Autologous tumor specific immunotherapy of refractory cancers with ex vivo-generated T cells stimulated by autologous tumor cell

OBJECTIVES: Autologous tumor-cell stimulated cytotoxic T lymphocytes (AuTLs) were prepared from peripheral blood T cells and the T cells were activated ex vivo over a 2-week culturing process in the presence of IL-2 and autologous biopsied tumor-cells from advanced cancer patients. These AuTLs may have potential for efficacy as a locoregional therapy in patients with refractory cancer. METHODS: Twenty-nine of 35 cancer patients (13 esophagus, 5 lung, 3 stomach, 4 breast, 1 melanoma) were enrolled in an early Phase II clinical trial. The patients received direct locoregional intratumoral injection of AuTLs biweekly through medical endoscope or intraarterial infusion reservoir system. Mean 0.25 x 10(9) AuTLs were injected 1 x /2 weeks for 6 weeks. RESULTS: Adverse events related to AuTL were minimal. AuTLs specific for autologous tumor cells were observed in 12 of 29 patients. Seven of these 12 patients (58.3%) had partial response (PR) or stable disease (SD). In contrast, 8 of 23 (34.8%) remaining patients treated by non-specific AuTLs had SD. Infiltration of T effector cells was significantly increased on the biopsied tumor specimens in the immunohistological studies. Furthermore, 11 patients receiving systemic infusion of non-specific LAK/NK T cells without autologous tumor-cell stimulation only had 2 SDs (18.2%). CONCLUSIONS: Our results demonstrated the clinical potential of intra-peritumoral administration of AuTLs. Thus, locoregional immunotherapy with autologous tumor specific AuTLs may be more effective than systemic adoptive immunotherapy using intravenous infusion of autologous tumor non-specific LAK/NK T cells for the treatment of solid cancers.     

Local administration of autologous lymphokine-activated killer cells and recombinant interleukin 2 to patients with malignant brain tumors

Lymphokine-activated killer cells (LAK cells) were induced from lymphocytes from patients with malignant glioma by using interleukin 2 (IL-2), and their killing activity was examined. Their LAK activity against Daudi cells was 66.2 +/- 13.1% and 48.7 +/- 12.7% against self glioma cells, 54.4 +/- 10.1% against K562 cells, 43.1 +/- 7.9% against Raji cells, and 33.5 +/- 16.2% against allogeneic glioma cells. The phenotype of these LAK cells was Leu 1 (++), 2a (+/-), 3a (++), 7 (+), and 11 (++). The phenotype of precursor LAK cells, on the other hand, was Leu 1 (-), 2a (-), 3a (+), 7 (-), and 11 (++). Other activated killer cells, including LAK cells, phytohemagglutinin-activated killer cells, autoactivated killer cells, and their precursor LAK cells, were studied serologically in order to identify their phenotypic characteristics. From these data, the LAK cell populations were considered to be polyclonal. Using these LAK cells plus IL-2, local adoptive immunotherapy was undertaken in 23 patients with recurrent malignant glioma. We injected, that is, autologous LAK cells plus IL-2 directly into the cavities of the brain tumors; 1.2 to 324 x 10(8) LAK cells per ml and 0.8 to 5.4 x 10(3) units of IL-2 were directly injected into the brain tumor by using an Ommaya reservoir. Definite tumor regression, improvement of some clinical symptoms, and continuous remission over 6 mo or more were observed in six, nine, and three patients, respectively. There were no marked side effects, except for slight fever and chill, in eight and three patients, respectively. These results suggested the possibility of induction of a sufficient number of LAK cells from the lymphocytes of the patients with recurrent malignant glioma, indicating that local adoptive immunotherapy by direct injections of LAK cells and IL-2 into the brain tumor will prove to be an effective means of immunotherapy. Additional follow-up of the patients will be required before its therapeutic value can be established.     

