Anti-CD3 + interleukin-2 stimulation of marrow and blood: comparison of proliferation and cytotoxicity

The proliferation and in vitro cytolytic activity of interleukin-2 (IL-2)-activated and anti-CD3 + IL-2-stimulated marrow mononuclear cells (MMC) and peripheral blood mononuclear cells (PBMC) were studied. Samples from 8 normal donors, 15 patients with acute lymphoblastic leukemia (ALL), and 7 patients with non-Hodgkin's lymphoma (NHL) in remission were cultured in IL-2 (100 U/mL) or IL-2 (100 U/mL) plus anti-CD3 (10 ng/mL). MMC as well as PBMC samples demonstrated significant synergy between IL-2 and anti-CD3 in the promotion of proliferation as measured by 3H thymidine incorporation on day 5 (P less than .001) or fold increase in cell number on day 14. Cryopreserved marrow specimens had equally rapid proliferation as fresh MMC when cultured in the presence of anti-CD3 + IL-2. Anti-CD3 concentrations of 3, 11, 33, and 100 ng/mL augmented proliferation similarly in the presence of IL-2 (0.1 to 100 U/mL). Mean fold increases in cell number of both marrow- and blood-derived cultures after 14 days were significantly higher for anti-CD3 + IL-2-stimulated cultures compared with cultures stimulated with IL-2 only (50- to 200-fold increase in cell number; P = .01). Comparison of remission MMC and PBMC from ALL and NHL patients with normal controls showed equivalent growth rates of activated cultures at 7, 14, and 21 days. Marrow purging with immunotoxin anti-CD19 pokeweed antiviral protein plus 4HC had no significant effect on proliferation of anti-CD3 + IL-2-stimulated MMC cultures in patients with ALL. Cytolytic activity of IL-2- and IL-2 + anti-CD3-activated PBMC and MMC cultures was assessed in 51Cr release assays using K562 (natural killer ([NK]-sensitive), Daudi (Burkitt's lymphoma-, NK-resistant), and Nalm-6 (ALL-, lymphokine-activated killer [LAK]-resistant) cell lines and cryopreserved ALL blasts. Cytolytic activity on a per-cell basis (percent cytotoxicity at an effector:target ratio of 30:1) was similar in IL-2-activated PBMC- and MMC-derived cultures from ALL patients. MMC activated with anti-CD3 plus IL-2 killed Daudi significantly less well than IL-2-activated cultures on days 12 and 19 (P = .03); no significant differences were observed in lysis of LAK-resistant Nalm-6 or cryopreserved ALL blast targets. Dose response of anti-CD3 augmentation of Daudi and Nalm-6 killing was different in IL-2- and IL-2 + anti-CD3-stimulated cultures.(ABSTRACT TRUNCATED AT 400 WORDS)

Depot characteristics and biodistribution of interleukin-2 liposomes: importance of route of administration

Due to rapid clearance of interleukin-2 (IL-2), it has had limited effective use as an in vivo immunostimulant. Current experimental and clinical protocols generally must utilize large doses, multiple injections, or continuous infusions of IL-2 in order to achieve significant immunostimulation, often at the expense of systemic toxicity. Therefore, the pharmacodynamics of IL-2 liposomes were investigated. IL-2 liposome incorporation efficiency was 80.4% (SD 5.5); vesicle diameter was 1.65 microns (SD 0.09) as determined by fluorescence-activated cell sorting (FACS). Both formulation (free cytokine vs. IL-2 liposomes) and route of administration were important variables in determination of the biodistribution and pharmacokinetic characteristics of IL-2. When free [125I]IL-2 was given i.v. to mice, only 6.5% was in the blood and 3% in liver and spleen 2 h after injection; on the other hand, at 2 h greater than 70% of i.v. [125I]IL-2 liposomes were detected in the blood, liver, spleen, and lungs. Mean i.v. elimination t1/2 from the blood of rats given 20 x 10(6) U/kg free cytokine or IL-2 liposomes was 41 versus 102 min, respectively, as measured by bioassay and 59 and 119 min as measured by enzyme immunoassay (EIA). After i.v. administration, the estimated Vd of IL-2 liposomes was 13-fold smaller than the free cytokine. Intrathoracic (i.tx.), i.p., and s.c. administration of [125I]IL-2 to mice also demonstrated significant depot effects when IL-2 was incorporated into liposomes. These data suggest IL-2 liposomes may provide in vivo immunostimulation superior to the free cytokine due to biodistribution and depot characteristics.

