Protein A Potentiates Lymphokine-Activated Killer Cell Induction in Normal and Melanoma Patient Lymphocytes

The effects of purified protein A from Staphylococcus aureus Cowan I strain on induction of lymphokine (IL-2) activated killer (LAK) activity were studied in normal as well as melanoma patient's lymphocyte. The coculture of peripheral blood mononuclear cells (PBMC) with various doses of protein A (0.001, 0.01 and 0.1 μmlg/ml) and IL-2 (100 U/ml) for 4 days produced synergistic effect on the LAK cells mediated cytotoxicity. The potentiation of cytotoxicity and lytic ability of LAK cells against NK sensitive (K-562) and NK-resistant (M1 4) tumor cells were observed. Further there was potentiation of DNA synthesis in PBMC after 4 days culture. Similar results were found when PBMC from melanoma patients were cultured with PA and IL-2. The potentiation of LAK cell induction associated with its cytotoxic and lytic potential by low doses of IL-2/PA regiment may be helpful in the development of LAK immunotherapy of the cancer patients.     

Effect of ASTA-Z 7575 (INN Maphosphamide) on Human Lymphokine-Activated Killer Cell Induction

Recent studies combining chemotherapeutic agents with various biological response modifiers for the treatment of cancer have shown promising results. Cyclophosphamide (Cy) is the most widely used alkylating agent and a major constituent of combination chemotherapy regimens for many neoplastic diseases. It has been reported that Cy is a cytotoxic drug, which becomes immunosuppressive at higher doses. A synthetic metabolite of Cy, ASTA-Z, has recently been produced. ASTA-Z is more active and stable by itself and does not need to be metabolically converted to an active compound. the combined effect of Cy and interleukin-2 (IL-2) on the induction of lymphokine-activated killer (LAK) cells is not known. Therefore, we decided to investigate the effect of ASTA-Z on the induction and function of LAK. the coculture of peripheral blood mononuclear cells (PBMC) with various concentrations of ASTA-Z (0, 10^-6 10^-5, 10^-4 and 10^-3 dilution) and IL-2 (50 U/ml) for 4 days produced significant suppression of cytotoxicity and lytic ability of the LAK cells against NK-sensitive (K562) and NK-resistant (M14) tumor cell lines. the lower doses of ASTA-Z did not affect the generation of LAK cells, its cytotoxicity and lytic ability of ASTA-Z against both NK-sensitive and NK-resistant tumor cell lines. Furthermore, the ASTA-Z produced dose-dependent suppression of the proliferative response of LAK cells. the significant therapeutic benefit in the cancer patient may be achieved by the low dose regimen of Cy and IL-2 because it has no deleterious effect on the induction and function of LAK cells.     

Effect of ASTA-Z 7575 (INN Maphosphamide) on Human Lymphokine-Activated Killer Cell Induction

Abstract

Recent studies combining chemotherapeutic agents with various biological response modifiers for the treatment of cancer have shown promising results. Cyclophosphamide (Cy) is the most widely used alkylating agent and a major constituent of combination chemotherapy regimens for many neoplastic diseases. It has been reported that Cy is a cytotoxic drug, which becomes immunosuppressive at higher doses. A synthetic metabolite of Cy, ASTA-Z, has recently been produced. ASTA-Z is more active and stable by itself and does not need to be metabolically converted to an active compound. the combined effect of Cy and interleukin-2 (IL-2) on the induction of lymphokine-activated killer (LAK) cells is not known. Therefore, we decided to investigate the effect of ASTA-Z on the induction and function of LAK. the coculture of peripheral blood mononuclear cells (PBMC) with various concentrations of ASTA-Z (0, 10^?6 10^?5, 10^?4 and 10^?3 dilution) and IL-2 (50 U/ml) for 4 days produced significant suppression of cytotoxicity and lytic ability of the LAK cells against NK-sensitive (K562) and NK-resistant (M14) tumor cell lines. the lower doses of ASTA-Z did not affect the generation of LAK cells, its cytotoxicity and lytic ability of ASTA-Z against both NK-sensitive and NK-resistant tumor cell lines. Furthermore, the ASTA-Z produced dose-dependent suppression of the proliferative response of LAK cells. the significant therapeutic benefit in the cancer patient may be achieved by the low dose regimen of Cy and IL-2 because it has no deleterious effect on the induction and function of LAK cells.     

