Identification of a novel CD56- lymphokine-activated killer cell precursor in cancer patients receiving recombinant interleukin 2.

Circulating lymphokine-activated killer (LAK) cell activity in cancer patients receiving recombinant interleukin 2 (rIL-2) therapy is confined to cells expressing the CD56- surface marker. However, CD56- cells from these patients but not normal individuals have been reported to exhibit LAK cytotoxicity only following in vitro activation with rIL-2. Studies were performed to document the existence of CD56- LAK precursor cells and to phenotypically characterize this population in patients receiving rIL-2 therapy using fluorescence-activated cell sorter-purified CD56- cell subsets. Initial studies confirmed that CD56- cells exhibit NK activity [20 +/- 7 (SE) LU/10(6) cells] but not LAK activity (0 +/- 0 LU/10(6) cells) when evaluated directly from peripheral blood of patients receiving rIL-2. CD56- cells from patients but not normal individuals developed significant LAK cytolytic activity against NK-resistant COLO 205 targets (16 +/- 3 LU/10(6) cells) when cultured for 3 days with 1500 units/ml rIL-2. The CD56- LAK precursor activity was confined to cells expressing a CD56-CD16+ phenotype and a large granular lymphocyte morphology; little or no NK or LAK precursor activity was detectable in CD56-CD5+ T-cells from patients. Phenotypic characterization of CD16+CD56- cells revealed that this population is uniformly CD11a+,CD18+, and CD38+ and is heterogeneous in its expression of CD11b, CD11c, and CD16/Leu 11c. These results indicate that rIL-2 administration induces enhanced LAK precursor activity in a novel population of CD5-CD16+CD56- cells.     

Augmentation of murine lymphokine-activated killer cell induction by a factor produced by Nocardia rubra cell wall skeleton-stimulated T cells

Four-hour exposure of C3H/HeN mouse spleen cells to Nocardia rubra cell wall skeleton (N-CWS) before 4-day culture with a suboptimal dose of human recombinant interleukin 2 (rIL 2) augmented the induction of lymphokine-activated killer (LAK) cell activity, whereas the treatment with N-CWS alone induced no cytotoxicity. In accordance with this, the IL 2 binding activity of spleen cells was augmented by combined stimulation with N-CWS and rIL 2. The augmented cytotoxicity was mediated by Thy-1.2+, Lyt-1.1-, Lyt-2.1- and asialo GM1+ cells. Cell cultures in diffusion chambers revealed that N-CWS-treated spleen cells produced a LAK cell induction-helper factor (LAK-helper factor, LHF) when cultured with rIL 2. The LHF production required Thy-1.2+, Lyt-1.1+, Lyt-2.1+ and asialo GM1- cells, and the coexistence of unstimulated accessory cells was also essential for the LHF production. Cells responding to both LHF and rIL 2 to generate LAK activity were Thy-1.2-, Lyt-1.1-, Lyt-2.1- and asialo GM1+. The culture fluid of spleen cells stimulated with both N-CWS and rIL 2 contained no tumor necrosis factor (TNF) activity, and the additional stimulation with N-CWS caused no production of either IL 2 or interferon (IFN). Murine recombinant interleukin 1 alpha (Mu-rIL 1 alpha) could not replace the augmentative effect of N-CWS on LAK cell induction. These results suggest that in the presence of rIL 2, N-CWS stimulates murine T cells to produce LHF that is probably distinct from IL 1, IL 2, TNF and IFN.     

Long-term interleukin 2-dependent growth and cytotoxic activity of tumor-infiltrating lymphocytes from human squamous cell carcinomas of the head and neck