Increased circulating nitrogen oxides after human tumor immunotherapy: correlation with toxic hemodynamic changes

BACKGROUND

Toxicity to interleukin-2 (IL-2) tumor immunotherapy is manifested principally by the vascular leak syndrome, hypotension, and a hyperdynamic response with low systemic vascular resistance. Nitric oxide (.N = O), a recently discovered biological mediator of vascular smooth muscle relaxation, is produced in increased amounts by numerous cell types exposed to a number of inflammatory cytokines.

PURPOSE

Our purpose was to determine if there is an increased production of .N = O in patients receiving IL-2 tumor immunotherapy, and, if so, whether increases in .N = O production correlate with hemodynamic instability.

METHODS

Twelve patients undergoing immunotherapy trials with IL-2 and anti-CD3 monoclonal antibody-activated lymphocytes (T-AK cells) were studied. Plasma levels of nitrate (NO3-), the stable end metabolic product of .N = O synthesis, were measured before and at the end of IL-2 treatment cycles.

RESULTS

We observed a ninefold increase in plasma levels of NO3- in patients after 7 days of treatment (P less than .0001). A significant decrease in both systolic and diastolic blood pressures was observed in all patients (P less than .001).

CONCLUSIONS

We propose that mediated induction of .N = O synthase enzyme leads to progressive increases in .N = O production which, in turn, produces clinically significant hypotension.

IMPLICATIONS

Since .N = O synthesis can be competitively inhibited by L-arginine analogues, a possible pharmacologic modulation of .N = O production could potentially contribute to better management of toxic side effects seen in IL-2 cancer therapies.

Anti-tumor vaccine adjuvant effects of IL-2 liposomes in mice immunized against MCA-102 sarcoma

MCA-102, a murine sarcoma previously reported to be non-immunogenic in C57/BL6 murine tumor models was used in a tumor vaccine preparation which included liposome encapsulated IL-2 as an adjuvant. C57/BL6 mice were immunized in the right hind footpad with irradiated MCA-102 murine sarcoma cells on days 0, 7, and 21 with or without IL-2 liposome adjuvant at 25,000 IL-2 units/injection. Mice were challenged with live tumor in the right flank on day 35. Survival of mice given IL-2 liposomes with irradiated MCA-102 cells was significantly prolonged over mice given tumor antigen with saline, and non-immunized mice. In addition, mice which received the IL-2 liposome adjuvant also had prolonged survival over those mice immunized with the additional control adjuvants of free IL-2 or dimyristoyl phosphatidyl choline (DMPC) lipid in the form of empty liposomes. IL-2 liposome plus tumor antigen also yielded a significant local protective response against live MCA-102 tumor challenge. When live tumor was injected into the site of previous immunizations on day 21 after two immunizations, the IL-2 liposome adjuvant group showed significantly delayed local growth of tumor compared to animals immunized without adjuvant, or with the adjuvants of empty liposomes or free IL-2. Finally, immunized mice were challenged with irradiated tumor cells and saline intradermally in the ears and delayed type hypersensitivity (DTH), an indicator of helper T cell response, was measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Proliferation and cytolytic function of anti-CD3 + interleukin-2 stimulated peripheral blood mononuclear cells following bone marrow transplantation

We evaluated the proliferation, cytolytic function, and phenotypic characteristics of anti-CD3 plus interleukin-2 (IL-2) stimulated peripheral blood mononuclear cells (PBMCs) from 44 patients with leukemia or non-Hodgkin's lymphoma (NHL) treated with multiagent chemotherapy or following bone marrow transplantation (BMT). BMT patients had decreased cell growth with only a 1.35 +/- 0.25 (autologous BMT for acute lymphoblastic leukemia [ALL]), 1.24 +/- 0.25 (autologous BMT for NHL), and 0.8 +/- 0.1 (allogeneic BMT for leukemia) mean fold increase by day 5 of culture compared with controls (4.0 +/- 0.4), P less than .001. Anti-CD3 + IL-2 activated cells from patients with ALL and NHL who had received autologous BMT and cells from patients with leukemia who underwent allogeneic BMT were more effective in lysing the natural killer (NK) sensitive target, K562, and the NK-resistant target, Daudi, compared with controls. In contrast, cytolysis of K562 and Daudi by cultured PBMCs from patients with ALL and NHL receiving multi-agent chemotherapy was similar to that of controls. Cultures from BMT recipients had a significant increase in CD16+ (autologous ALL 5.7 +/- 1.5%, P less than .01; autologous NHL 12.4 +/- 3.5%, P less than .001; allogeneic 14.3 +/- 2.9%, P less than .001) and CD56+ cells (autologous ALL 27.6 +/- 12.0%, P less than .01; autologous NHL 39.3 +/- 9.5%, P less than .001; allogeneic 42.7 +/- 7.4%, P less than .001) compared with controls (CD16+ 2.5 +/- 0.4%; CD56+ 6.9 +/- 0.9%). Stimulation of PBMCs with anti-CD3 + IL-2 is effective in generating cells with high cytolytic function post-BMT.