Recombinant interleukin-2 and adoptive immunotherapy alternated with dacarbazine therapy in melanoma: a National Biotherapy Study Group trial

We evaluated adoptive cellular therapy with recombinant interleukin-2 (rIL-2) plus lymphokine-activated killer (LAK) cells alternating with sequential dacarbazine chemotherapy in 27 patients with metastatic melanoma. rIL-2 was given to the patients as a 5-day continuous-infusion priming cycle followed by 1 day of rest, 4 days of leukapheresis for in vitro LAK cell expansion, and then 4 1/2 days of continuous rIL-2 infusion in conjunction with reinfusion of LAK cells during the first 3 days of the continuous infusion. Two weeks later, patients received dacarbazine (1,200 mg/m2) chemotherapy. Two patients achieved complete remission, and five achieved a partial remission for a response rate of 26% (95% confidence interval = 12%-47%). Three patients had mixed responses. The partial and mixed responses were brief, ranging from 1 month to 6 months, whereas the two complete responses have been sustained for 13+ and 24+ months. There were no additive toxic effects except for thrombocytopenia, which delayed treatment in two patients. Alternating adoptive immunotherapy and dacarbazine chemotherapy appear to be reasonably tolerated by patients, but the response rate is not clearly better than that achieved with other rIL-2 regimens or with chemotherapy alone.     

原发性肝癌的免疫状态及其过继免疫治疗

1993年3月～1995年12月，20例无手术切除指征的肝癌患者接受rIL－2／LAK过继免疫治疗，其中6例（30％）获部分缓解。16例肝癌患者于治疗前后行免疫功能测定，结果显示：1）原发性肝癌病人外周T细胞亚群及NK活性是明显抑制状态（P＜0．001）；2）患者经过过继免疫治疗后，T细胞工群及NK细胞活性明显改善。上述结果表明原发性肝癌病人是明显免疫抑制状态，采用rIL－2／LAK区域过继免疫治疗有效。     

A phase II study of interleukin-2 and lymphokine-activated killer cells in patients with metastatic malignant melanoma

Thirty-six patients with metastatic melanoma were entered into a study of the therapeutic efficacy of adoptive immunotherapy with high-dose interleukin-2 (IL-2) and lymphokine-activated killer (LAK) cells. Thirty-two patients who received all components of the therapy are evaluable for response, and all patients are evaluable for toxicity. Sites of disease included lung, liver, subcutaneous nodules, and intra-abdominal metastases. One complete response (CR) and five partial responses (PRs) resulted from treatment (19% response rate). The median response duration was 5 months, with the durable CR continuing at 31+ months and one durable PR continuing for 13 months. Sites of response included lung, liver, subcutaneous nodules, and lymph nodes. Response, response duration, or site of response did not correlate with the total dose of IL-2 administered, rebound lymphocytosis, or the number of LAK cells infused. Toxicity included hypotension, fluid retention with a "capillary leak syndrome" in most patients, and transient multiorgan dysfunction that resolved promptly after the completion of therapy. Adverse cardiac events occurred in 16% of patients, with one myocardial infarction leading to a death. This study confirms the activity of the initial IL-2/LAK cell regimen in metastatic melanoma reported by Rosenberg et al, supporting the concept of adoptive immunotherapy as an important new treatment approach for this disease.     

Local adoptive immunotherapy using lymphokine-activated killer cells and interleukin-2 against malignant pleural mesothelioma: report of two cases.

Malignant pleural mesothelioma is refractory to conventional therapy. We tried local adoptive immunotherapy using lymphokine-activated killer (LAK) cells and interleukin-2 (IL-2) to control malignant pleural effusion due to mesothelioma in two patients: Case 1 was that of a 69-year-old man, and Case 2 that of a 49-year-old woman with complicating chronic idiopathic thrombocytopenic purpura. A systemic survey revealed no sign of metastasis in either case. Intrapleural instillations of 6.7 x 10(9) autologous LAK cells in Case 1, or 11.3 x 10(9) allogeneic LAK cells in Case 2, with daily injections of IL-2 resulted in reductions of the pleural effusions in each case and in a decline in the level of hyaluronic acid in the effusion, in Case 1. The instillations of autologous and allogeneic LAK cells were well tolerated. The results suggest that local adoptive immunotherapy could be useful in the treatment of malignant effusion due to mesothelioma.     

Long-term prognosis of hepatocellular carcinoma patients treated with adoptive immunotherapy

Adoptive immunotherapy was performed for patients with multiple hepatocellular carcinoma (HCC) using LAK cells via the hepatic arterial catheter. One case study: A 45-year-old male patient was performed an absolute-non-cure operation. The operation was a success. However, some residual tumors remained in the liver. After the operation, adoptive immunotherapy was performed for 7 times in 5 weeks. The total inoculated LAK cells were 6.9x10(9). After the adoptive immunotherapy, no residual tumors were detected in the liver. He survived for 7 years in remission. Our results show that adoptive immunotherapy with LAK cells is useful and effective for patients with multiple HCC.     