Tumor-infiltrating lymphocytes (TIL) from 16 squamous cell carcinomas of head and neck (SCCH&N) and four nonsquamous cell carcinomas were studied. By immunoperoxidase staining in situ, the tumors studied were found to be infiltrated mainly by CD2+CD3+ cells, and 30-50% of the T-lymphocytes were HLA-DR positive and transferrin-receptor positive. They also contained scarce NKH1+ cells. When TIL as well as autologous peripheral blood lymphocytes (A-PBL) were cultured in 1,000 U/ml of recombinant interleukin 2 (rIL2), TIL proliferated in all but three cases, and A-PBL proliferated in all but two cases. Frequently, but not always, TIL expanded better than A-PBL. The median expansion for TIL was 100-fold and that for A-PBL was 31-fold in long-term cultures maintained for up to 88 days. TIL obtained from untreated primary SCCH&N were initially delayed for up to 20 days in their proliferative response to rIL2, but then grew well. In contrast, TIL and A-PBL from metastatic SCCH&N either did not proliferate or were delayed in their proliferative response for up to 40 or 50 days. A-PBL, when tested early (days 10-20 in culture), showed the highest cytotoxic activity against cultured and fresh tumor-cell targets, whereas TIL were most active later in culture (days 20-30). On a per culture basis, TIL achieved higher antitumor cytotoxicity than A-PBL. By day 80, lytic activities of most TIL cultures declined to undetectable levels. CD3+Leu19- T-lymphocytes were the major expanding cell population in most TIL cultures. However, these cells were poor mediators of antitumor cytotoxicity in TIL or A-PBL cultures as shown in cell sorting experiments. The antitumor effector cells expressed CD3-Leu19+ and/or CD3+Leu19+ phenotypes. On Giemsa-stained smears, these two types of IL2-expanded effector cells had the morphology of large granular lymphocytes. Our results indicate that TIL from human SCCH&N could be expanded and reach high levels of antitumor effector function in long-term cultures with rIL2.     

Immunomodulatory properties and toxicity of interleukin 2 in patients with cancer

We performed a phase Ia/Ib study of interleukin 2 (IL2) in patients with cancer. Single doses of IL2 from 10(3) units/m2 to 10(7) units/m2 were well tolerated but failed to induce significant immunological changes. Chronic IL2 treatment for 5 days out of 7 for 3 weeks was well tolerated at doses below 10(7) units/m2 and was accompanied by significant immunological changes. Following chronic treatment with intramuscular injections of IL2 at 1 x 10(6) units/m2, we observed augmentation of peripheral blood natural killer activity and induction of peripheral blood LAK activity. Induction of LAK activity was most evident when IL2 was included in the cytotoxicity assay. There was a marked increase in the number of peripheral blood mononuclear cells bearing the Leu-19 marker in association with the observed increases in natural killer and LAK activity. A small percentage of Leu-19+ cells coexpressed CD3. There was heterogeneous expression of the low affinity Fc receptor (CD16). In vivo induced Leu-19+ cells could be divided into two populations, dim and bright, based on the intensity of fluorescent staining with antibodies to Leu-19. The majority of Leu-19 bright cells were CD16- while the majority of Leu-19 dim cells were CD16+. In addition, the intensity of CD16 staining was higher for Leu-19 dim cells than for Leu-19 bright cells. Increases in the amounts of CD38 and CD8 antigens were also observed. Significant increases in serum levels of the soluble IL2 receptor were observed during treatment. One partial remission was noted in a woman with non-Hodgkin's lymphoma.     

Differential activation of lymphokine-activated killer cells with different surface phenotypes by cultivation with recombinant interleukin 2 or T-cell growth factor in gastric cancer patients

Fourteen days' culture of human peripheral blood lymphocytes (PBL) with recombinant interleukin 2 (rIL 2) or T cell growth factor (TCGF) results in the generation of lymphokine-activated killer (LAK) effector cells which have the unique property of lysing natural killer (NK)-resistant human tumor cells, Daudi, as well as NK-sensitive, K562 cells. LAK cells were generated from both normal and gastric cancer patients' PBL. However, LAK cell activities induced by rIL 2 or TCGF decreased with the progress of the tumor growth. In addition, TCGF-induced LAK cell activities were found to be lower than the rIL 2-induced LAK cell activities. Different mechanisms may be involved in the decreases of the rIL 2-induced and TCGF-induced LAK cell activities. This study further demonstrates that the cell types involved are also heterogeneous, as determined by phenotypic characteristics. The LAK-effector cell type was analyzed by two-color flow cytometry. RIL 2-induced LAK cells showed increased proportions of CD4+Leu 8- and Leu 7+CD16-, and a decreased proportion of CD8+CD11- cells, which are believed to be associated with killer T cell functions. In contrast, TCGF-induced LAK cells revealed significantly increased proportions of CD8+CD11- and CD4+Leu8- cells, and a decreased proportion of Leu 7+CD16- cells. Thus, LAK cells with different surface phenotypes were induced by the cultivations with rIL 2 and with TCGF.     

