Interleukin-12 Augments the Generation of Autologous Tumor-reactive CD8+ Cytotoxic T Lymphocytes from Tumor-infiltrating Lymphocytes

Human tumor-infiltrating lymphocytes (TIL) were obtained from breast cancer, renal cancer or neuroblastoma to investigate the generation of autologous tumor-reactive CD8⁺ cytotoxic T lymphocytes (CTL). When TIL were cultured with interleukin (IL)-2 (100 U/ml), the growth of TIL peaked around 8–10 days after the initiation of culture. In contrast, the proliferation of TIL cultured with IL-2 plus IL-12 peaked around 4–5 days after culture and tumor cells rapidly disappeared from the culture. To determine the generation of autologous tumor-reactive CD8⁺ CTL, TIL-derived CD8⁺ T cells were separated by FACStar. Both IL-2-activated and IL-2 plus IL-12-activated TIL-CD8⁺ T cells showed the same level of lymphokine-activated killer activity against a variety of tumor cells. However, TIL-CD8⁺ T cells activated with IL-2 plus IL-12 revealed greatly augmented cytotoxicity against autologous tumor cells compared with that induced by IL-2 alone. The autologous tumor cell-killing activity of TIL-CD8⁺ CTL was significantly inhibited by the addition of F(ab)₂ anti-CD3 monoclonal antibody, indicating that these CTL recognize autologous tumor antigen through T cell receptor. These results imply that IL-12 is a novel cytokine which facilitates the generation of autologous tumor-reactive CD8⁺ CTL from TIL.     

Effects of Interleukin-12 on the Induction of Cytotoxic T Lymphocytes from the Regional Lymph Node Lymphocytes of Patients with Lung Adenocarcinoma

Lung cancer-specific cytotoxic T lymphocytes (CTL) were induced by repeated stimulations of regional lymph node lymphocytes (RLNL) in lung cancer patients with either autologous or HLA-A-locus-matched tumor cells. To investigate the effect of interleukin-12 (IL-12), IL-12 was added during the stimulation of RLNL from HLA A24 / adenocarcinoma patients with either autologous tumor cells or HLA A24-positive adenocarcinoma cells (PC-9) in combination with, or instead of interleukin-2 (IL-2), and then the cytotoxic activity, cytokine production and populations of the lymphocyte subsets were examined. The addition of IL-12, or the substitution of IL-2 by IL-12 was found to enhance the cytotoxic activity and the cytokine production (IFN-γ, GM-CSF) of the CTL as compared with IL-2 alone. The cytotoxic activity and cytokine production were both partially inhibited by anti-MHC-class I monoclonal antibody. The CTL thus induced by IL-12 had a higher proportion of CD3⁺/CD56⁺ cells than the CTL induced with IL-2 alone. The positively selected CD8⁺/CD56^– lymphocytes showed PC-9-specific cytotoxic activity, because the population did not show any cytotoxicity to K562 or A549 (HLA-A26/A30). However, the CD3⁺/CD56⁺ lymphocytes were cytotoxic to both PC-9 and K562. In conclusion, IL-12 is considered to be a useful cytokine for both the induction of lung-cancer specific CTL and the augmentation of non-MHC-restricted cytotoxicity against tumor cells, and may be applicable for adoptive immunotherapy using CTL.     

Direct Activation of Human CD8+ Cytotoxic T Lymphocytes by Interleukin-18

Direct activation of human cytotoxic T lymphocytes (CTL) by interleukin (IL)-18 was observed in a system in which CTL effective against autologous tumor cells were generated. Peripheral blood mononuclear cells (PBMC) from tumor-bearing patients, after removal of natural killer (NK) cells, were cultured in a medium containing IL-1, -2, -4, and -6, with or without IL-18, and stimulated with autologous tumor cells. IL-18 increased the activity of the CTL and the proportion of autologous CD8⁺ T cells present after 28 days in the induction culture. When purified CD8⁺ T cells were cultured in the presence of IL-18 and IL-2 for 7 days, the CTL showed enhanced cytotoxic activity against autologous tumor cells. Moreover, a purified CD8⁺ T cell population, which did not exhibit any apparent cytotoxic activity against autologous tumor cells, displayed cytotoxic activity after 7-day incubation with IL-18. These results suggest that IL-18 may be useful to generate autologous CTL in humans and may thereby contribute to adoptive immunotherapy for tumors.     