Impaired T and NK cell response of bone marrow and peripheral blood stem cell products to interleukin (IL)-2.

The function of steady-state and interleukin (IL)-2-co-cultured mononuclear cells differs significantly between bone marrow (BM) products, growth factor-mobilized peripheral blood stem cell (PSC) products and normal peripheral blood mononuclear cells (PBMC). The natural killer (NK) cell activity and T cell proliferative response of PSC products from non-Hodgkin's lymphoma (NHL) patients are significantly higher than that of BM products and similar to normal PBMC. However, following a five-day co-culture with IL-2 (100 IU/ml), the NK activity of PSC, PBMC, and BM products (lytic units) was increased 176-, 40-, and 14-fold, respectively, compared to that observed prior to IL-2 culture. In contrast, lymphokine activated killer (LAK) cytotoxicity prior to IL-2 culture was low in PSC and BM products and normal PBMC, but was significantly increased in PSC products and PBMC following IL-2 co-culture. The proliferative response of PSC and BM products to the T cell mitogen phytohemagglutinin (PHA) was significantly lower than that observed with normal PBMC; however, PSC had a significantly higher response than cells from BM products. Similar patterns of T cell PHA mitogenic response were observed after IL-2 co-culture. In addition, the IL-2 mitogenic responses of IL-2-co-cultured PSC and BM products were also significantly lower than that observed with PBMC co-cultured with IL-2. The IL-2 mitogenic response of PBMC was also significantly increased compared to prior to IL-2 co-culture; whereas, the IL-2 mitogenic responses from PSC and BM cells were not. In summary, co-culture with IL-2 can increase the NK and LAK cell cytotoxicity of PSC and BM products from NHL patients, but IL-2 co-culture does not improve T cell function within either BM or PSC products.     

人白细胞介素4诱导杀伤细胞的研究

人重组白细胞介素４（ｒｈＩＬ－４）在ＰＨＡ协同下，从人外周血单核细胞（ＰＢＭＣ）诱导出明显的ＬＡＫ活性，其对Ｋ５６２、Ｒａｊｉ细胞的杀伤力低于ＩＬ－２诱导者，对ＴＢＬ－Ｅ，ＰＨＡ活化的淋巴母细胞（ＰＨＡ－ｂｌａｓｔｓ）的杀伤力和ＩＬ－２诱导者相似。在ＰＨＡ介导的４小时５１Ｃｒ杀伤试验中，加入ＰＨＡ后，ＩＬ－４－ＬＡＫ对ＰＨＡ－ｂｌａｓｔｓ的杀伤力提高２．３倍，而ＩＬ－２－ＬＡＫ对ＰＨＡ－ｂｌａｓｔｓ的杀伤力无变化，提示ＩＬ－４主要诱导ＣＴＬ样活性，而ＩＬ－２主要诱导ＮＫ样活性，ＩＬ－４诱导效应ＣＴＬ的能力强于ＩＬ－２。我们的实验同时证实，在淋巴细胞活化的早期，ＩＬ－４抑制ＩＬ－２诱导的ＬＡＫ活性，淋巴细胞活化后，ＩＬ－４与ＩＬ－２有协同作用，增强ＩＬ－２诱导的ＬＡＫ活性。     

丝裂霉素C对人胎脾LAK细胞活性的影响

本文对人胎脾LAK细胞活性及丝裂霉素C(MMC)对LAK活性的影响作了初步研究。结果显示,人胎脾淋巴细胞可诱导产生明显的LAK活性,对K562和Raji瘤细胞的杀伤活性分别为74.4％和69.4％(E:T=50:1)。诱生的LAK细胞经不同浓度MMC处理后,DNA合成受到显著抑制(p<0.O1),但仍可保持较高水平的LAK活性。提示细胞增殖对MMC的抑制作用更为敏感,LAK细胞在效应阶段并非绝对有赖于细胞增殖。     

Evidence that interleukin-4 suppression of lymphokine-activated killer cell induction is mediated through monocytes.