Effect of anti-CD3 antibody on the generation of interleukin-2-activated lymphocytes from tumor tissues of gastrointestinal cancer.

BACKGROUND. The efficiency of anti-CD3 antibody (OKT3) for adoptive immunotherapy using lymphokine-activated killer (LAK) cells generated from tumor-infiltrating lymphocytes (TIL), regional lymph node lymphocytes (RLNL), and peripheral blood lymphocytes (PBL) was investigated. METHODS. TIL, RLNL, and PBL derived from 39 patients with gastrointestinal cancers (16 gastric cancers, 17 colorectal cancers, and 6 esophageal cancers) were cultured for 4 weeks with 200 U/ml of recombinant interleukin-2. To one group, solid-phase 10 micrograms/ml OKT3 was added during the initial culture period (day 2 or 4). Cytotoxicity against K562 cells (NK-like activity) and Daudi cells (LAK activity) and the phenotypes of effector cells generated after culturing for 2-3 weeks were studied. RESULTS. Proliferative responses were significantly increased by OKT3 in each type of effector cell (P less than 0.01); in particular, TIL expanded more by OKT3 than PBL and RLNL (P less than 0.01). The population of CD8+ CD11b- cytotoxic T-cells in OKT3-stimulated groups was significantly larger than that in unstimulated groups (P less than 0.01), whereas no differences were observed with CD4+ cells (helper/inducer T-cells) and CD8+ CD11b+ cells (suppressor T-cells). OKT3 enhanced the NK-like activity of TIL and PBL but did not affect their LAK activity. OKT3 suppressed the NK and LAK activity of RLNL. CONCLUSIONS. OKT3 stimulation did not significantly enhance the LAK activity, but the authors propose that OKT3 could be an effective addition to adoptive immunotherapy using TIL due to an increased proliferation and generation of a large cytotoxic T-cell population.     

Lymphokine-activated killer function following autologous bone marrow transplantation for refractory hematological malignancies

Disease recurrence remains the major factor which limits the success of autologous bone marrow transplantation (ABMT) for refractory hematological malignancies. The administration of interleukin 2 (IL2) with or without ex vivo generated lymphokine-activated killer (LAK) cells represents a potential approach to eradicating residual disease after ABMT. However, since LAK precursor activity is radiosensitive, high dose chemoradiotherapy may abrogate LAK function and preclude clinical responsiveness to IL2 after ABMT. Furthermore, since lymphocyte subsets which mediate LAK activity may recover at different rates after ABMT, LAK cells may be phenotypically and/or functionally altered after ABMT. To determine whether IL2 responsive LAK precursor cells are present in the circulation after ABMT, peripheral blood mononuclear cells (PBMC) from 21 patients with acute leukemia or lymphoma were tested for IL2-inducible LAK activity 17-83 days after ABMT. Cells were cultured with IL2 (1000-2000 units/ml) for 4 or 5 days and then tested for cytolytic activity and/or cell phenotype. LAK activity against the Daudi cell line was detected in every PBMC sample from every patient at every time point tested. The Raji cell line and a fresh allogeneic ovarian carcinoma were also lysed by LAK cells generated after ABMT. In the subgroup of patients transplanted for non-Hodgkin's lymphoma, LAK precursor activity appeared comparable to that of healthy controls. Culture with IL2 resulted in increased mean IL2 receptor expression in lymphocytes from patients after ABMT (3.1-9.9%) and from healthy controls (3.1-12.0%). After culture with IL2, the percentage of cells bearing the natural killer cell-associated Leu-19 determinant was significantly higher in patient PBMC than in normal control PBMC (28.3 versus 8.7%). Positive and negative cell selection by fluorescence sorting after culture with IL2 revealed that most of the LAK activity after ABMT was mediated by the Leu-19+ cells. Although CD5+ T-cells were devoid of LAK activity, a subset LAK effectors was CD8+. Thus, LAK activity is rapidly reconstituted after ABMT and is mediated by cells phenotypically similar to those in normal controls. These results support the feasibility of IL2 +/- LAK as consolidative immunotherapy after ABMT.     