Generation of lymphokine-activated killer activity in T cells. Possible regulatory circuits

CD4+ and CD8+ T cells do not develop significant lymphokine-activated killer (LAK) activity when PBL are cultured with IL-2 or even when they are activated with a T cell stimulus such as OKT3 mAb. The possibility that a T cell regulatory mechanism prevents the development of LAK activity by CD4+ or CD8+ cells in OKT3 mAb and IL-2 cultures was tested by depleting CD8+ or CD4+ cells from PBL before stimulation with OKT3 and IL-2. Under these conditions, the remaining CD4+ and CD8+ cells were able to generate non-MHC-restricted lysis of NK-resistant tumor targets. Our data suggested that a regulatory signal was present in the culture to prevent the development of lytic function by T cells. T cells removed from the PBL cultures were, upon culture with IL-2, able to generate high LAK activity, suggesting that inhibition of the CD4+ or CD8+ T cell-mediated LAK activity was an active ongoing process, which blocked the lysis at the level of the activated cell and not the precursor cell. Mixing experiments demonstrated that the CD4+ or the CD8+ cells isolated from the PBL cultures were able to inhibit the development of lytic function in the CD4-depleted and CD8-depleted cultures. Transforming growth factor-beta (TGF-beta) has been shown to block LAK activity of NK cells in IL-2-stimulated cultures. When TGF-beta was added to CD4(+)- or CD8(+)-depleted cultures, it also inhibited LAK activity of T cells in a dose-dependent fashion, without interfering with T cell growth. Lytic activity returned to activated levels when TGF-beta was removed from the culture medium, thereby demonstrating the reversibility of TGF-beta inhibition.

Generation of lymphokine-activated killer activity in T cells. Possible regulatory circuits

CD4+ and CD8+ T cells do not develop significant lymphokine-activated killer (LAK) activity when PBL are cultured with IL-2 or even when they are activated with a T cell stimulus such as OKT3 mAb. The possibility that a T cell regulatory mechanism prevents the development of LAK activity by CD4+ or CD8+ cells in OKT3 mAb and IL-2 cultures was tested by depleting CD8+ or CD4+ cells from PBL before stimulation with OKT3 and IL-2. Under these conditions, the remaining CD4+ and CD8+ cells were able to generate non-MHC-restricted lysis of NK-resistant tumor targets. Our data suggested that a regulatory signal was present in the culture to prevent the development of lytic function by T cells. T cells removed from the PBL cultures were, upon culture with IL-2, able to generate high LAK activity, suggesting that inhibition of the CD4+ or CD8+ T cell-mediated LAK activity was an active ongoing process, which blocked the lysis at the level of the activated cell and not the precursor cell. Mixing experiments demonstrated that the CD4+ or the CD8+ cells isolated from the PBL cultures were able to inhibit the development of lytic function in the CD4-depleted and CD8-depleted cultures. Transforming growth factor-beta (TGF-beta) has been shown to block LAK activity of NK cells in IL-2-stimulated cultures. When TGF-beta was added to CD4(+)- or CD8(+)-depleted cultures, it also inhibited LAK activity of T cells in a dose-dependent fashion, without interfering with T cell growth. Lytic activity returned to activated levels when TGF-beta was removed from the culture medium, thereby demonstrating the reversibility of TGF-beta inhibition.

Regulation of lymphokine-activated killer activity and pore-forming protein gene expression in human peripheral blood CD8+ T lymphocytes. Inhibition by transforming growth factor-beta

The effect of transforming growth factor-beta 1 (TGF-beta) on activation-induced CD8+ T cell cytotoxicity and gene expression was investigated. TGF-beta was demonstrated to inhibit pore-forming protein (PFP) mRNA expression and total benzoyloxycarbonyl-L-lysine thiobenzyl ester esterase activity in CD8+ T cells cultured with IL-2 and OKT3 mAb for 6 to 18 days. Consistently, in the absence or presence of TGF-beta, the PFP mRNA expression and lymphokine-activated killer (LAK) activity of CD8+ T cells were closely correlated. The inhibitory effects of TGF-beta on both CD8+ T cell PFP mRNA expression and LAK activity were reversible by removal of TGF-beta from the culture. Expression of lymphokines, adhesion/recognition molecules, and activated p55 IL-2R, previously implicated in the lytic mechanism of cytotoxic lymphocytes, either was not detectable or did not correlate with TGF-beta inhibition of LAK activity. In addition, independently of effector/target cell binding, the lectin- or heteroconjugated antibody-dependent cellular cytotoxicity of IL-2/OKT3 mAb-activated CD8+ T cells was inhibited by preculture with TGF-beta. TGF-beta also inhibited the rapid activation-induced expression of PFP mRNA and cytotoxic potential in resting T cells, thereby indicating that the effect of TGF-beta was independent of T cell proliferation. TGF-beta inhibition of CD8+ T cell PFP mRNA expression and cytotoxic potential was TGF-beta dose dependent; however, a variety of activation stimuli (including IL-2, IL-6, and OKT3 mAb) were all similarly inhibited by TGF-beta. Therefore, TGF-beta may be an important general regulator of CD8+ T cell cytotoxic function, in particular by suppressing expression of PFP, a major cytolytic protein implicated in the lytic function of cytotoxic lymphocytes.