Locoregional adoptive immunotherapy using LAK cells and IL-2 against liver metastases from digestive tract cancer

We investigated the clinical efficacy of locoregional and systemic adoptive immunotherapy (AIT) with or without interleukin-2 (IL-2) against solid metastatic lesions from digestive tract cancer. Eighteen patients, who were treated with more than 10(10) lymphokine-activated killer (LAK) cells, were enrolled in this study. Seven of the 18 patients received hepatic arterial infusion (HAI) of LAK cells with or without IL-2 against metastatic liver tumors (locoregional therapy group). The remaining 11 patients received systemic transfer of LAK cells with IL-2 against metastatic lesions located in organs other than the liver (systemic therapy group). Three of 7 locoregional therapy group patients showed clinically significant tumor regressions that were evaluated as being equivalent to partial response (PR). Two of the 11 systemic therapy group patients showed significant tumor regressions, but this response rate was much lower than that of the locoregional therapy group. The 2 effective cases in the systemic therapy group were esophageal cancer patients. Locoregional AIT with or without IL-2 against liver metastases from digestive tract cancer could be an effective therapeutic modality in some patients who are refractory to conventional therapies (e.g., chemotherapy and radiotherapy). It is necessary to find a new way to augment the anti-tumor effect of this therapy in combination with prior or concomitant chemotherapy.     

Augmentation of interleukin-2 immunotherapeutic effects by lymphokine-activated killer cells and allogeneic stimulation in murine tumor cells

Interleukin-2 (IL-2) and lymphokine-activated killer (LAK) cells were used in intraperitoneal and pulmonary tumor models in C57BL/6 mice. To maintain the immunotherapeutic effects of IL-2 plus LAK treatment but reduce its toxicity, ways were sought to augment IL-2 effects. The investigation showed that the adoptive transfer of LAK cells was a prerequisite for successful therapy of intraperitoneal cancer. When LAK cells were given on consecutive days within one course of immunotherapy, antitumor efficacy was augmented with additional doses of LAK cells. However, with the reduction of 1 complete cycle of IL-2 + LAK cells, no further reduction in intraperitoneal tumor was observed as compared to the reduction after 2 or 4 cycles. LAK cells generated from splenocytes of mice that had received an allogeneic tumor challenge 1 week earlier exerted a highly increased cytotoxicity as compared to normal LAK cells. Furthermore, the potentiation effect of an allogeneic response of the host at the tumor site was demonstrated by decreased numbers of lung implants and improved survival in mice given mixtures of syngeneic and allogeneic tumor cell suspensions. An alloimmune response within the microenvironment of tumor tissue markedly enhanced the antitumor effect of IL-2 against the syngeneic tumor. It was concluded that there is a fundamental need to improve the recruitment of adoptively transferred LAK cells or LAK precursors into tumor tissue. This may be the next step required in the further development of IL-2 and LAK immunotherapy.     

Interleukin-2 enhances biopterins and catecholamines production during adoptive immunotherapy for various cancers

Biopterins production during three different protocols for adoptive immunotherapy for human cancer was investigated. Adoptive immunotherapy treatment with interleukin-2 (IL-2) was carried out for 13 patients with malignant melanoma; eight with metastatic renal cell carcinoma; and three with metastatic colon cancer. The authors estimated total biopterins in plasma and lymphokine (IL-2)-activated killer cells (LAK) from these patients before and during various treatment phases to determine if increased biopterins production reflects leukocyte activation by IL-2 or antitumor activity. They noted an increased synthesis of total "biopterins," i.e., biopterin; 7,8-dehydrobiopterin; and L-neopterin in LAK cells and plasma which correlated with IL-2 exposure. Mean plasma biopterins were normal (1.2 +/- 0.5 ng/ml) before therapy; in contrast, biopterins increased significantly to 3.4 +/- 1.9 ng/ml and 3.9 +/- 1.9 ng/ml during IL-2 and IL-2 + LAK treatment each, respectively. Similar biopterin elevations were noted irrespective of the different adoptive immunotherapy protocols used. Elevated biopterins decreased to normal levels (1.2 +/- 0.7 ng/ml) when IL-2 treatment was omitted. Tumor regression with adoptive immunotherapy did not correlate with increased plasma biopterins. Increased biopterins production was also associated with increase in plasma catecholamine after IL-2 treatment during adoptive immunotherapy. Conceivably increased biopterins, induced by IL-2 activation of a leukocyte population, is a cell-mediated consequence not necessarily serving as a signal for the antitumor effect associated with adoptive immunotherapy.     