Identification and selection of human lymphokine activated killer cell effectors and novel recycling intermediates by unique light-scattering properties

When peripheral blood lymphocytes (PBL) are incubated with interleukin 2 (IL 2), a novel cytotoxic lymphocyte subpopulation, termed lymphokine activated killers (LAK), arises. LAK are functionally defined as IL 2 responsive cells demonstrating major histocompatibility antigen-unrestricted cell-mediated cytotoxicity against fresh solid tumors and other natural killer cell-resistant and -sensitive tumor targets in the absence of prior antigen priming. Flow cytometric analysis of IL 2 activated PBL using forward and right angle light scatter and fluorescence intensity identified the emergence of a large, optically dense, autofluorescent cell population which paralleled the generation of LAK activity. These unique IL 2 induced lymphocytes have been named giant autofluorescent lymphocytes (GAL). These cells are readily distinguished from the small nonfluorescent lymphocytes (SNL) observed in fresh PBL, unstimulated cultured PBL, and those cells remaining after incubation with IL 2 which have not acquired GAL characteristics. In this investigation, LAK cultures were sorted on days 4, 5, and 6 into GAL and SNL populations and were tested for oncolytic activity against the natural killer-resistant Daudi and RC-1 tumor targets. Against these targets, lymphocytes from non-IL 2 activated PBL or the sorted SNL population expressed less than 2% of the oncolytic activity (measured in lytic units) exhibited by GAL effectors. The SNL and GAL populations were cultured in IL 2 for up to 48 h following the sorting procedure and then reassayed for tumor cytolytic activity. During this culture period, GAL but not SNL continued to express LAK killing against natural killer-resistant tumor targets. Using gamma-irradiation to prevent further cell cycling, it was shown that the functional half-life of the LAK effector was approximately 8.5 h. Therefore, the cytotoxicity expressed by the sorted GAL population after 48 h in culture (equivalent to five functional half-lives) must be expressed by progeny of the originally plated lymphocytes. These results indicate that in addition to the LAK effector, the GAL population contains a self-sustaining, recycling intermediate responsible for generating new LAK. Our data indicate that analysis of IL 2 activated PBL using GAL light-scattering properties has application in phenotyping LAK, monitoring of cellular kinetics, cell sorting, and enrichment of the LAK effector population, and in the clinical monitoring of IL 2 therapy.     

Enhancing effect of pokeweed mitogen on the proliferation and the cytotoxicity of lymphokine-activated killer cells.

In order to obtain more potent lymphokine-activated killer (LAK) cells for use in adoptive immunotherapy, pokeweed mitogen (PWM) was added to the culture medium for the initial 24-48 h of culturing. The proliferation rate of PWM-stimulated LAK cells reached about 1000-fold after 3-week culture. This rate was nearly the same as that of LAK cells stimulated by 10 ng/ml of OKT3, the mouse anti-CD3 monoclonal antibody. However, the cytotoxicity of PWM-stimulated LAK cells was significantly more potent than that of OKT3-stimulated LAK cells. Phenotypic analysis revealed that PWM-stimulated LAK cells were CD3+CD56(+)-dominant while OKT3-stimulated LAK cells were CD3+CD56(-)-dominant. About half of CD3+CD56+ PWM-stimulated LAK cells was CD8+. These results suggest that more efficient adoptive immunotherapy is possible by using high-dose PWM-stimulated LAK cells with more potent cytotoxicity. Interleukin-1 beta and tumor necrosis factor alpha were significantly increased in the culture media after 24-h incubation with 1 micrograms/ml of PWM. Secretion of interferon-gamma was not enhanced by this concentration of PWM within 24 h. Therefore, PWM is considered to activate monocytes or macrophages to produce these cytokines in advance, influencing the proliferation and the cytotoxicity of LAK cells.     