Regulation of lymphokine-activated killer activity and pore-forming protein gene expression in human peripheral blood CD8+ T lymphocytes. Inhibition by transforming growth factor-beta

The effect of transforming growth factor-beta 1 (TGF-beta) on activation-induced CD8+ T cell cytotoxicity and gene expression was investigated. TGF-beta was demonstrated to inhibit pore-forming protein (PFP) mRNA expression and total benzoyloxycarbonyl-L-lysine thiobenzyl ester esterase activity in CD8+ T cells cultured with IL-2 and OKT3 mAb for 6 to 18 days. Consistently, in the absence or presence of TGF-beta, the PFP mRNA expression and lymphokine-activated killer (LAK) activity of CD8+ T cells were closely correlated. The inhibitory effects of TGF-beta on both CD8+ T cell PFP mRNA expression and LAK activity were reversible by removal of TGF-beta from the culture. Expression of lymphokines, adhesion/recognition molecules, and activated p55 IL-2R, previously implicated in the lytic mechanism of cytotoxic lymphocytes, either was not detectable or did not correlate with TGF-beta inhibition of LAK activity. In addition, independently of effector/target cell binding, the lectin- or heteroconjugated antibody-dependent cellular cytotoxicity of IL-2/OKT3 mAb-activated CD8+ T cells was inhibited by preculture with TGF-beta. TGF-beta also inhibited the rapid activation-induced expression of PFP mRNA and cytotoxic potential in resting T cells, thereby indicating that the effect of TGF-beta was independent of T cell proliferation. TGF-beta inhibition of CD8+ T cell PFP mRNA expression and cytotoxic potential was TGF-beta dose dependent; however, a variety of activation stimuli (including IL-2, IL-6, and OKT3 mAb) were all similarly inhibited by TGF-beta. Therefore, TGF-beta may be an important general regulator of CD8+ T cell cytotoxic function, in particular by suppressing expression of PFP, a major cytolytic protein implicated in the lytic function of cytotoxic lymphocytes.

Antitumor effects of interleukin 2 liposomes and anti-CD3-stimulated T-cells against murine MCA-38 hepatic metastasis

The stimulation of murine splenocytes with the monoclonal antibody anti-CD3 and interleukin 2 (IL-2) results in the propagation of large numbers of cells (T-activated killer; T-AK) which demonstrate high therapeutic efficacy when infused with IL-2 into mice bearing pulmonary metastases. Interleukin 2 infusions are required to maintain the function of the adoptively transferred cells. Recent data demonstrate that the therapeutic efficacy can be enhanced by encapsulating IL-2 in liposomes. The present work tested the combination of T-AK cells with IL-2 liposomes in an immunotherapy model utilizing the MCA-38 murine colon adenocarcinoma. Expansion of murine splenocytes was achieved with anti-CD3 monoclonal antibody plus IL-2 and was consistently greater than 50-fold during a 9-day culture period. Cytolytic activity of the murine T-AK cells was mediated primarily by Lyt-2+ cells. In vivo results demonstrate synergistic therapeutic efficacy of the combination of IL-2 liposomes and T-AK cells. Evaluation of the in vivo distribution of these T-AK cells utilizing congenic mice demonstrates that Lyt-2+ cells from these in vitro cultures infiltrate hepatic metastases in vivo. The activation of lymphocytes with anti-CD3 monoclonal antibody and IL-2 appears to be a reproducible and convenient method of producing cells capable of producing antitumor effects in models of adoptive immunotherapy.