Histocompatibility Leukocyte Antigen-A2-restricted and Tumor-specific Cytotoxic T Lymphocytes from Tumor-infiltrating Lymphocytes of a Patient with Testicular Embryonal Cancer

T lymphocytes play an important role in tumor rejection. To understand T cell-mediated specific immunity at the tumor site of testicular embryonal cancer, we investigated whether interleukin-2 (IL-2)-activated tumor-infiltrating lymphocytes (TIL) of a patient with testicular embryonal cancer show histocompatibility leukocyte antigen (HLA)-class I-restricted and tumor-specific cytotoxicity. We established a CD3⁺CD4^-CD8⁺ cytotoxic T lymphocyte (CTL) line from the IL-2-activated TIL of a 37-year-old patient with testicular embryonal cancer. A 6 h ⁵¹Cr-release assay was performed to measure the cytotoxicity of the CTL. The CD3⁺CD4^-CD8⁺ CTL line showed cytotoxicity against HLA-A2⁺ tumor cells, including freshly isolated autologous tumor cells, adenocarcinoma cell lines from various organs (lung, breast, pancreas, colon and kidney) and squamous cell carcinomas (esophagus and oral cavity). No other cell lines examined, including an autologous tumor cell line and HLA-A2" tumor cell lines, were lysed by this CTL line. These results suggest the existence of HLA-A2-restricted and tumor-specific CTL at the tumor site of testicular embryonal cancer.     

Sequential T Cell Response Involved in Tumor Rejection of Sarcoma, Meth A, in Syngeneic Mice

We investigated the type of T cell response involved in Meth A tumor rejection in primary immune and hyperimmune syngeneic mice. It was found that a CD4⁺ T cell-mediated delayed-type hypersensitivity (DTH) response activating non-specific killer cells such as macrophages, NK and LAK cells, without a specific CD8⁺ cytotoxic T lymphocyte (CTL) response, was the major immune response leading to Meth A tumor rejection in primary immune mice. In contrast, the specific CD8⁺ CTL response was the major response leading to the tumor rejection, in addition to CD4⁺ T cell-mediated DTH response, in hyperimmune mice. Analysis of CD4⁺ T cell clones established from primary immune and hyperimmune spleen cells indicated that a CD4⁺ T cell clone (C9) of primary immune mice (although only one clone was established) was of Th1 type, and induced cytotoxicity in accessory cells by classic DTH in vitro. Eight CD4⁺ T cell clones were established from hyperimmune spleen cells. Six out of the eight clones were of the Th2 type and two were Th0-like. However, no Th1-type CD4⁺ T cell clone was established from hyperimmune spleen cells. All of these CD4⁺ T cell clones, even the Th2-type clones, were capable of inducing cytotoxicity in vitro in T cell-depleted accessory cells, as in an in vitro DTH response. We postulate on the basis of these results that the T cell response leading to Meth A tumor rejection in vivo sequentially changed from a CD4⁺ T cell-mediated classic DTH response to a CD8⁺ CTL response, in addition to a cellular response mediated probably by Th2-type cells, during the process of repeated immunization.     