Lymphokine-activated killer activity induced by in vivo interleukin 2 therapy: predominant role for lymphocytes with increased expression of CD2 and leu19 antigens but negative expression of CD16 antigens

The phenotype and function of lymphocytes from cancer patients treated with repetitive weekly cycles of continuous i.v. infusions of recombinant interleukin 2 (IL-2) were examined. Peripheral blood lymphocytes (PBL) obtained after IL-2 therapy showed an increased percentage of cells bearing the CD16 and leu19 markers which are associated with natural killer cells. These PBL mediated significantly increased levels of IL-2-dependent lymphokine-activated killer (LAK) activity against the Daudi cell line. Depletion of CD16+ cells from PBL obtained after in vivo IL-2 caused only slight inhibition of their LAK activity or their proliferative response to IL-2 in vitro. This indicates that CD16+ cells are involved but play only a minor role in these responses. In contrast, depletion of leu19+ cells, from PBL activated in vivo with IL-2, virtually abrogated their LAK activity and their proliferative response to IL-2. Two-color flow cytometry studies showed that a leu19+/CD16- population was expanded by in vivo IL-2 therapy and was responsible for the majority of LAK activity by in vivo-activated PBL. Moreover, this CD16- population showed an increased density of leu19 and CD2 (E rosette receptor) antigens when compared to the resting PBL obtained prior to IL-2 treatment. These data show that the predominant population mediating in vitro LAK activity, induced by in vivo IL-2 therapy, consists of activated natural killer cells with a high density of leu19 and CD2 antigens but negative for the CD16 antigen.     

Fulminant clonal expansion of large granular lymphocytes. Characterization of their morphology, phenotype, genotype, and function

A 39-year-old woman exhibited abrupt malignant transformation of the large granular lymphocytes (LGL) after a chronic course of T gamma-lymphoproliferative disease (T gamma-LPD). The T gamma-lymphocytes were CD2+, CD3-, CD8-, CD16+, Leu7-, and Leu19+ with morphologic characteristics of LGL. Newly appearing LGL were much larger and had more prominent azurophilic granules. Although fundamentally they had the same phenotype as the LGL in chronic stage, they showed increased Ia-like antigen and decreased CD16 antigen expressions. Immunoglobulin (Ig) G-kappa type monoclonal component was detected in the patient's serum. The LGL showed a germ-line configuration for T-cell receptor (TCR) beta and gamma chain genes, whereas the clonal chromosomal abnormalities indicated the neoplastic nature of the LGL. The LGL exhibited competent natural killer (NK), interleukin 2 (IL2) activated killer (AK), and antibody-dependent cell-mediated cytotoxicity (ADCC) activities. The LGL may have derived from NK cells at their mature stage with prethymic phenotype and may have influenced the homeostasis of the patient's humoral immune response.     

Proliferative and/or cytotoxic activity of lymphocyte clones to autologous human melanoma

Peripheral blood lymphocytes (PBL) of a patient with metastatic melanoma were cultured with autologous melanoma cells (Auto-Me) and recombinant interleukin 2 (IL-2) (MLTC-PBL). Thirty-five days later, when no cytotoxicity against Auto-Me or K562 was detectable, MLTC-PBL were cloned in the presence of Auto-Me, IL-2 (25 U/ml) and Daudi cells as feeder. Eighty-one growing clones were simultaneously screened for proliferative and cytotoxic activity to Auto-Me. Twenty-two clones proliferated in the presence of Auto-Me only, 29 in the presence of IL-2 only and 41 in the presence of Auto-Me plus IL-2; 12 clones showed cytotoxic activity against Auto-Me. Six clones expressed both cytotoxic and proliferative activity to Auto-Me. The phenotype of 6 proliferative clones tested was CD3+, CD4+, WT31+, CD8-, CD16-, Leu19-, whereas that of 2 cytotoxic-proliferative clones tested was CD3+, CD8+, Leu19+, WT31+, CD4-, CD16-. Specificity analysis of proliferative response of 6 clones and of cytotoxicity of 7 clones, tested on a panel of 14 different target cells, revealed a complex pattern of reactivity, each clone expressing a peculiar specificity. Our results suggest the possibility of isolating, from melanoma patients' PBL, T-cell clones with proliferative activity to Auto-Me and Auto-Me plus IL-2, and T-cell clones which apparently express both proliferative and cytotoxic activity to Auto-Me.     