Recombinant human interleukin-4 (IL-4) and transforming growth factor-beta (TGF-beta) reduce recombinant interleukin-2 (IL-2) induction of lymphokine-activated killer (LAK) cell activity from human peripheral blood mononuclear cells (PBMC). Monocytes can be removed from PBMC by adherence, leaving a peripheral blood lymphocyte population (PBL) which also responds to IL-2 to generate LAK activity. PBL generation of LAK cytotoxicity is susceptible to inhibition by TGF-beta, but not by IL-4. Readdition of purified monocytes to PBL is accompanied by return of the suppressive action of IL-4 on the generation of LAK activity. Induction of LAK cytolysis from Percoll-isolated T cells (greater than 90% CD3+) is also refractory to the inhibitory effect of IL-4. When PBMC were cultured in IL-2, with and without IL-4, subsequent sorting of CD3+ and CD3- lymphocytes by flow cytometry demonstrated that IL-4 had suppressed LAK induction in both effector populations. This suggests that, although isolated CD3+ cells are not susceptible to IL-4 suppression of IL-2 activation, they are sensitive to inhibition when part of a mixed PBMC population. Evidence is presented for the first time that this suppression is mediated via the action of IL-4 on monocytes.     

Long-term cultures of human peripheral blood lymphocytes with recombinant human interleukin-2 generate a population of virtually pure CD3+ CD16- CD56- large granular lymphocyte LAK cells.

It has been reported that lymphocytes from peripheral blood (PBL) cultured with interleukin-2 (IL-2) produce predominantly CD16+ lymphokine-activated killer (LAK) cells. We developed a two-step method to generate LAK cells from human PBL in long-term cultures (10-12 days) with recombinant human IL-2 (rhIL-2) and characterized the evolving LAK cell population by testing its phenotype and cytotoxic activity as a function of time. The starting PBL displayed some natural killer (NK) cytotoxicity but no LAK activity. At day 6, the cells were a mixed population of about 80% CD3+ and 6% CD16+ cells. Little proliferation was evident but strong LAK activity was detected. After 10-12 days, major cell expansion had occurred and they were essentially a pure (greater than 90%) CD3+ CD16- CD56- cell population large granular lymphocyte (LGL) by morphology that displayed strong non-MHC-restricted killing activity (greater than 200 lytic units). Over the same period of time, the CD16+ cells had almost completely regressed in these cultures. This preferential induction of CD+ LAK cells was not an effect of IL-2 concentration as 10 U/ml was as effective as 500 U/ml. Further characterization revealed a major population of CD4+ (60%) and CD8+ (30%) with a smaller fraction (less than 9%) of gamma delta + cells. These results indicate that a virtually pure CD3+ LAK cells population was produced with long-term cultures of lymphocytes from peripheral blood in rhIL-2, in which active proliferation of the CD3+ but not CD16+ cells occurred.     

Reduced LAK cytotoxicity of peripheral blood mononuclear cells in patients with bladder cancer: Decreased LAK cytotoxicity caused by a low incidence of CD56+ and CD57+ mononuclear blood cells

The cytotoxicity of unstimulated peripheral blood mononuclear cells (US-PBMC), phytohemagglutinin (PHA)-stimulated PBMC (PS-PBMC) and interleukin-2 (IL-2)-activated PBMC (LAK cells) was assessed in patients with noninvasive and invasive transitional-cell bladder cancer and compared with those determined in healthy controls. The differences in the cytotoxicities were correlated with specific changes in the subsets of peripheral blood mononuclear cells (PBMC). PBMC from 37 patients and 13 healthy controls were tested against the bladder cancer cell line T24 in⁵¹Cr-release assays. The PBMC subsets were analyzed using monoclonal antibodies against T cells, natural killer (NK) -cells, monocytes, and activation markers. The cytotoxicities of US-PBMC, PS-PBMC, and LAK cells were all significantly lower in the cancer patients than in the controls (P<0.05). The percentages of PBMC positive for the NK-cell markers CD56 and CD57 were lowest in the patients and were correlated to the decrease in cytotoxicity. Depletion of CD56⁺ or CD57⁺ cells from PBMC prior to or after 2 days stimulation with IL-2 demonstrated that these cells are the major source of LAK-cell cytotoxicity and showed that the reduced ability of bladder cancer patient PBMC to develop LAK-cell cytotoxicity is a result of a low incidence of CD56⁺ and CD57⁺ cells in the blood. These findings indicate that IL-2 therapy alone might not be a sufficient therapy of bladder cancer patients.     