白介素－2的Ⅱ期临床试验报告

共１５９例各种类型的恶性肿瘤病人进入了Ⅱ期临床试验。２５例病人接受了白介素－２（ＩＬ－２）单独全身治疗（静脉或皮下注射）；６０例病人接受了ＩＬ－２＋ＬＡＫ细胞全身性治疗；４１例癌性胸水病人接受了ＩＬ－２胸腔内灌注；６例癌性腹水病人接受了ＩＬ－２腹腔灌注；２７例病人接受了ＩＬ－２瘤内注射。单用ＩＬ－２全身治疗的病人没有病例获得临床缓解，２３晚期肾癌接受了ＩＬ－２＋ＬＡＫ细胞治疗，５例获得部分缓解，有效率２２％：癌件胸水和腹水的有效率分别为６８％和６７％：ＩＬ－２瘤内注射的有效率为３０％。Ｔ４／Ｔ８比值、ＮＫ细胞活性和ＬＡＫ细胞活性在全身性ＩＬ－２治疗后均有显著升高，并有统计学意义。病人接受本试验所用的ＩＬ－剂量后的毒副反应主要为发热、畏寒或寒战、疲乏，全组病人均无发生严重低血压、液体潴留等毛细血管渗漏现象。     

Enhanced antimetastatic activity of lymphokine-activated killer cells purified and expanded by their adherence to plastic

We have recently reported a simple and reproducible technique for the purification and rapid expansion of homogeneous populations of large granular lymphocytes expressing a natural killer cell phenotype and high levels of broad antitumor cytotoxic activity [lymphokine-activated killer (LAK) activity]. This technique exploits the observation that, in the presence of recombinant interleukin 2 (rIL-2), large granular lymphocytes/natural killer cells become adherent to plastic surfaces, actively proliferate, and acquire high levels of LAK activity. Because of their adherent properties these cells have been termed adherent LAK or A-LAK cells. The present studies investigate the antimetastatic effects of A-LAK cells in a syngeneic rat model of experimental pulmonary and hepatic metastases. For pulmonary metastases, F344 rats received i.v. injections with a natural killer-resistant mammary adenocarcinoma, MADB106, and, for hepatic metastases, animals received an intrasplenic injection of MADB106 tumor cells followed by surgical splenectomy. Three days later, the animals were treated with A-LAK cells alone, A-LAK cells plus rIL-2, or rIL-2 alone. These treatments were compared to immunotherapy using standard cultures of LAK cells (unfractionated spleen cells) and rIL-2. The results indicate that the administration of unfractionated LAK cells plus interleukin 2 (IL-2) was effective in reducing established lung or liver metastases in this rat model. However, the results also indicate that purified populations of A-LAK cells in combination with rIL-2 demonstrate dramatic and superior antimetastatic effects when compared to LAK cells cultured under standard conditions. The antimetastatic effects of standard LAK cells or A-LAK cells plus IL-2 translated into significant survival benefits compared to animals receiving no therapy or IL-2 therapy alone. Survival after therapy with A-LAK cells plus IL-2 was significantly prolonged compared to treatment with standard LAK cells. These data suggest that purified populations of LAK cells (derived from natural killer cells) may prove superior for adoptive immunotherapy in the clinical setting.     

Clinical effects of chemoimmunotherapy for patients with peritoneal carcinomatosis

The present study was undertaken to determine whether chemoimmunotherapy using activated killer cells is better than chemotherapy alone for cancer patients with peritoneal carcinomatosis. Thirty-one cancer patients received adoptive immunotherapy by activated killer cells and chemotherapy by anticancer drugs selected by a chemosensitivity test (chemoimmunotherapy group), and another 31 cancer patients received chemotherapy (chemotherapy group). The regimen of chemotherapy was determined by the results of a chemosensitivity test in both groups. The clinical effects including response rate and survival were assessed. Five patients (16.1%) achieved complete response (CR), and 17 patients (54.8%) partial response (PR) in the chemoimmunotherapy group (response rate: 22/31 patients = 71.0%), whereas 4 patients (12.9%) achieved CR, and 5 patients (16.1%) PR in the chemotherapy group (response rate: 9/31 patients = 29.0%). The response rate was higher in chemoimmunotherapy group than in chemotherapy group (p<0.05). However, no difference was observed in survival between the two groups. Therefore, it is necessary to develop methods to induce more potent killer cells for adoptive immunotherapy.     