Lysis of Fresh Human Tumor Cells by Autologous Peripheral Blood Lymphocytes and Tumor-infiltrating Lymphocytes Activated hy PSK

The protein-bound polysaccharide PSK was tested for the ability to induce in vitro autologous tumor killing (ATK) activity in human cancer patients. Peripheral blood lymphocytes (PBL) and tumor-infiltrating lymphocytes (TIL) demonstrated various levels of cytotoxicity against autologous, freshly isolated tumor cells. When PBL and TIL were cultured overnight with PSK, ATK activity was induced in previously non-reactive cases and augmented in previously reactive samples. The PSK effect was observed with PSK concentrations of 10–100 μg/ml that could be obtained in the blood of cancer patients who received standard oral administration of PSK. The manifestation of PSK-induced ATK required active cell metabolism and RNA and protein syntheses, but not DNA synthesis of lymphocytes. PSK-induced enhancement of ATK was not abrogated by monoclonal antibodies (mAb) directed against interferon (IFN)α or IFNγ-. In addition, mAb that neutralized interleukin-2 (IL-2) or mAb reactive with α-chain or β -chain of IL-2 receptors (IL-2R) had no effect on PSK-induced ATK activity. Supernatants from PSK-stimulated lymphocyte cultures did not induce ATK. Cell fractiona-tion experiments revealed that CD3^-CD16⁺ large granular lymphocytes (LGL) and/or CD3⁺CD16^- T lymphocytes were responsible for both spontaneous and PSK-induced ATK. PSK-activated LGL, but not T lymphocytes expressed lysis of fresh allogeneic tumor cells. These results indicate that PSK activates PBL and TIL to exhibit ATK independently of IL-2/IL-2R systems.     

Brefeldin A Blocks the Cytotoxicity of T Cell Receptor α/β and γ/δ Cytotoxic T Lymphocyte Clones Reacting against Human Autologous Cancer Cells

We studied the effector mechanism of T cell receptor (TCR) α/β - and γ/δ -type cytotoxic T lymphocyte (CTL) clones that react with human autologous tumor cells. Treatment of tumor cells with a fungal antibacterial reagent, brefeldin A (BFA), resulted in the inhibition of cytotoxicity of an autologous tumor (HST-2)-specific CD8⁺ TCR α/β -type CTL, TcHST-2. Other anti-metabolites such as chloroquine, cycloheximide and colchicine did not affect the cytotoxicity. The cell-surface antigen expression, including MHC class I molecules, was not influenced by BFA treatment. Furthermore, BFA did not influence the cytotoxicity of lymphokine-activated killer cells and natural killer cells. Since BFA blocks the transport of peptides from endoplasmic reticulum to the Golgi apparatus, the above data suggest that BFA could affect washing out of the peptide fragments from the MHC class I groove. Consequently, target tumor cells were protected from killing by CTL, Moreover, we obtained a CD4⁻, 8⁻, TCR γ/δ -type (Vδ1⁺) CTL clone, TcHOT, that reacts against an autologous ovarial carcinoma, HOT. BFA could also inhibit this cytotoxicity, and it is likely that different presenting molecules other than MHC class I proteins participate in the cytotoxicity of this TCR gm/δ - type CTL. These studies suggest that both TCR α/β - and γ/δ -type CTL may require antigenic peptides that are most likely derived from the BFA-sensitive, intracellular endogenous target proteins.     

Glucocorticoid-induced tumor necrosis factor receptor stimulation enhances the multifunctionality of adoptively transferred tumor antigen-specific CD8+ T cells with tumor regression

We have reported for the first time the significance of effector T-cell multifunctionality in antitumor immunity, suggesting that the appearance of multifunctional/polyfunctional tumor-specific CD8⁺ T cells in vivo is a critical determinant of the success of antitumor immunotherapy, and a strategy to induce multifunctionality in effector cells is required for the successful immunotherapy of hosts with progressing tumor. Glucocorticoid-induced tumor necrosis factor receptor (GITR) stimulation has been shown to enhance antitumor immune response. However, its functional impact on adoptively transferred T cells remains unclear. Here, we analyzed the impact of GITR stimulation in vivo on the functional profiles of adoptively transferred CD8⁺ T cells specific for murine fibrosarcoma CMS5. GITR stimulation was found to enhance multifunctionality (interferon (IFN)-γ and tumor necrosis factor (TNF)-α production and CD107a mobilization as a degranulation marker) in transferred cells at the single-cell level. These cells exhibited upregulated expression of CD25 in draining lymph nodes and increased infiltration in tumor. Mice that received T-cell therapy with GITR stimulation showed reduced Foxp3⁺CD4⁺ T cells among tumor infiltrating lymphocytes and increased in vivo cytotoxic T lymphocytes (CTL) activity even with progressing tumor, resulting in enhanced tumor regression. These data strengthen the idea that effector T-cell multifunctionality is a sensitive immune correlate for successful immunotherapy against malignancy and provide an immunological rationale for effective T-cell therapy combined with GITR stimulation. ( Cancer Sci 2009; 100: 1317–1325)     