Importance in timing of cyclophosphamide on the enhancement of interleukin-2-induced cytolysis

We investigated the in vivo effects of cyclophosphamide (CY) on interleukin-2(IL-2)-induced cytolytic function and spleen cell immunophenotype. Pretreatment of A/J mice with CY (25 mg/kg or 75 mg/kg) i.p. on days -10 and -15 followed by IL-2 (50,000 U i.p. on days 0 to +3) resulted in increased lysis of YAC-1 target cells compared to the group receiving IL-2 without previous CY therapy. In contrast, when CY was given on day -5, the cytotoxicity against YAC-1 was not enhanced. Phenotypic analysis of splenocytes obtained from mice treated with CY on day -10 or -15 revealed a relative decrease in L3T4- and Lyt2-positive T cells. In vivo depletion of natural killer (NK) cells by anti-asialoGM1, prior to IL-2 therapy, abrogated the enhancing effect of CY on cytolysis while in vivo elimination of T cells by anti-L3T4 and anti-Lyt2 monoclonal antibodies did not, indicating that in the absence of T cell antigenic challenge, the increased cytolytic function after CY administration is probably mediated through NK cells. These findings provide evidence that CY may be used more effectively in IL-2-based immunotherapy protocols, if consideration is given to timing of CY and IL-2 administration.

Increased local antitumor effects of interleukin 2 liposomes in mice with MCA-106 sarcoma pulmonary metastases

The effects of liposome formulations of interleukin 2 (IL-2) and local route were studied in C57BL/6 mice with MCA-106 sarcoma pulmonary metastases. IL-2 liposomes made by hydration of powdered dimyristoyl-phosphatidylcholine with aqueous recombinant IL-2 had 95% of the IL-2 associated with the lipid fraction. When mice with pulmonary micrometastases were treated once daily with free cytokine on days 5, 6, and 7 after tumor inoculation, the intrathoracic route was superior to the i.p. or s.c. routes. When IL-2 liposomes were administered by the local intrathoracic route, significantly better antitumor effects (P less than 0.01) were seen compared to empty liposomes or free IL-2 as determined by (a) increased survival and (b) reduced numbers of pulmonary metastases. Minimal toxicity was observed. Results indicate that local route and incorporation of IL-2 in liposomes may enhance therapeutic efficacy and facilitate more practical daily dosing regimens.

Mature T-lineage leukemia with growth factor-induced multilineage differentiation

We report an acute T-lymphoblastic leukemia with a predominantly mature CD3+ CD7+ WT31+ phenotype that was induced to differentiate into different cell lineages by various recombinant human growth factors. In the presence of IL-3 or GM-CSF, the leukemic cells gave rise to myeloid and monocytic cells including terminally differentiated, partially functional, segmented neutrophilic granulocytes as assessed by morphologic, cytochemical, immunophenotypic, and functional criteria. In the presence of IL-2, leukemic granulated lymphoid cells exhibiting MHC-unrestricted cytotoxicity and expressing a CD2+ CD3+ CD5+ CD7+ CD8+ CD33+ WT31+ Leu19+ phenotype arose. Leukemic cell cultures initiated with IL-3 yielded growth factor-independent cells with a mixed lineage phenotype and morphologic and cytochemical evidence of immature blasts. These were T lymphocyte and myeloid surface antigen (CD2,CD3,CD5,CD7,CD13,CD33,WT31) positive. Identical rearrangements of the constant region of the TCR-delta gene and of the joining regions of the TCR-beta, -gamma, and -delta genes were observed in the fresh and all cultured leukemic cells, indicating that they were derived from the same malignant clone. Consistent with the molecular genetic data, the cytogenetic analyses of the GM-CSF-, IL-3-cultured and the growth factor-independent leukemic cells showed the presence of multiple, closely related abnormal clones, all of which had an interstitial deletion of part of the long arm of chromosome 6 and a complex 1;10;12 translocation. In conclusion, these data demonstrate the involvement of a multipotent leukemic precursor cell in this predominantly mature CD2+ CD3+ CD5+ CD7+ WT31+ T-ALL. This multipotent leukemic precursor may be susceptible to various growth factors and respond with ordered differentiation and maturation.

Anti-CD3 + IL-2-stimulated murine killer cells. In vitro generation and in vivo antitumor activity