Age-associated decline in IL-2 and IL-12 induction of LAK cell activity of human PBMC samples

Previously we reported that young and elderly natural killer (NK) cell activity against the standard NK sensitive K562 cell line can be augmented to the same degree by IL-2 and IFN-. We have extended these studies to include IL-12. Similar to IL-2 and IFN-, IL-12 can enhance NK cytotoxicity to the same degree in both young and elderly samples over a wide range of doses and incubation times when K562 cells are used as targets. However, in contrast to our findings with the NK system, we have observed that induction of lymphokine activated killer (LAK) cell activity, as defined by the ability of peripheral blood mononuclear cells (PBMC) samples to lyse the normally NK resistant Daudi cell line, was significantly decreased in the elderly samples compared to young samples. Comparable age-associated differences were observed in LAK activity after induction with IL-2, IL-12, and IFN- at varying doses and incubation times. We hypothesize an age-associated deficiency either in the mechanism of LAK induction or in target cell recognition.     

Lymphokine-activated killer cytotoxicity against pancreas adenocarcinoma cell lines and vascular endothelial cells

Eight pancreas carcinoma cell lines of duct cell origin (PCI-6, 10, 19, 24, 35, 43, 55, and 64) were established. Using one of these lines, PCI-24, human umbilical vein endothelial cells (HUVEC), and several recombinant cytokines, conditions and specificity of antl-PCI LAK induction were Investigated, with the focus on a search for lymphokine-activated killer (LAK) activity that differentiates neoplastic (PCI) from non-neoplastic (HUVEC) cells. Interferon-γ (IFN-γ), IFN-α, IL-4, 11–6, and IL-7, but not tumor necrosis factor-α (TNF-α) or IL-1β, induced a weak LAK activity against PCI-24, whereas IL-2-induced (1000U/mL) LAK exhibited a far more potent cytotoxicity. When these cytokines were added at the suboptimal dose IL-2 (100U/mL), no significant augmentation in LAK activity was induced. Staphylococcal protein A (SpA) induced LAK activity as potent as that seen with IL-2 (1000 U/mL). Both IL-2-induced and SpA-induced LAK had a potent, dose-dependent cytotoxicity against HUVEC. HUVEC inhibited both IL-2– and SpA-induced LAK cytotoxicity against PCI-24 to almost the same extent as seen with PCI-24. Thus, two potent LAK-inducers did not generate LAK activity that differentiates neoplastic from non-neoplastic cells. Thus, in vitro cytotoxicity of LAK agalnst non-neoplastic endothelial cells is unavoidable when handling cytokines in LAK induction.     

Lymphokine-activated killer cell function of peripheral blood mononuclear cells, spleen cells and regional lymph node cells in gastric cancer patients.

Lymphokine-activated killer (LAK) cells generated by culture of peripheral blood mononuclear cells (PBMC), spleen cells (SPC) and regional lymph node cells (LNC) with IL-2 for 4 days were examined for their functional capabilities in 29 patients with gastric carcinoma. The cytotoxic activity of LAK cells induced from LNC was significantly lower than that from either PBMC or SPC, although there was no difference between PBMC or SPC. The induction of mRNA of interferon-gamma (IFN-gamma) or tumour necrosis factor-alpha (TNF-alpha) and the production of these cytokines in the non-adherent LAK cells from LNC were also significantly reduced compared with those from PBMC or SPC. Further, the LAK cells from LNC secreted significantly lower levels of these cytokines when stimulated with tumour target, Raji cells, although the production of these cytokines was markedly increased by stimulation with the targets in all three cell populations. Phenotypic analysis of each cell population revealed a decreased proportion of the cells mediating natural killer (NK) activity, including CD16+, CD56+, and CD57+ cells in LNC either before or after culture, although OKIa1+ and CD25+ cells were uniformly increased in all cell populations after culture. Changes in subpopulations of CD4+ and CD8+ cells in LNC were not apparently different from PBMC or SPC. These results indicated the differential reactivity of each lymphocyte population to IL-2 and the reduced LAK cell function of LNC compared with PBMC or SPC in patients with gastric carcinoma.     