Appearance and phenotypic characterization of circulating Leu 19+ cells in cancer patients receiving recombinant interleukin 2

The effects of recombinant interleukin 2 (rIL-2) therapy on peripheral blood mononuclear cells expressing the Leu 19 surface marker were evaluated in 20 cancer patients. Leu 19 is a protein with a molecular weight of 220,000 expressed on 15% of normal peripheral blood mononuclear cells and is found on a majority of cells that mediate non-major histocompatibility complex-restricted cytotoxicity. Increased relative and absolute numbers of circulating Leu 19+ cells were observed in all patients receiving rIL-2. Increases in Leu 19+ cells were due in part to the development of a subpopulation of "bright" Leu 19+ cells (Leu 19b+) that possessed a higher density of membrane Leu 19 antigen than Leu 19+ cells assayed prior to therapy. Further characterization of rIL-2 induced Leu 19+ cells by dual immunofluorescence revealed considerable phenotypic heterogeneity within this population based on the coexpression of "dim" CD8 (CD8d+), CD16, and CD2 markers. The percentage of Leu 19+ CD8d+ cells was increased during rIL-2 therapy and comprised up to 60% of all circulating Leu 19+ cells. CD16+ and CD16- subsets of Leu 19+ cells were also increased by rIL-2. The density of CD16 antigen coexpression varied inversely with the density of Leu 19. Conversely, whereas the percentage of Leu 19 cells coexpressing CD2 was also increased by rIL-2 administration, the density of CD2 antigen expression was higher on the Leu 19b+ subset of cells. The development of circulating lymphokine-activated killer activity in three patients was temporally associated with the development of increased levels of circulating Leu 19+ cells. These studies demonstrate that rIL-2 administration induces preferential increases in cells expressing the natural killer and lymphokine-activated killer cell-associated marker Leu 19 and that these increases are associated with the development of circulating lymphokine-activated killer activity. Furthermore, Leu 19+ cells are comprised of phenotypically heterogeneous subsets which undergo characteristic changes during rIL-2 administration.     

In vitro generation and antitumor activity of adherent lymphokine-activated killer cells from the blood of patients with brain tumors

A procedure for enrichment in recombinant interleukin-2 (rIL2)-activated natural killer (NK) cells was developed and used for in vitro generation of antitumor effector cells from the peripheral blood of 20 patients with central nervous system (CNS) tumors. In comparison to the patients' unseparated mononuclear cells and nonadherent lymphocytes cultured in the presence of 1000 U/ml of rIL2 for up to 3 weeks, interleukin-2-stimulated lymphoid cells, when purified by adherence to plastic, proliferated better (up to 6,720-fold expansion) and achieved up to five times higher levels of antitumor activity against K562 cell targets and NK-resistant glioblastoma cell targets. Two-color flow cytometry analysis showed that cultures of cells purified by adherence to plastic which had the best proliferation contained 10% or less of CD3+Leu19- T-lymphocytes, while the unseparated lymphokine-activated killer cell cultures which proliferated poorly contained up to 85% of CD3+Leu19- T-cells. Cultures of adherent lymphocytes which reached the highest antitumor cytotoxicity were enriched in CD3+Leu19+ effectors (60-80%); the proportion of CD3-Leu19+ NK-cells was not greater than 25% in these cultures. Thus, using the technique of 24- or 48-h activation in rIL2 and adherence to plastic, and in contrast to the results obtained with cells from normal donors, it was not possible to enrich in activated NK cells from the blood of patients with CNS tumors. Instead of activated NK cells, a population enriched in non-major histocompatibility complex-restricted cytotoxic T-cells (CD3+Leu19+) was obtained in cultures from most but not all patients. Low NK cell activity and elevated numbers of circulating CD3+Leu11+ cells seen in the blood of these patients, previously treated by surgery/radiation/chemotherapy and maintained on steroids, could be responsible for the preferential adherence and subsequent expansion to plastic of IL2-activated non-major histocompatibility complex restricted cytotoxic T-lymphocytes.     

Augmentation of lymphokine-activated killer cell cytotoxicity by monoclonal antibodies against human small cell lung carcinoma