The growth, phenotype, in vitro cytolytic characteristics, and in vivo antitumor activity of murine splenocytes stimulated with anti-murine CD3 mAb in combination with IL-2 as compared with IL-2 alone was investigated. When cultured for 12 days with anti-CD3 mAb + IL-2, murine splenocytes increased 100- to 4000-fold in number compared with only 6- to 20-fold for cultures stimulated with IL-2 alone. Anti-CD3 mAb + IL-2 activated cultures developed high lymphokine-activated killer activity against NK-resistant targets including the P815 mastocytoma cell line and fresh MCA 106 sarcoma. Peak cytotoxicity on a per cell basis developed by day 8 after anti-CD3 mAb + IL-2 activation. A large proportion of the total cytolytic activity of long term anti-CD3 mAb + IL-2-stimulated cultures was related to the presence of anti-CD3 in the assay, indicating enhancement of cytotoxicity by activated CD3+ T cells. Phenotypic analysis indicated that anti-CD3 mAb + IL-2-stimulated cultures contained heterogeneous populations of T cells with increased percentages of both CD4+ and CD8+ phenotypes compared with cultures stimulated with IL-2 alone. Anti-CD3 mAb + IL-2-stimulated cells were tested for their in vivo antitumor activity by using C57BL/6 mice bearing MCA 106 sarcoma pulmonary metastases. IL-2-activated murine killer cells were given in combination with in vivo IL-2 and indomethacin, the latter of which was shown to potentiate the antitumor effect of IL-2. When given on day 5 after tumor inoculation, cell doses as low as 5 x 10(6) anti-CD3 mAb + IL-2-stimulated cells per mouse significantly reduced the number of pulmonary metastases (p less than 0.005). Thus, activation with the combination of anti-CD3 mAb + IL-2 produces rapidly expanding cultures of cytolytic cells with demonstrated in vivo antitumor efficacy.

Lymphokine-activated killer activity in long-term cultures with anti-CD3 plus interleukin 2: identification and isolation of effector subsets

Peripheral blood lymphocytes cultured in recombinant interleukin 2 during 3 to 5 days (short-term cultures) develop the ability to lyse natural killer-resistant tumor lines and fresh tumor cells, i.e., express lymphokine-activated killer (LAK) function. Phenotypic analysis has shown these cells to be natural killer cells, i.e., CD16+ and/or Leu 19+ cells. CD3+,CD16- T-cells, instead, develop very low LAK function in these cultures. We recently reported the development of long-term (up to 21 days) cultured cells with LAK activity by stimulation with OKT3 + interleukin 2(IL2). These culture conditions repeatedly resulted in a several hundred-fold expansion in cell number. Specific LAK activity on Day 14 of culture was comparable to that of 3-day LAK cultures and could be further enhanced by the addition of interleukin 1 beta, beta-, or gamma-interferon. Total LAK activity was greatly increased in OKT3 + IL2 cultures over that found in short-term cultures. Isolation of effectors mediating LAK function in long-term cultures stimulated with OKT3 + IL2 showed that both CD3+,CD16- cells and CD16+,CD3- cells tested on Day 14 of culture expressed equivalent levels of LAK activity as shown by lysis of natural killer-resistant targets, HL60 and Daudi. Further dissection of the subpopulations developing LAK activity demonstrated that, in addition to CD16+,CD3- cells, CD3+, CD4-,CD8- cells and Leu 19+,CD3-,CD16- cells also developed high LAK activity in long-term cultures with OKT3 + IL2. Further, long-term culture with OKT3 + IL2 induced increases in the numbers not only of CD3+,CD4-,CD8- cells but also of CD16+,CD3- and Leu 19+,CD3-,CD16- cells. Although there is a significant increase in the number of CD3+,CD8+ cells, neither these, nor the CD3+,CD4+ cells, mediate LAK activity to the same extent as the populations mentioned above.

Anti-CD3 + IL-2-stimulated murine killer cells. In vitro generation and in vivo antitumor activity

The growth, phenotype, in vitro cytolytic characteristics, and in vivo antitumor activity of murine splenocytes stimulated with anti-murine CD3 mAb in combination with IL-2 as compared with IL-2 alone was investigated. When cultured for 12 days with anti-CD3 mAb + IL-2, murine splenocytes increased 100- to 4000-fold in number compared with only 6- to 20-fold for cultures stimulated with IL-2 alone. Anti-CD3 mAb + IL-2 activated cultures developed high lymphokine-activated killer activity against NK-resistant targets including the P815 mastocytoma cell line and fresh MCA 106 sarcoma. Peak cytotoxicity on a per cell basis developed by day 8 after anti-CD3 mAb + IL-2 activation. A large proportion of the total cytolytic activity of long term anti-CD3 mAb + IL-2-stimulated cultures was related to the presence of anti-CD3 in the assay, indicating enhancement of cytotoxicity by activated CD3+ T cells. Phenotypic analysis indicated that anti-CD3 mAb + IL-2-stimulated cultures contained heterogeneous populations of T cells with increased percentages of both CD4+ and CD8+ phenotypes compared with cultures stimulated with IL-2 alone. Anti-CD3 mAb + IL-2-stimulated cells were tested for their in vivo antitumor activity by using C57BL/6 mice bearing MCA 106 sarcoma pulmonary metastases. IL-2-activated murine killer cells were given in combination with in vivo IL-2 and indomethacin, the latter of which was shown to potentiate the antitumor effect of IL-2. When given on day 5 after tumor inoculation, cell doses as low as 5 x 10(6) anti-CD3 mAb + IL-2-stimulated cells per mouse significantly reduced the number of pulmonary metastases (p less than 0.005). Thus, activation with the combination of anti-CD3 mAb + IL-2 produces rapidly expanding cultures of cytolytic cells with demonstrated in vivo antitumor efficacy.