The combined treatment of human peripheral blood mononuclear cells with thymolymphotropin and interleukin 2 increases PPD-driven T-cell proliferation and IL-2 induced cellular cytotoxicity against HIV-infected cells.

Two in vitro systems (the DNA synthetic response to mycobacterial antigens and cytotoxicity against lymphoid cells) were used to analyse the effect of thymolymphotropin (TLT) on peripheral blood mononuclear cells (PBMC). Purified protein derivative of mycobacteria (PPD)-driven T-cell proliferation in low-responder donors was increased by the combined treatment with TLT and suboptimal doses of recombinant interleukin 2 (IL-2). Similarly, the activities of natural killer (NK) cells and lymphokine-activated killer (LAK) cells have been enhanced in PBMC cultures pretreated with TLT. Also, TLT showed an enhancing effect on the development of LAK cells capable of lysing Epstein-Barr virus (EBV)-transformed B-lymphocytes infected or uninfected with the human immunodeficiency virus (HIV).     

Lymphokine activated killer (LAK) cells in antibody dependent cellular cytotoxicity (ADCC) using MAb 17-1A: a combination of potential usefulness in tumor therapy

Peripheral blood lymphocytes (PBL) stimulated by interleukin-2 (IL-2) for 48-96h, generated killer cells against the human colon cancer cell line SW948. The killing capacity increased significantly when the specific mouse monoclonal antibody (MAb) 17-1A was present during the lytic process. The chimeric antibody 17-1A determined a significantly stronger cytotoxicity compared to mouse MAb 17-1A. MAb BR55-2 which recognizes a different antigen on SW948 target cells mediated a similar cytotoxicity as MAb 17-1A. Presence of alpha-interferon (IFN) during the lytic assay significantly enhanced the killing of the tumor by lymphokine activated killer (LAK) cells as well as by LAK cells and mouse MAb 17-1A. However, when chimeric MAb 17-1A and LAK cells were used alpha-IFN failed to increase the lytic activity, probably due to already maximum lysis in the system. Combinations of various biological response modifiers such as monoclonal antibodies, IL-2/LAK cells and alpha-IFN carry great promise to improve this kind of therapy for cancer patients.     

Human recombinant IL-4 suppresses the induction of human IL-2 induced lymphokine activated killer (LAK) activity.

The effect of recombinant human interleukin 4 (rhIL-4) on the induction in vitro of human lymphokine activated killer cell (LAK) activity was investigated. Peripheral blood mononuclear cells (PBMC) from normal healthy donors were incubated for 4 days with or without recombinant human interleukin-2 (rhIL-2) in the presence or absence of rhIL-4. LAK activity was measured against the NK-resistant colon adenocarcinoma cell line SW742, and NK mediated cytotoxicity was determined using NK sensitive K562 cells. Unlike previous reports using mouse effector cells, rhIL-4 neither induced LAK activity nor augmented the cytotoxic response induced by rhIL-2. In four out of six experiments there was a significant reduction of rhIL-2 induced LAK in the presence of rhIL-4, accompanied by a reduction of Tac antigen expression by rhIL-2 activated cells. Recombinant hIL-4 failed to influence the effector phase of the activated PBMC against SW742 or K562 targets.     

Up-regulation of IL-2 induced lymphokine activated killer cell activity by cisplatin and FK-565: involvement of calcium ion.

As reported earlier, the IL-2 induced lymphokine activated killer (LAK) activity is significantly up-regulated in the presence of cisplatin/FK-565. Based on these observations, we have investigated whether calcium is involved in the generation of LAK activity by IL-2 alone or along with CP/FK-565. We have shown that treatment of PBMC with IL-2 for four days caused an increase in intracellular free calcium and in ATP levels, which were further significantly enhanced when LAK cells were generated in the presence of CP/FK-565. Depletion of calcium resulted in decreased cytotoxic activity. Addition of tumor cells to LAK cells, generated in the presence of IL-2 alone or along with CP/FK-565 caused an instant rise in intracellular free calcium which was significantly decreased when an increase in intracellular free calcium was observed in calcium-free, EGTA-containing buffer. These data suggest that calcium is required for the activation and manifestation of lytic activity by LAK cells. Further, we observed that the increase in intracellular free calcium is not associated with the blastogenic response of peripheral blood mononuclear cells in response to treatment of IL-2 alone or together with CP/FK-565.     