This study examined the lymphokine-activated killer (LAK) cell cytotoxicity on monoclonal antibody (MoAb)-bound tumor cells from the human small cell lung carcinoma cell lines H69 and H128. LAK cells were generated from normal peripheral blood mononuclear cells by incubation with interleukin 2 for 3 or more days. Cells from the LAK culture were cytotoxic to natural killer-sensitive (K562, 84% cytotoxicity) and natural killer-resistant (Daudi, 85%; H69 and H128, 69% and 97%, respectively) cell lines, and to freshly excised human lung (49%) and breast (57%) tumors. LAK cytotoxicity to H69 or H128 cells was significantly augmented by target cell preincubation with the small cell lung carcinoma-reactive MoAbs 1096 (increases of up to 271%) or 5023 (up to 223%). SCLC 5023 or 1096 did not enhance LAK cytotoxicity to Daudi cells of lymphoblastoid origin. Pretreatment of LAK cells with an anti-Fc receptor antibody blocked MoAb augmentation by 1096 or 5023 (but not LAK cytotoxicity), suggesting that LAK-MoAb interaction may be mediated by Fc binding. LAK activity coincided with emergence of a large cell [interleukin 2-stimulated large mononuclear leukocyte (LML)] subset expressing the CD16 and NKH-1 surface determinants. Serial immunophenotyping of the LAK cell culture harvested at Days 3, 5, and 7 indicated that the level of LAK cytotoxicity, with or without MoAb augmentation, correlated with frequency of NKH-1-reactive LMLs. These observations support the hypothesis that LAK cytotoxicity is mediated by a NKH-1-reactive LML subpopulation. Antitumor cytotoxicity may be augmented by tumor-reactive MoAbs through Fc binding to this LML subset.     

A unique T-cell line derived from an HTLV-1-negative adult T-cell leukemia patient

A unique T-cell line, designated ATL-5T, was established from lymphoma cells in pericardial effusion of an adult T-cell leukemia (ATL) patient not carrying HTLV-1 provirus. The cell line is OKT4 and/or Leu3a+ and OKT8 and/or Leu2a+, but interleukin 2 receptor (IL2R)- and HTLV-1 provirus genome negative, and has cytogenetically abnormal karyotypes. The cell line contains rearranged T-cell receptor beta-chain gene, which was identical in rearrangement pattern to the T-cell receptor beta-chain gene in primary cells. These results suggest that factors other than HTLV-1 may sometimes be associated with HTLV-1-negative ATL. The ATL-5T cell line we describe here is unique, and should contribute to further elucidation of the mechanisms involved in the pathogenesis of HTLV-1-negative ATL and HTLV-1-positive ATL.     

Enhancing Effect of Pokeweed Mitogen on the Proliferation and the Cytotoxicity of Lymphokine-activated Killer Cells

In order to obtain more potent lymphokine-activated killer (LAK) cells for use in adoptive immunotherapy, pokeweed mitogen (PWM) was added to the culture medium for the initial 24–48 h of culturing. The proliferation rate of PWM-stimulated LAK cells reached about 1000-fold after 3-week culture. This rate was nearly the same as that of LAK cells stimulated by 10 ng/ml of OKT3, the mouse anti-CD3 monoclonal antibody. However, the cytotoxicity of PWM-stimulated LAK cells was significantly more potent than that of OKT3-stimulated LAK cells. Phenotypic analysis revealed that PWM-stimulated LAK cells were CD3⁺CD56⁺-dominant while OKT3-stimulated LAK cells were CD3⁺CD56^--dominant. About half of CD3+CD56+ PWM-stimulated LAK cells was CD8⁺. These results suggest that more efficient adoptive immunotherapy is possible by using high-dose PWM-stimulated LAK cells with more potent cytotoxicity. Interleukin-1β and tumor necrosis factor a were significantly increased in the culture media after 24-h incubation with 1 μg/ml of PWM. Secretion of interferon-γ was not enhanced by this concentration of PWM within 24 h. Therefore, PWM is considered to activate monocytes or macrophages to produce these cytokines in advance, influencing the proliferation and the cytotoxicity of LAK cells.     