Continuous infusion of recombinant interleukin-2 and lymphokine-activated killer cells in refractory malignancies

Adoptive immunotherapy with recombinant interleukin-2 (rIL-2) and lymphokine-activated killer (LAK) cells has been reported to effect the regression of tumor in patients with a variety of malignancies. Responses have occurred in patients treated with high-dose bolus rIL2 as well as lower-dose continuous intravenous infusion. Ten patients who had been extensively pretreated with systemic chemotherapy with or without additional radiation therapy were treated with continuous infusion rIL2 and LAK cells. Five patients received rIL2 alone for 96-120 hours prior to leukapheresis in addition to rIL2 at the time of LAK cell infusion. Three patients received LAK cells that had been cultured for 14 days in an automated tissue culture system. No responses were seen in this ten-patient cohort. While the lack of response in these patients may be related to any one or more of several variables, patients who have been heavily pretreated may not respond as well as patients who have received little to no systemic chemotherapy.

Mechanism of cultured endothelial injury induced by lymphokine-activated killer cells

A new form of therapy of experimental tumors, utilizing lymphokine-activated killer (LAK) cells and high doses of interleukin 2, has recently been applied in the treatment of human neoplasms. Severe side effects, suggestive of a diffuse vascular injury of unknown etiology, have prevented a more widespread application of this form of therapy. We have investigated the etiology of this clinical capillary leak syndrome, using an in vitro model of endothelial injury. LAK cells, but not interleukin 2 itself, are cytotoxic to cultured human endothelial cells, and this cytotoxicity is time and dose dependent. This human endothelial cell cytotoxicity can be inhibited by depletion of extracellular Ca2+, inhibition of the effector cell microtubular system, and inhibitors of serine proteases, but is not inhibited in the presence of toxic oxygen radical scavengers. LAK cell-mediated endothelial cytotoxicity is far more potent than that exhibited by maximally stimulated polymorphonucleocytes. LAK cell-mediated injury of human endothelium may possibly be responsible for the capillary leak syndrome observed in patients treated with high doses of interleukin 2 and LAK cells.

Augmentation of cell number and LAK activity in peripheral blood mononuclear cells activated with anti-CD3 and interleukin-2. Preliminary results in children with acute lymphocytic leukemia and neuroblastoma

A wide variety of human cancers currently have no effective treatment and are potential targets for lymphokine-activated killer (LAK) cellular immunotherapy. Relapsed acute lymphocytic leukemia (ALL) and neuroblastoma are two of the major therapeutic challenges in pediatric oncology today. However, one problem which makes LAK immunotherapy in children particularly difficult is obtaining the large numbers of cells required. Present adult therapeutic LAK protocols have utilized short-term (5 day) cultures of interleukin-2 (IL2)-activated cells which are initially obtained from leukopheresis. Since routine use of this procedure in small children is not practical, we have investigated a different approach to obtain increased cell numbers by activation of peripheral blood mononuclear cells with OKT3, a mitogenic anti-CD3 monoclonal antibody, and IL2. Cell growth and LAK activity in OKT3 + IL2-activated cultures were compared to cultures activated with IL2 alone in 2 children with relapsed ALL and 2 children with stage IV neuroblastoma. OKT3 + IL2-activated cultures had marked increases in cell number: after 14 days the OKT3 + IL2-activated cultures yielded an approximately 500-fold increase in cell number compared to a 7-fold increase for cultures activated with IL2 alone. In vitro 51Cr release assays were used to estimate LAK activity of the cultures at 7 and 14 days. When tested against HL60, a natural killer (NK)-resistant tumor cell line, not only were total cytolytic units greatly increased in OKT3 + IL2-stimulated cultures by lytic activity on a per cell basis (lytic units/1 x 10(6) cells) had also markedly increased on day 14 of culture. Phenotypic analysis demonstrated that 80% to 90% of cells in OKT3 + IL2-stimulated cultures were CD3 + T cells. Variable low percentages of CD16 + NK cells were seen in these cultures. In summary, OKT3 + IL2 activation resulted in a large increase in cell yield and the development of high level LAK activity using peripheral blood mononuclear cells from children with cancer. This approach may facilitate the utilization of increased cell numbers in future adoptive immunotherapy protocols, especially in pediatric patients.

