inexpensive and nontoxic alternative to therapy with lymphokine activated killer (LAK) cells + IL-2.

Lysosome rich cells contain the lytic activity of lymphokine-activated killer cell populations

Little is known regarding the effectors of lymphokine-activated killer activity. Lysosomotropic agents such as quinacrine can be used to positively sort for lysosome rich cells in natural killer (NK) cell populations. We therefore decided to use this agent to sort lymphokine-activated killer (LAK) cells to characterize their lysosomal content. We found that the positively sorted population contained all the LAK activity, i.e., lysis of NK-resistant tumor cells (B16 melanoma cell line), with the negatively sorted cells having no killing activity. Therefore separation of interleukin-2-incubated cells for LAK activity could be accomplished using sorting after quinacrine staining. The treatment of positively sorted LAK cell populations with L-leucine methyl ester, a lysosomotropic dye which inhibits killing by lysosome rich cells, caused abrogation of killing of the B16 tumor by the treated populations. Single cell conjugate assays were also done on these sorted cells, with positively sorted cells forming the highest and negatively sorted cells the lowest percent of conjugates. Our data therefore indicates the important role of lysosome rich cells in the LAK cell population in the murine system.

Activation of tumoricidal properties in peripheral blood monocytes of patients with colorectal carcinoma

The purpose of these studies was to determine whether blood monocytes of patients with different stages of colorectal carcinoma could be activated by various immunomodulators to become tumor cytolytic. Monocytes obtained from 12 colorectal carcinoma patients and 8 normal donors were incubated in vitro with free or liposome-encapsulated agents. The cytotoxic properties of the monocytes were determined subsequent to interaction with radioactively labeled allogeneic colon carcinoma cells, melanoma cells, glioblastoma cells, and allogeneic nontumorigenic skin cells. Blood monocytes from normal donors and all colorectal carcinoma patients were activated in vitro to become tumoricidal by immunomodulators in free form or entrapped within liposomes; i.e., the monocytes recognized and lysed tumorigenic cells but not nontumorigenic cells. The tumoricidal activity of monocytes was observed in blood monocytes obtained from patients even after multiple doses of radiotherapy and chemotherapy, and that fact suggests that the in vivo activation of macrophages may be feasible.

Regulation of tubulin by triiodothyronine in hypothyroid rat brain

The effect of T3 (triiodothyronine) on the induction of tubulin in hypothyroid developing rat brain has been examined using organ cultures of brains from late fetal, neonatal and postnatal rats. The neonatal brain displayed maximum sensitivity to T3. Hypothyroidism resulted in a 26% decline in the level of tubulin in the neonatal brain as opposed to a 5-15% decline in the fetal or postnatal brain. Exposure of the hypothyroid neonatal brain to T3 for 2 h in culture led to a 61% rise in the level of tubulin in contrast to a 41% increase seen in the case of normal brain. Total protein synthesis was not significantly affected. The preferential decline of tubulin in the neonatal hypothyroid brain, its enhanced sensitivity to T3 compared to normal brain, and the coincidence of the period of sensitivity to that of brain maturation indicate that the regulation of the level of tubulin by T3 in the developing brain is a natural ontogenic phenomenon.

Phase I study of the adoptive immunotherapy of human cancer with lectin activated autologous mononuclear cells

In previous in vitro studies, the authors showed that phytohemagglutinin (PHA) stimulated peripheral blood lymphocytes (PBL) from cancer patients to generate cells that were lytic for fresh autologous tumor but not for lymphocytes or lymphoblasts. Thus, after IRB approval, a phase I clinical protocol was instituted in cancer patients who had failed all other therapy to determine the toxicity and effects, in vivo, of the infusion of large numbers of such PHA activated autologous PBL. Ten patients were treated on the protocol, six with sarcoma, one with melanoma, and three with colorectal cancer. Up to a total of 1.7 X 10(11) PBL were obtained from 7 to 15 successive leukaphereses, the cells from each leukapheresis being incubated in vitro in medium containing PHA and human AB serum for 2 days and then reinfused following the next leukapheresis 2 days later. Toxicity encountered included fever and chills in 10/10 patients, headaches in 5/10, nausea and vomiting in 3/10, and requirement for erythrocyte transfusion in 8/10. No evidence for autoimmune disease, abnormal serum chemical or coagulation studies, or pulmonary emboli was found. 111Indium trafficing studies showed distribution of infused cells mainly to the spleen and liver, with some accumulation in the lungs and tumor especially after repeated infusions. In 9/10 patients, activated PBL were detected in the peripheral circulation by the sixth leukapheresis. Evidence for this was found by assaying the incorporation of tritiated thymidine (3H-Tdr) into, and lysis of fresh tumor cells by, unstimulated PBL from successive leukaphereses. No tumor regression was seen in these patients with bulk disease. These studies demonstrated that large numbers of PHA-activated PBL can be safely obtained and infused into humans, achieving an increase in the number of circulating activated cells with evidence of migration of cells to tumor, lungs, liver and spleen. Further studies of the use of activated lymphocyte infusion in conjunction with chemotherapy in humans are in progress.