Augmentation of Human Cytotoxic T Lymphocytes against Autologous Tumor by a Factor Released from Human Monocytic Leukemia Cell Line

A human acute monocytic leukemia cell line, THP-1, releases a factor which activates human cytotoxic (killer) T lymphocytes (CTL) against autologous tumor in vitro . The factor, named cytotoxic (killer) T cell activating factor (KAF), is an acidic protein of 70,000 to 100,000 dalton molecular size. Peripheral blood leukocytes from two patients, bearing epithelioid sarcoma or malignant schwannoma, were cultured for 7 days with individual autologous tumor to induce CTL directed to the corresponding tumor. Monocyte-depleted peripheral leukocytes generated lesser CTL activity than the monocyte-containing leukocyte population. However, the KAF was able to replace the monocyte function. The KAF acted at the CTL generation phase as well as the effector phase. The KAF-activated killer cells possessed CD4^-8⁺ surface phenotype. The CTL killed autologous tumor or other unrelated tumor cell lines only when they shared some of the HLA class I antigens. It was also demonstrated that the KAF does not activate killer cells without proper antigenic stimuli, because the KAF-augmented CTL possess specificity against autologous tumor or other HLA-A or -B matched tumor cell lines. The therapeutic applicability of human KAF for anti-tumor CTL therapy against autologous tumor is discussed.     

Adult T-cell leukemia/lymphoma cells from blood and skin tumors express cytotoxic T lymphocyte-associated antigen-4 and Foxp3 but lack suppressor activity toward autologous CD8+ T cells

Adult T cell leukemia/lymphoma (ATL) cells share the CD4⁺CD25⁺ phenotype with regulatory T (Treg) cells. However, it is still controversial whether ATL cells are Treg cells. The aim of the present study was to investigate the Treg nature of ATL cells obtained from peripheral blood and skin tumors in terms of their phenotype and function. By flow cytometry and immunohistochemistry, the expression of the Treg-associated molecule cytotoxic T lymphocyte-associated antigen (CTLA)-4 and Foxp3 was examined in freshly isolated circulating and skin-infiltrating tumor cells from 21 ATL patients with skin eruptions. The expression of CTLA-4 on freshly isolated circulating tumor cells was elevated in two of 15 patients, and Foxp3 was expressed intracytoplasmically at high levels in three of nine patients. In five of the patients examined, skin-infiltrating tumor cells bore variously elevated CTLA-4 with high Foxp3 expression. The potentiality of ATL cells as Treg cells was further addressed by stimulating ATL cells with anti-CD3/CD28 monoclonal antibodies and monitoring CTLA-4 expression. With the stimulation, even CTLA-4-low ATL cells expressed higher levels of CTLA-4 than normal CD4⁺CD25⁺ cells. To study function, ATL cells isolated from blood and skin tumors were tested for their ability to suppress the proliferation of autologous CD8⁺ T cells stimulated with allogeneic lymphocytes. Despite the expression of CTLA-4 and Foxp3, these tumors were incapable of suppressing the proliferation of autologous CD8⁺ T cells. ATL cells are phenotypically Treg cells in at least some patients, but lack immunoregulatory functions, at least toward CD8⁺ T cells. ( Cancer Sci 2008; 99: 98–106)     