In vivo treatment with interferon causes augmentation of IL-2 induced lymphokine-activated killer cells in the organs of mice.

Interferon-alpha (IFN-alpha) has been shown to synergize with IL-2 in the regression of a variety of established murine tumours and studies are underway to explore this combination in patients with advanced cancers as well. To understand the mechanism of synergy we have studied lymphokine-activated killer (LAK) cell activity in various compartments of mice in response to IFN-alpha and IL-2 administration. The effects of IFN-gamma, TNF-alpha and IL-4 were also examined. C57BL/6 mice were injected intraperitoneally with HBSS, IL-2 alone, IFN-alpha alone or both, two times a day for 7 days. On days 4 and 8, LAK activity was tested in a 4-h chromium release in cells obtained from lungs, spleen, and liver using fresh MCA-102 tumour cells as targets. The cells from control mice failed to lyse the MCA-102 target. IL-2 caused the generation of LAK activity and an increase in total cell yield in all the organs after 3 days of injection. IFN-alpha failed to generate LAK activity but when administered along with IL-2, caused synergistic enhancement of LAK lysis of MCA-102 target cells. Cell yield in this group was lower as compared with the IL-2-treated group. LAK activity tested after 7 days of IL-2 therapy was significantly decreased compared with that observed after 3 days. However, activity remained at as high a level after 7 days of therapy as after 3 days of therapy in animals treated with IFN-alpha and IL-2. FACS analysis revealed that asialo GM-1+ (ASGM-1) and NK1.1+ cells were increased in number in IL-2 and IL-2 plus IFN-alpha-treated spleen; however, the number of these cells was similar in both groups. In the liver, ASGM-1+ cells were higher in the IL-2 plus IFN-alpha group than in the group treated with IL-2 alone. By in vitro depletion utilizing antibody and Rbc' experiments, it was clear that both ASGM-1+ and NK1.1+ cells from the spleen mediated most of the cytotoxicity of MCA-102 targets. Pre-treatment irradiation (5 Gy) of mice completely abrogated the capability of IL-2 or IL-2 plus IFN-alpha to generate LAK activity. IFN-gamma also had a stimulatory effect on IL-2 induction of LAK activity. Tumour necrosis factor-alpha (TNF-alpha) and IL-4 failed to generate LAK activity and, in combination with IL-2, no additional stimulatory effect was observed.(ABSTRACT TRUNCATED AT 400 WORDS)     

LAK-cell-mediated cytotoxicity against tumor cell targets used to monitor the stimulatory effect of interleukin-2: cytotoxicity, target recognition and phenotype of effector cells lysing the Daudi, T24 and K562 tumor cell lines.

The T24 transitional bladder carcinoma cell line, the Daudi Burkitt lymphoma cell line and the K562 erythroleukemia cell line have all been used as target cells in 51Cr release assays to measure the in vivo induced lymphokine-activated killer (LAK) cell cytotoxicity during interleukin-2 (IL-2) therapy of cancer patients. However, different relationships between the clinical response to IL-2 treatment and the LAK cytotoxicity have been reported using these three different target cells. The purpose of the present study was to evaluate whether the LAK cytotoxicities measured against these target cells represent similar effector-to-target-cell interactions, so similar conclusions may be drawn of 51Cr release assay results in which the cell lines are used as target cells. The cytotoxicity of peripheral blood mononuclear cells (PBMC) and PBMC depleted of different natural killer and T cell subsets was measured against the three targets. LAK cell recognition of targets was evaluated by cold target inhibition experiments, and the development of LAK-cell-mediated lysis with time was evaluated in 51Cr release assays of varying duration. This study shows that LAK-mediated lysis of T24 and Daudi cells was closely related and LAK cytotoxicity measured in 51Cr release assays against these two target cells may be measurement of similar effector-to-target cell interactions.     