Successful immunotherapy of natural killer-resistant established pulmonary melanoma metastases by the intravenous adoptive transfer of syngeneic lymphocytes activated in vitro by interleukin 2

In previous in vitro studies, we have shown that murine splenocytes or cancer patient lymphocytes incubated in IL-2 become lytic for fresh syngeneic or autologous tumors. We have now performed the adoptive transfer of such lymphokine-activated killer (LAK) cells in a murine B16 metastasis model to test their in vivo efficacy. 1 X 10(8) LAK cells, infused intravenously into C57BL/6 mice with established B16 pulmonary metastases, led to a marked decreased in the number of lung nodules and improved survival. LAK cells administered 3 d after amputation of a tumor-bearing limb also decreased the incidence of spontaneous pulmonary metastases. LAK cells generated from tumor-bearer splenocytes had effects equivalent to those from normal animals, and this antimetastatic effect of the LAK cells did not require the prior administration of cyclophosphamide or other immunosuppressants. Fresh or unstimulated splenocytes had no effect. The antitumor effectors and precursors in vivo and in vitro were Thy-1+. The lymphokine required for the activation appeared to be interleukin 2 (IL-2), since incubation in partially purified supernatants from PMA pulsed EL-4 or Con A-pulsed splenocytes or purified Jurkat IL-2 led to the generation of LAK cells equally active in vivo. The use of IL-2-activated cells may provide a valuable method for the adoptive therapy of human neoplasms as well.

Lysis of fresh natural killer-resistant tumor cells by lectin-activated syngeneic and allogeneic murine splenocytes

This paper demonstrates that lectin-activated lymphocytes of selected mouse strains can lyse fresh autologous or allogeneic tumor cells but not the fresh normal cells tested in short-term 51Cr release assays. Murine splenocytes, incubated with concanavalin A for 3 days, lysed tumor cells from fresh syngeneic P815 mastocytoma, 102 methylcholanthrene sarcoma, and FBL3 lymphoma; fresh allogeneic 3LL lung carcinoma and MethA sarcoma; and tissue-cultured YAK cells in 18-hr51Cr release assays. Natural killer cells in fresh splenocyte preparations only lysed tissue-cultured YAK cells and not the other targets. Syngeneic and allogeneic lymphoblasts, lung, or liver cells were not lysed by the concanavalin A-activated killer (CAK) cells. The induction of cytotoxicity by concanavalin A incubation was abrogated by alpha-methylmannoside in the 3-day incubation, but not in cytotoxicity assay. Radiosensitive cells and adherent cells were necessary for the generation of CAK cells. The CAK effectors themselves were radioresistant, nonadherent, and mostly Thy 1+ and Ly 2+. The CAK phenomenon may be mediated by lymphokine production by an Ly 1+ cell, since depletion of Ly 1+ cells prior to activation abrogates CAK induction, and the ability of numerous mouse strains (and nude mice) to generate CAK cells correlated with their ability to produce Interleukin 2. The biological and therapeutic role of these cells is currently being investigated in murine syngeneic primary and metastatic tumor models.