Highly oncolytic adherent lymphocytes: therapeutic relevance for leukemia

We have generated and characterized a highly oncolytic adherent lymphocyte subset (A-LAK) from eight leukemic patients with non-lymphocytic leukemia (NLL) in remission and one NLL patient in relapse. Our studies demonstrated that A-LAK was superior in its oncolytic activity (tested in a 3-h 51Cr release assay) to conventionally prepared (LAK) and non-adherent (NA) IL-2 cultures. No activity was observed by this highly oncolytic subset against normal bone marrow (BM). A-LAK also displayed highest proliferative activity in 7-11 day cultures (5- to 58-fold expansion) in comparison to LAK (0.7- to 2.7-fold) or NA (1.0- to 2.6-fold) cultures. Analysis of phenotype of unseparated, NA and adherent (A-LAK) lymphocytes 24 h after IL-2 activation showed that the A-LAK was composed predominantly of high intensity (bright) CD11a+ (LFA-1) lymphocytes (75 +/- 4.8%) when compared to the other two populations (12 +/- 2.1%). Similarly, A-LAK contained higher proportion of CD11b (CR3 receptor)-positive lymphocytes (39 +/- 2.1%) than unseparated and NA lymphocytes (11 +/- 1.4%). Double marker phenotypic studies showed that A-LAK cultures were heterogeneous and distribution of individual lymphocyte subsets differed among NLL patients. While in A-LAK culture of some patients the CD56+, CD3- natural killer (NK) cell subset was predominant, CD3+, CD56- lymphocyte subset was prevalent in others. Highest A-LAK lytic activity was always correlated with highest NK cell content. Characterization studies (using the complement-depletion technique) showed that independently of the distribution of lymphocytes in A-LAK cultures, CD16+, CD56+, CD3- NK cell subset displayed highest oncolytic effect. CD5+ subset also participated in cytotoxic function. These observations indicated that A-LAK may represent a new therapeutic approach to treatment of leukemia.     

Effect of human interleukin 3 on the susceptibility of fresh leukemia cells to interleukin-2-induced lymphokine activated killing activity.

Pretreatment of acute myeloblastic leukemia cells with the hemopoietic growth factor interleukin 3 (IL3) increased their susceptibility to lymphokine activated killing (LAK) but did not affect their constitutive resistance to native natural killer activity. In addition, IL3 treatment did not alter the LAK cell-mediated killing of CD34+ hemopoietic progenitors present in normal bone marrow. Increased 3H-thymidine uptake was generally observed after IL3 treatment. However, failure to proliferate in response to IL3, observed in some cases, did not prevent changes in LAK susceptibility. Enhanced lysis of IL3-treated leukemic cells was accompanied by a moderate increase of the effector-target binding. Increased LAK susceptibility was already observed at 18 h, while optimal cytolysis and expression of the cell adhesion molecule (CAM) LFA-3 (CD58) by IL3-treated AML cells were concomitantly observed at later culture times. In contrast, the CAM ICAM-1 (CD54) was not modulated by IL3, nor were significant changes in the expression of either CAMs observed in normal hemopoietic cells. Blocking experiments with the anti-CD58 monoclonal antibody demonstrated a variable neutralizing effect on the IL3-induced increase of LAK activity, depending on the leukemia cell studied. The effect described here, together with the known role of IL3 in normal hemopoiesis makes it a factor of potential therapeutic value for the treatment of leukemic patients.     

Characteristics of mouse thymocyte-derived, interleukin 2-activated killer cells and their precursors

Culture of hydrocortisone (HC)-resistant C57BL/6 mouse thymocytes with recombinant human interleukin 2 (IL 2) allowed the proliferation of the thymocytes and resulted in the generation of lymphokine-activated killer (LAK) cells cytotoxic to a variety of tumor cells. The cytotoxic activity of the LAK cells was greatly reduced by treatment with anti-Thy 1.2 or anti-Lyt 2.2 monoclonal antibody and complement but not with anti-asialoGM1 antibody plus complement. Fractionation of IL 2-stimulated thymocytes by means of Percoll density gradient centrifugation revealed that both cytotoxic activity and binding capacity to target cells were greater in the cells with lower density and larger size than in the cells with higher density and smaller size. These IL 2-activated thymocytes expressed higher levels of both Thy 1, Lyt 2 and lymphokine-activated cell-associated (LAA) antigens than unstimulated thymocytes, as indicated by a flow cytometric analysis. The frequency of LAK precursor cells was found to be 7.5 times greater in the HC-resistant thymocyte population than in total thymocytes, as determined by means of a limiting dilution method. The LAK precursor cells in HC-resistant thymocytes appeared to be Lyt1- (or dull Lyt 1+), L3T4-, Lyt 2-, asialoGM1-T cells, because elimination of bright Lyt 1+, Lyt 2+ or L3T4+ T cells from HC-resistant thymocytes had no effect on the generation of LAK cells. These results indicate that LAK cells from mouse thymocytes are Lyt 2+ T cells which are inducible from HC-resistant Lyt 2- thymocytes.