Interleukin-6 is a Mediator of TNF-α Regulation of LAK Cell Function

TNF-α at 50–100 U/ml synergizes with IL-2 in enhancing LAK activity and IL-6 production in low-dose IL-2 (1–10 U/ml) culture of human PBL. High-dose TNF-α (≥200 U/ml) has less effect and even sometimes resulted in lowering of both LAK activity and IL-6 production below control levels. TNF-α-mediated regulation of low-dose IL-2 activation occurs even at late stages (effector phase) of LAK development. IL-6, as previously reported, acts at late stages of low-dose IL-2 culture to enhance LAK, but does not stimulate TNF-α production. The combined addition of TNF-α and IL-6 to late stages of IL-2 culture does not produce any additive or synergistic effect on LAK. We tested for the relative roles of TNF-α and IL-6 in late stage regulation of LAK development with antibodies (Abs) to these cytokines. Anti-IL-6 Ab abrogates late phase LAK enhancement by TNF-α, while anti-TNF-α Ab has no effect on IL-6 augmentation of LAK cytotoxicity, IL-2 added to PBL culture at doses greater than 10 U/ml induces production of both TNF-α and IL-6. Addition ofanti-TNF-α Ab at late stages of high-dose IL-2(≥20U/ ml) culture decreases both LAK cytotoxicity and IL-6 production, and the inhibition of LAK is reversed by the addition of IL-6. By contrast. anti-IL-6 Ab decreases LAK cytotoxicity, but does not alter TNF-α production, and the inhibition of LAK is not reversed by addition of TNF-α. These data indicate that TNF-α is important for both LAK development and IL-6 secretion in PBL, and that IL-6 is the proximate mediator in TNF-α regulation of these cytotoxic cell functions.     

Optimal methods for generating expanded lymphokine activated killer cells capable of reducing established murine tumors in vivo

The systemic administration of lymphokine activated killer (LAK) cells and recombinant interleukin-2 (RIL-2) is effective in reducing the number of established pulmonary and hepatic metastases from multiple murine tumors and has recently been shown to be effective in mediating the regression of metastatic cancer in humans as well. The generation of sufficient numbers of LAK cells for the effective therapy of human tumors remains a major obstacle to the widespread application of this immunotherapeutic approach. We have thus studied methods for the in vitro expansion of LAK cells effective in immunotherapy. Our previous studies used LAK cells generated in culture with RIL-2 for 3 days. LAK cells cultured in RIL-2 for 5 or 7 days were not significantly different from cells cultured for 3 days either in the number of cells obtained, their in vivo cytotoxicity or their in vivo therapeutic effectiveness. When day 3 LAK cells were transferred to fresh culture medium containing 1000 U/ml of RIL-2, a highly reproducible expansion of these cells was obtained. By day 5, cell numbers expanded 9.6 +/- 0.8-fold (mean +/- SEM; n = 36) and by day 8, cells expanded 15.1 +/- 1.0-fold (n = 19). In 4 h 51Cr release assays against fresh tumor target cells, day 3 LAK cells had a mean of 13 lytic units/10(6) cells in 24 experiments. Day 5 expanded LAK cells had a mean of 30 lytic units/10(6) cells in 13 experiments (P less than 0.05 compared to day 3 LAK cells) and day 8 expanded LAK cells had a mean of 11 lytic units/10(6) cells in 6 experiments (P = NS compared to day 3 LAK cells) When day 5 and day 8 expanded LAK cells were infused in vivo with RIL-2, they were found to significantly reduce the number of experimentally induced pulmonary metastases as effectively as non-expanded conventional day 3 LAK cells. Similar findings were documented in experiments against hepatic metastases. These experiments demonstrate that LAK cells could expand a mean of 15-fold in vitro in RIL-2 and maintain their anti-tumor therapeutic effectiveness when adoptively transferred. These experiments suggest methods for generating increased numbers of cells for use in the adoptive immunotherapy of human cancers and may substantially reduce the need for repeated leukophereses of cancer patients undergoing this therapy.