Cytotoxic Activity of CD4+ T Cells against Autologous Tumor Cells

The ⁵¹Cr-release assay is mostly applied to detecting the cytotoxic activity of CD8⁺ T cells, and little is known about the activity of CD4⁺ T cells. Therefore, the correlation between the cytotoxic activity of CD4⁺ or CD8⁺ T cells and the incubation period with autologous tumor cells was analyzed by two methods. The incubation periods were 4 and 20 h (4 h and 20 h assay) for the ⁵¹Cr-release assay. Eight pairs of tumor cells and T cells were assayed. T cells were fractionated into CD4⁺ and CD8⁺ T cells by using magnetic beads and panning methods, and those cells were activated by culture with recombinant interleukin-2 and immobilized anti-CD3 monoclonal antibody. In 6 out of 8 cases, no cytotoxic activity of CD4⁺ T cells was detected by the 4 h assay, whereas cytotoxic activity was detected in all cases in the 20 h assay. The cytotoxic activities in 20 h assay of CD4⁺ T cells were increased 67-fold in comparison with the activities in 4 h assay (range: 5–197). In the case of CD8⁺ T cells, cytotoxic activities were detected in 6 out of 8 cases in the 4 h assay. The lytic unit ratio of CD4⁺ and CD8⁺ T cells was calculated as 1.5 in the 20 h assay (range: 0.2->7.2) versus 0.4 in the 4 h assay (range: < 0.1–1.3). Cytotoxic activities in colorimetric assay using Crystal Violet with a 24 h incubation were similar to those in the 20 h ⁵¹Cr-release assay in all eight cases. These results indicate that CD4⁺ T cells have cytotoxic activity as strong as that of CD8⁺ T cells towards autologous tumor cells.     

Natural Antigenic Peptides from Squamous Cell Carcinoma Recognized by Autologous HLA-DR8–restricted CD4+ T Cells

A large number of human tumor antigens recognized by CD8⁺ cytotoxic T lymphocytes (CTL) have been identified. Some of them have been employed in clinical trials and have achieved some objective responses. However, little is known about those that are recognized by CD4⁺ T cells, except for a very few that were identified from melanomas. Previously, we reported that an oral squamous cell carcinoma (SCC) cell line, OSC–20, was effectively lysed by HLA-DRB1·08032 (HLA-DRS)-restricted autologous CD4⁺ T cell line, TcOSC–20. In this study, we performed two steps of chromatographic purification of the tumor cell lysate in combination with mass spectrometry. We found one reverse-phase high-performance liquid chromatography (RP-HPLC) fraction that was effectively recognized by the T cells. We analyzed the fraction by nano-liquid chromatography/electrospray ionization ion trap mass spectrometry (LC/MS/MS) and found six representative ions. We could determine the primary amino acid sequence of each of the six ions. Three of them contained a potential HLA-DR8 binding motif, and TcOSC–20 showed a rather strong cytotoxic response to one of the synthetic pep tides, namely, amino acid residues 321–336 of human a-enolase. Thus, several gene products of squamous cancer cells are endogenously processed and may be presented on HLA class II molecules, so that they could constitute target molecules for autologous CD4⁺ T cells.     

An efficient method to prepare T cell receptor gene-transduced cytotoxic T lymphocytes type 1 applicable to tumor gene cell-therapy

Genes encoding 2C T cell receptor (TCR) α, β chains from H-2^b-re-stricted L^d-specific CD8⁺ cells were successfully transduced into polyclonally activated CD8⁺ cells by retroviral modification to generate antigen-specific cytotoxic T lymphocytes (CTL). Antigen-nonspecific CD8⁺ T cells polyclonally expanded in the presence of interleukin (IL)-2, Th1 cytokines (interferon (IFN)-γ and IL-12) and anti-IL-4 monoclonal antibody showed neither cytokine production nor cytotoxicity in response to L^d-expressing P815 tumor cells. However, 2C-TCR gene-modified CD8⁺ T cells exhibited both IFN-γ production and cytotoxicity in response to P815 tumor cells. The antitumor activity of TCR gene-modified Tc1 cells was also demonstrated in vivo by Winn's assay. Thus, we have developed an efficient method to induce TCR gene-modified antigen-specific Tc1 cells that exhibit antitumor activity both in vitro and in vivo . (Cancer Sci 2003; 94: 389–393)     