Lymphokine-activated killer cell phenomenon. II. Precursor phenotype is serologically distinct from peripheral T lymphocytes, memory cytotoxic thymus-derived lymphocytes, and natural killer cells

Culture of human peripheral blood lymphocytes (PBL) in partially purified and lectin-free interleukin 2 results in the generation of cytotoxic effector cells which have the unique property of lysing natural killer (NK)-resistant fresh human tumor cells. We have termed these effector cells "lymphokine- activated killer" cells (LAK). LAK are generated from both normal and cancer patients' PBL and are able to lyse both autologous and allogeneic tumor cells from all histologic tumor types tested. Our previous studies suggested that the LAK phenomenon was distinct from either the cytotoxic thymus-derived lymphocyte (CTL) or NK systems based on a variety of criteria. This study reports that the cell type involved is also distinct, as determined by phenotypic characteristics. The LAK effector cell phenotype was analyzed in parallel with alloimmune CTL, and LAK were found to be similarly susceptible to the monoclonal anti-T cell antibodies OKT-3 or OKT-8 plus complement. In contrast the LAK precursor was not susceptible to the OKT-3 or Leu-1 antibodies plus complement, while the ability to generate alloimmune CTL was totally obliterated when tested using the same PBL responder population; in fact, generation of LAK was found to be augmented five- to sixfold, clearly suggesting that LAK precursor cells are not T lymphocytes as defined by these antibodies. LAK precursors were found to be abundant in NK cell-enriched Percoll gradient fractions, which had been depleted of the 29 degrees C E- rosetting "high affinity" T cells. However, LAK precursors were found to be distinct from the majority of NK cells since lysis of fresh PBL with the monoclonal antibodies OKM-1, Leu-7, or OKT-11 significantly depleted or totally eliminated NK activity, while subsequent activation of the remaining cells generated high levels of LAK and in some cases augmented levels of LAK. LAK precursors were found to be distributed in the thymus, bone marrow, spleen, lymph node, and thoracic duct in addition to the PBL. Therefore, while the cell(s) responsible for activation and expression of LAK activity have some common features with the classic T cell-mediated CTL and NK cell systems, the LAK precursor cells are clearly distinct as determined by phenotype analysis using monoclonal antibodies and complement, and at present must be classified as a "null" cell.

Characterization of the lysis of fresh human solid tumors by autologous lymphocytes activated in vitro with phytohemagglutinin

Human peripheral blood lymphocytes (PBL), obtained from patients with a variety of malignancies, when incubated in vitro with phytohemagglutinin (PHA), lysed fresh autologous tumors during a short-term 51Cr-release assay. These PHA-activated killer (PAK) cells produced maximum lysis of tumor cells by 4 to 8 hr of co-cultivation. PHA incubation induced the generation of cells lytic for autologous and allogeneic tumors but not autologous or allogeneic PBL. Cold target inhibition studies demonstrated that autologous and allogeneic tumors of various histologic types all shared the determinants recognized by PAK cells. Some adherent cells were necessary for generation of these PAK, but higher numbers were suppressive. Augmentation of tumor cell lysis was seen when adherent cells were partially removed before PHA activation. The PAK effector cell was OKT3+, OKT8+. The precursor cell of the PAK was separated from natural killer (NK) cells on Percoll gradients and was generated from thoracic duct lymphocytes, a population devoid of NK cells. Furthermore, the phenotype of the majority of the precursor cells was OKT3+, OKM1-. Activation by PHA for 2 days was found to be an efficient and convenient method for generating lymphoid cells lytic for fresh autologous human tumor. The biologic and possible therapeutic role of these cells is currently being investigated.

Characterization of the lysis of fresh human solid tumors by autologous lymphocytes activated in vitro with phytohemagglutinin

Human peripheral blood lymphocytes (PBL), obtained from patients with a variety of malignancies, when incubated in vitro with phytohemagglutinin (PHA), lysed fresh autologous tumors during a short-term 51Cr-release assay. These PHA-activated killer (PAK) cells produced maximum lysis of tumor cells by 4 to 8 hr of co-cultivation. PHA incubation induced the generation of cells lytic for autologous and allogeneic tumors but not autologous or allogeneic PBL. Cold target inhibition studies demonstrated that autologous and allogeneic tumors of various histologic types all shared the determinants recognized by PAK cells. Some adherent cells were necessary for generation of these PAK, but higher numbers were suppressive. Augmentation of tumor cell lysis was seen when adherent cells were partially removed before PHA activation. The PAK effector cell was OKT3+, OKT8+. The precursor cell of the PAK was separated from natural killer (NK) cells on Percoll gradients and was generated from thoracic duct lymphocytes, a population devoid of NK cells. Furthermore, the phenotype of the majority of the precursor cells was OKT3+, OKM1-. Activation by PHA for 2 days was found to be an efficient and convenient method for generating lymphoid cells lytic for fresh autologous human tumor. The biologic and possible therapeutic role of these cells is currently being investigated.