Long-term growth of lymphokine-activated killer (LAK) cells: role of anti-CD3, beta-IL 1, interferon-gamma and -beta

Peripheral blood lymphocytes (PBL) cultured in interleukin 2 (IL 2)-containing medium in conventional tissue culture develop the ability to lyse fresh tumor cells; such cells are referred to as lymphokine-activated killer (LAK) cells. LAK activity peaks by day 5 of culture and declines rapidly thereafter. We studied culture conditions and signals that allow for long-term culture and expansion of cells with LAK activity. By culturing cells at relatively low densities and regularly replenishing medium and recombinant IL 2 (r-IL 2), LAK function is significantly higher as compared with short-term cultures, and remains present for at least 21 days while cell numbers undergo an average 100-fold expansion. By activating these cultures with anti-CD3 (OKT3) monoclonal antibody and r-IL 2, an approximately 1000-fold expansion in the cell number is obtained with maintenance of comparable levels of LAK activity. The exogenous addition of beta interleukin 1 (beta-IL 1), interferon-beta (IFN-beta) or interferon-gamma (IFN-gamma) can augment the lytic activity of cell populations expanded by anti-CD3 plus r-IL 2. These approaches may enable the in vitro generation from individual donors of much greater numbers of LAK cells for adoptive immunotherapy than can now be obtained with the 3 to 5 day in vitro culture systems.

Long-term growth of lymphokine-activated killer (LAK) cells: role of anti-CD3, beta-IL 1, interferon-gamma and -beta

Peripheral blood lymphocytes (PBL) cultured in interleukin 2 (IL 2)-containing medium in conventional tissue culture develop the ability to lyse fresh tumor cells; such cells are referred to as lymphokine-activated killer (LAK) cells. LAK activity peaks by day 5 of culture and declines rapidly thereafter. We studied culture conditions and signals that allow for long-term culture and expansion of cells with LAK activity. By culturing cells at relatively low densities and regularly replenishing medium and recombinant IL 2 (r-IL 2), LAK function is significantly higher as compared with short-term cultures, and remains present for at least 21 days while cell numbers undergo an average 100-fold expansion. By activating these cultures with anti-CD3 (OKT3) monoclonal antibody and r-IL 2, an approximately 1000-fold expansion in the cell number is obtained with maintenance of comparable levels of LAK activity. The exogenous addition of beta interleukin 1 (beta-IL 1), interferon-beta (IFN-beta) or interferon-gamma (IFN-gamma) can augment the lytic activity of cell populations expanded by anti-CD3 plus r-IL 2. These approaches may enable the in vitro generation from individual donors of much greater numbers of LAK cells for adoptive immunotherapy than can now be obtained with the 3 to 5 day in vitro culture systems.

Cytotoxic T lymphocytes: blocked differentiation at the 'poised' stage

The effect of different concentrations of phorbol myristate acetate (PMA) on the development of cytotoxic cells was studied. PMA was selectively able to prevent the development of cytotoxic cells in a mixed leucocyte culture, while allowing the responding cells to proliferate. The higher concentration of PMA (10(-5)M) blocked both direct cytotoxicity and lytic activity in the presence of lectin, while the lower concentration (10(-8) M) only prevented direct lytic function. The removal of PMA and subsequent addition of recombinant interleukin 2 (IL-2) or IL-2-containing supernatants effectively reversed the effect of PMA with recovery of antigen-specific lytic function of cells treated with 10(-8) M, while cells treated with 10(-5)M PMA only recovered lectin-dependent cytotoxic ability.

Loss and re-acquisition of lytic function by cloned cytotoxic T lymphocytes: role of specific antigen and interleukin 2

We have previously reported the isolation of 2 human allospecific cytotoxic T-lymphocyte (CTL) clones that can undergo a reversible functional change from a highly lytic phase to a nonlytic quiescent phase and again to a lytic phase. The entire process was found to be regulated by recombinant interleukin 2 (rIL-2). We have now extended these studies in 3 ways. First, we show that specific alloantigens can also function as a signal to reactivate lytic function in the reverted CTL. However, in contrast to CTL reactivated with rIL-2, the antigen-reactivated CTL apparently fail to undergo subsequent cell division. Second, we have also found that this reversion phenomenon is not the same for all CTL tested, as 2 other CTL clones were found that did not revert to the non-lytic phase when cultured for up to 60 h in rIL-2-free medium. Third, the expression of Tac (IL-2 receptor) was also studied throughout the process of reversion and reactivation. rIL-2 added to the cell that had reverted to a non-lytic phase induced, an increase in the expression of Tac receptors during the reactivation phase, to levels greater than those expressed on cells continuously cultured in rIL-2-supplemented medium.