Histocompatibility Leukocyte Antigen-A2402-restricted Cytotoxic T Lymphocytes Recognizing Adenocarcinoma in Tumor-infiltrating Lymphocytes of Patients with Colon Cancer

To cast light on T cell-mediated specific immunity at the tumor site of colon cancer, we investigated whether interleukin-2 (IL-2)-activated tumor-infiltrating lymphocytes (TIL) from colon cancer show histocompatibility leukocyte antigen (HLA)-class I-restricted cytotoxicity against adenocarcinoma. IL 2-activated TIL from all four HLA-A24 patients examined lysed HLA-A2402+ adenocarcinomas, but not HLA-A2402 tumors. Those of two of the four cases also lysed HLA-A2402⁺ squamous cell carcinomas. CD8⁺ cytotoxic T lymphocyte (CTL) clones recognizing HLA-A2402⁺ adenocarcinomas were established from one CTL line. This CTL line produced IFN-γ upon recognition of an HLA-A2402^- adenocarcinoma transfected with HLA-A2402 cDNA. These results suggest the presence of HLA-A2402-restricted CTL recognizing adenocarcinoma at the tumor site of colon cancer. Furthermore, HLA-A31-restricted CTL activity was found in IL-2-activated TIL from one of two HLA-A31⁺ patients, suggesting the existence of HLA-class I-restricted CTL involving an allele other than A24     

Induction Mechanism of Human Blood CD8+ T Cell Proliferation and Cytotoxicity by Natural Killer Cell Stimulatory Factor (Interleukin-12)

Natural killer cell stimulatory factor (NKSF J IL-12) has been found to induce cytotoxic activity of human blood T cells. In the present study, the effect of NKSF on induction of cytotoxic CD8⁺ T cells in the presence or absence of monocytes was examined. Highly purified lymphocytes (>99%) and monocytes (>90%) were isolated hy centrifugal elutriation from peripheral blood of normal donors. Then, CD8⁺ cells were isolated with antibody-bound magnetic beads from purified lymphocytes. The cytotoxicity of CD8⁺ cells was measured by ⁵¹Cr release assay for 4 h. NKSF enhanced the proliferative response of CD8⁺ cells stimulated with suboptimal concentrations of interleukin-2 (IL-2), but rather inhibited their proliferative and cytotoxic responses on stimulation with an optimal concentration of IL-2. NKSF stimulated CD8⁺ cells to produce interferon 7 (IFNγ) irrespective of the presence of added IL-2, and this effect was augmented by co-cultivation with monocytes. Blood monocytes upregulated induction of cytotoxic CD8⁺ cells stimulated with NKSF alone, and this effect was abolished by addition of antibody against IFNγ, but not of antibody against tumor necrosis factor a. Induction of NKSF-inducible cytotoxic CD8⁺ cells was inhibited by addition of transforming growth factor β, but not of IL-4. These observations suggest that in situ induction of NKSF-stimulated cytotoxic CD8⁺ cells may be regulated by complex cytokine networks, depending on the participation of monocytes.     

Reduction of End-stage Malignant Glioma by Injection with Autologous Cytotoxic T Lymphocytes

Autologous cytotoxic T lymphocytes (CTL) against primary-cultured malignant gliomas were generated from peripheral blood mononuclear cells in vitro in 4 patients. Activities of the CTL were highly specific to the corresponding autologous glioma and were inhibited, in one patient, with antibodies against CD3, CD8 and MHC-class I molecules. When the CTL were injected 3 times into the primary-tumor-resected cavity via an Ommaya tube, reduction of the recurrent tumors with magnetic resonance imaging (MRI)-measured volumes exceeding 45 cm³ was observed in 3 patients. In a patient with glioblastoma multiforme (GBM), the tumor volume (estimated, 130 cm³) was rapidly reduced to 1/3, although re-recurrence of the tumor followed 40 days later. A slight but distinct rapid reduction of the tumor volume was observed in another GBM patient and in an anaplastic astrocytoma patient; essentially no change was observed in a further GBM patient. These results suggest that adoptive immunotherapy with autologous CTL will be clinically effective against end-stage malignant gliomas.     