LAK cells and cancer

The effectiveness of LAK cells (lymphokine-activated killer cells) on malignant tumors in vivo and in vitro was discussed. LAK cells induced from lymphocytes by interleukin-2 (IL-2) were able to kill target malignant cells in a nonspecific manner. Combination of IL-2 enhanced LAK activity. Adoptive immunotherapy with LAK cells and IL-2 carried out in the USA has produced effective results in several cases; complete regression of skin metastases of malignant melanoma and partial regression of other malignancies. However, high doses of IL-2 mediated a toxic side effect, capillary permeability leak syndrome. Our studies have revealed that LAK cells after one to two weeks incubation do not require such a high concentration of IL-2, and that adoptive immunotherapy using such, LAK cells and IL-2 can be carried out safely.     

Lymphokine-activated killer (LAK) cells. Analysis of factors relevant to the immunotherapy of human cancer

Lymphokine-activated killer (LAK) cells can be generated by incubating fresh peripheral blood lymphocytes (PBL) in Interleukin-2 (IL-2). LAK cells kill fresh autologous and allogeneic human tumor cells in vitro. This study analyzes aspects of LAK cells that make them a promising candidate for the adoptive immunotherapy of human cancer. LAK cells can be generated from PBL of normal individuals and tumor-bearing patients. Pure, recombinant IL-2 generates LAK cells capable of killing a wide variety of tumors including sarcomas and cancers of the colon, pancreas, adrenal gland, and esophagus. Thirty-six of 41 (88%) fresh, noncultured, human tumor cell suspensions prepared from surgical specimens were lysed by LAK cells in a standard 4-hour chromium-release assay. Normal PBL were not killed. LAK cells can be expanded in vitro for periods longer than 2 months, potentially more than 10(20)-fold, while maintaining lytic ability. These results and the demonstrated efficacy of LAK cells in the therapy of murine tumors make LAK cells a candidate for clinical use in the adoptive immunotherapy of human cancer.     

The use of interleukin-2 and lymphokine-activated killer cells for the treatment of patients with non-Hodgkin's lymphoma.

PURPOSE: The study was undertaken to assess whether immunotherapy regimens with bolus high-dose interleukin-2 (IL-2) alone or with lymphokine-activated killer (LAK) cells are active in previously treated, relapsed patients with non-Hodgkin's lymphoma. PATIENTS AND METHODS: Nineteen patients with low- or intermediate-grade lymphomas were treated with bolus high-dose IL-2 alone (11 patients) or IL-2 with LAK cells (eight patients). IL-2 was administered by intravenous bolus infusion at 720,000 IU/kg every 8 hours. Eight patients had low-grade histologies; 11 patients were intermediate-grade. Eighteen patients had received second- or third-generation combination chemotherapy, and eight had also received radiation. All 19 relapsed after a median of two chemotherapy regimens. RESULTS: Four responses were observed, three partial and one complete, in patients with follicular histologies who received IL-2 with LAK cells. Response durations were 10, 16, 16, and 26 months, and three responders were re-treated after relapse with subsequent disease control for an additional 16, 39+, and 2+ months, respectively. CONCLUSION: High-dose, bolus IL-2-based immunotherapy with LAK cells may be an effective treatment for patients with non-Hodgkin's lymphoma and merits further testing with larger numbers of patients in phase II trials.     

Antitumour effect of intratumoral injection of human recombinant interleukin-2 in patients with hepatocellular carcinoma: a preliminary report

Five hepatoma patients with small resectable tumour received an intratumoral injection of recombinant interleukin-2 (rIL-2) once weekly over 2–4 weeks (1.05 × 10⁶−3.6 × 10⁶ U in total per patient). Tumour regressions of 32% and 57% were observed in two patients at day 42 after the first rIL-2 injection. No response was observed in two patients and disease progressed in one. Lymphokine-activated killer (LAK) activity was enhanced and Leu-11⁺ cells increased in the peripheral blood in the patients with 32% and 57% tumour regression after rIL-2 therapy. However, LAK activity, Leu-7⁺ cells were reduced in the patient who progressed. No consistent changes in Leu-2a⁺ cells and Leu-3a⁺ cells were demonstrated. In the three patients showing no response or 32% tumour regression, hepatic segments containing tumour were resected; histologically the tumour showed severe necrosis and lymphocytic infiltration in the patient with 32% tumour regression but mild or moderate changes in the other two. IL-2 mediated tumour killing can be induced in tumours by intratumoral injection of rIL-2, leading to tumour regression.     

Effects of allogeneic LAK cells on the function of immune system of the recipients

SHR rats, 1 week of age, were i.p. inoculated with allogeneic JB LAK cells generated by 3-day incubation of spleen cells of JB rats in CM-IL 2. The spleens were removed 4 and 12 weeks later and their cells were tested for proliferative potential to mitogens and their response and production of IL2. The results demonstrated that the allo-LAK recipients showed no signs of acute or chronic GvH disease but showed immune response equivalent to or higher than the normal controls. Severe functional defects were observed in the newborn SHR rats after i.p. inoculation of allogeneic fresh spleen cells from JB rats. The results strongly suggest that allogeneic LAK cells be ineffective in terms of induction of GvH disease or GvH associated immunodeficiencies (GvHID). Therefore, this might be promising in clinical trials on cancer adoptive immunotherapy with allogeneic, instead of autologous, LAK cells.     

A new approach to generating antitumor effectors for adoptive immunotherapy using human adherent lymphokine-activated killer cells

Lymphocytes from human peripheral blood incubated with interleukin-2 (IL2) develop lymphokine-activated killer (LAK) activity with the ability to kill a wide variety of tumor cells in a non-major histocompatibility complex-restricted manner. Adoptive immunotherapy with LAK cells and IL2 has been reported to lead to a regression of solid tumors in some patients with advanced malignancies. Aiming to improve the effectiveness of clinical adoptive immunotherapy, we developed a procedure for selective enrichment from human blood mononuclear cells (MNC) of IL2-activated antitumor effector cells. These cells, termed adherent LAK (A-LAK) cells because of their characteristic property of adherence to plastic, demonstrated both higher proliferative potential and greater antitumor cytotoxicity than unseparated MNC. Human A-LAK cells represented only 1 to 4% of IL2-activated MNC at 24 h but expanded from 130- to 1100-fold in 20 days. They comprised a population highly enriched in CD3-Leu19+ effector cells with antitumor activity against fresh human solid tumor cells and established cell lines. A-LAK cells retained antitumor activity for up to 14 days when cultured in the presence of IL2. They also mediated antibody-dependent cytotoxicity. Large-scale generation of A-LAK cells from the blood of patients with cancer proved feasible and should yield populations that are effective in vivo at lower doses than those required with unseparated LAK cells. This offers the potential for improving the antitumor effects, reducing the toxicity, and facilitating the administration of adoptive immunotherapy in humans. A Phase I/II clinical trial utilizing A-LAK cells and IL2 in patients with melanoma and renal cell carcinoma is now in progress.     

Adoptive immunotherapy of human cancer using low-dose recombinant interleukin 2 and lymphokine-activated killer cells

The adoptive transfer of recombinant-methionyl human interleukin 2 (rIL-2)-activated autologous peripheral blood mononuclear lymphokine-activated killer (LAK) cells to cancer patients is being evaluated as an alternative to conventional cancer therapy. We have independently developed an alternative regimen to previously reported adoptive immunotherapy protocols using rIL-2 and LAK cells which features the prolonged administration of low-dose rIL-2 (30,000 units/kg) and an automated, entirely enclosed system of peripheral blood cell procurement, culture, harvest, and reinfusion of activated cells. The cell culture system was tested with a murine tumor model in which LAK cells generated in plastic culture bags were reinfused into tumor-bearing mice. Tumor regression was as effective with cells activated in the bags as in conventional culture flasks. Twenty-eight cancer patients were treated for 5 consecutive days with low-dose rIL-2, followed by leukapheresis, infusion of LAK cells, and prolonged IL-2 administration. At least 50% tumor regression was observed in 46% of all patients treated. These data imply that human peripheral blood mononuclear cells retain fully their capacity for rIL-2-induced activation and effector cell function under this alternative approach, and further, that a low-dose rIL-2 regimen with markedly reduced toxicities can be as effective as high-dose rIL-2 regimens if low-dose rIL-2 is given for a prolonged period of time following LAK cell infusion.