Sequential Involvement of Two Distinct CD4+ Regulatory T Cells during the Course of Transplantable Tumor Growth and Protection from 3–Methylcholanthrene-induced Tumorigenesis by CD25–depletion

The involvement of two phenotypically different regulatory T cells in different stages of tumor growth was investigated. Treatment of BALB/c mice with anti-CD25 monoclonal antibody (mAb) (PC61), but not anti-CD4 mAb (GK1.5) before RL male 1 or Meth A inoculation caused tumor rejection. On the other hand, treatment of BALB/c mice with anti-CD4 mAb (GK1.5) but not anti-CD25 mAb (PC61) on day 6 after inoculation of the same tumors caused rejection. The findings suggest that CD4⁺CD25⁺ T cells downregulated the rejection response in the early stage of tumor growth. On the other hand, putative CD4⁺CD25⁻ T cells downregulated the tumor rejection response in the late stage. Both CD4⁺CD25⁺ and putative CD4⁺CD25-T cells appeared to inhibit the efficient generation of cytotoxic T lymphocytes (CTL). The present study also demonstrated that the treatment of BALB/c mice with anti-CD25 mAb (PC61) at 4 or 6 weeks after 3–methylcholanthrene (3–MC) inoculation retarded tumor occurrence and prolonged survival.     

Cytotoxicity of Histocompatibility Leukocyte Antigen–DR8–restricted CD4+ Killer T Cells against Human Autologous Squamous Cell Carcinoma

Although CD8⁺ killer T cells reacting against human autologous tumor cells have recently been studied in detail, little is known about the cytotoxic mechanism of CD4⁺ T cells against such tumor cells. In order to investigate this, we have established CD4⁺ cytotoxic T lymphocyte TcOSC–20 lines. TcOSC–20 showed selective cytotoxic activity against autologous OSC–20 cells, derived from a cancer of the tongue, in an HLA–DR–restricted fashion. HLA–DR8 (DRB1* 08032) is the only DR molecule expressed on OSC–20 cells, and anti–DRS monoclonal antibody could inhibit the Cytotoxicity, suggesting that HLA–DRB1^★ 08032 is the tumor rejection antigen–presenting moleculeto TcOSC–20. The Fas ligand was expressed on TcOSC–20 lines, and its expression was induced upon mixed lymphocyte–tumor cell culture of autologous peripheral blood lymphocytes. Furthermore, the Cytotoxicity of TcOSC–20 was inhibited by anti–Fas ligand antibody.These data imply that TcOSC–20 lines recognize the tumor antigenic peptide presented by HLA–DR8, and exert Cytotoxicity against autologous tumor cells via a Fas–mediated cytotoxic pathway.     

Bispecific Antibody-directed Antitumor Activity of Human CD4+ Helper/Killer T Cells Induced by Anti–CD3 Monoclonal Antibody plus Interleukin 2

Freshly isolated human CD4⁺ T cells can not respond to recombinant interlenkin 2 (rIL–2) because of their lack of p75 IL–2 receptor expression. However, we succeeded In inducing a marked proliferation of purified CD4⁺ T cells by activation with rIL–2 plus anti–CD3 monoclonal antibody (mAb) cross–linked to a plastic plate. The proliferated CD4⁺ T cells produced a significant amount of IL–2 upon stimulation with phorbol ester plus A23187. Interestingly, CD4⁺ T cells activated with anti–CD3 mAb plus rIL–2 revealed a strong cytotoxic activity against Fc receptor (FcR)–positive tumor cells in the presence of anti–CD3 mAb. Moreover, the CD4⁺ T cells could lyse FcR–negative glioma cells by targeting with bispecific mAb containing anti–CD3 mAb and anti–glioma mAb. Thus, we demonstrated that rIL–2 and immobilized anti–CD3 mAb allowed the rapid generation of human CD4⁺ helper/killer T cells, which may be useful for the development of a new adoptive tumor immunotherapy.