Specific adoptive immunotherapy mediated by tumor-draining lymph node cells sequentially activated with anti-CD3 and IL-2.

Lymph nodes (LN) draining progressively growing tumors contain tumor-sensitized but not fully functional preeffector lymphocytes. These cells could acquire therapeutic efficacy and be expanded upon sequential culture with anti-CD3 mAb for 2 days followed by incubation in IL-2 for 3 days. Using the weakly immunogenic MCA 106 and MCA 205 murine sarcomas, we have further defined conditions of this anti-CD3/IL-2 activation with which preeffector cells differentiated into immune effector cells. In vitro activation and expansion of effector cells required sequential but independent stimulation with anti-CD3 and IL-2 because the simultaneous presence of both anti-CD3 and IL-2 at either stage did not enhance the efficacy of activation. Generation of effector cells by this two-stage activation was critically dependent on the optimal concentrations of anti-CD3 (1.0 microgram/ml) and IL-2 (2-10 U/ml). However, these conditions were not optimal for inducing the greatest cellular proliferation. In adoptive immunotherapy experiments, although the transfer of anti-CD3/IL-2-activated cells alone could mediate the regression of established metastases, the concomitant administration of IL-2 enhanced the in vivo activity of these cells. More importantly, tumor regression mediated by the anti-CD3/IL-2-activated cells was found to be immunologically specific. The specificity was determined by the tumor that stimulated the preeffector cell response. In spite of their in vivo antitumor effects, the anti-CD3/IL-2-activated tumor-draining LN cells did not exhibit detectable in vitro cytotoxicity against the tumor target in the 4-h 51Cr-release assay. In mice bearing progressive tumor, draining LN contained most preeffector cells. Some preeffector cells were also detected in the spleen whereas mesenteric LN did not demonstrate any reactivity. In kinetics studies, sensitization of preeffector cells in the draining LN occurred between 4 to 6 days after tumor inoculation. As the tumor progressed, the presence of preeffector cells declined gradually suggesting a tumor-induced suppression. These results define the conditions whereby tumor-draining LN cells could be stimulated, in the absence of tumor Ag, to develop into specific therapeutic effector cells. Our findings also raise the possibility of using similar approaches for isolating immune effector cells from cancer patients for adoptive immunotherapy.     

Effector phenotype and immunologic specificity of T-cell-mediated adoptive therapy for a murine tumor that lacks intrinsic immunogenicity

The MCA 102 sarcoma has been defined by a variety of immunologic studies as a tumor lacking intrinsic immunogenicity. Nevertheless, we have recently demonstrated the feasibility of generating therapeutically effective lymphocytes for adoptive immunotherapy of this tumor. Procedures to achieve this required in vivo priming of syngeneic mice to elicit preeffector cells followed by in vitro sensitization (IVS) with tumor cells in the presence of IL-2. By selective depletion of T cell subsets in vivo, we identified the involvement of both CD4+ (L3T4+) and CD8+ (Lyt-2+) T cells in mediating tumor regression. The CD4+ cells exerted their helper function via the secretion of IL-2 because antitumor effects abrogated by depletion of CD4+ cells could be reconstituted by exogenous IL-2. In order to elicit preeffector cells with reactivity against the MCA 102 tumor, we found that in vivo sensitization could be accomplished with either the MCA 102 or MCA 106 tumor but not with the MCA 101 or MCA 105 tumor. Analysis of specificity of tumor stimulation during IVS of MCA 102 tumor-primed preeffector cells demonstrated cross-reactivity between not only the MCA 102 and MCA 106 tumors but also the MCA 105 tumor whereas the MCA 101 tumor was ineffective. In adoptive immunotherapy, transfer of IVS cells generated from MCA 102 tumor-primed and stimulated lymph node cells was able to mediate reductions of pulmonary metastases established from the MCA 102, MCA 105, and MCA 106 tumors but not from the MCA 101 tumor. We conclude that regression of the MCA 102 tumor is probably mediated through T cell recognition of a set of common tumor-associated Ag shared by several other syngeneic tumors. Immunologically, the tumor-associated Ag are characteristically different from classical tumor-specific transplantation Ag (TSTA) because immunity to TSTA on the MCA 105 or MCA 106 tumor does not cross-react with the MCA 102 tumor. Thus, this study demonstrates that Ag other than TSTA on chemically induced tumors can serve as target molecules for T cell-mediated adoptive immunotherapy.     

Cross-presentation of tumor antigens to effector T cells is sufficient to mediate effective immunotherapy of established intracranial tumors

The systemic adoptive transfer of tumor-sensitized T cells, activated ex vivo, can eliminate established intracranial tumors. Regression of MHC class II negative MCA 205 fibrosarcomas occurs optimally following adoptive transfer of both CD4 and CD8 tumor-sensitized T cells, indicating an important function for tumor-infiltrating APC. Here, we demonstrate that during an effector response, indirect presentation of tumor Ags to transferred T cells is sufficient to mediate intracranial tumor regression. BALB/c --> CB6F1 (H-2bxd) bone marrow chimeras were challenged with the MCA 205 fibrosarcoma (H-2b). The tumor grew progressively in the H-2b-tolerant chimeras and stimulated an immune response in tumor-draining lymph nodes. Tumor-sensitized lymph node T cells were activated ex vivo with anti-CD3 and IL-2, then adoptively transferred to sublethally irradiated BALB/c or C57BL/6 recipients bearing established intracranial MCA 205 tumors. The transferred T cells eradicated MCA 205 tumors in BALB/c recipients and demonstrated tumor specificity, but had no therapeutic efficacy in the C57BL/6 recipients. These data establish that tumor-associated host cell constituents provide sufficient Ag presentation to drive effector T cell function in the complete absence of direct tumor recognition. This effector mechanism has an evident capacity to remain operative in circumstances of immune escape, where the tumor does not express the relevant MHC molecules, and may have importance even at times when direct CTL recognition also remains operative.     

Pre-existing tumor-sensitized T cells are essential for eradication of established tumors by IL-12 and cyclophosphamide plus IL-12.

The antitumor immune response activated by IL-12, especially by a combination of cyclophosphamide and IL-12 (Cy+IL-12), is clinically significant in certain experimental tumor models, in that a number of well-established (10-20 mm in diameter) s.c. tumors are completely eradicated. Furthermore, Cy+IL-12 treatment is also able to eradicate well-established grossly detectable experimental lung metastases and advanced ascites tumors. Despite the dramatic antitumor effects seen in some tumor models, Cy+IL-12 fails to induce regression of other established tumors. Characterization of tumor immunogenicity shows that all tumors responding to IL-12 and Cy+IL-12 treatments are immunogenic tumors, in that an antitumor immune response is detectable in tumor-bearing hosts upon tumor establishment. In contrast, none of the nonimmunogenic tumor responds to IL-12 and Cy+IL-12 treatments. Analysis of cellular requirements for successful tumor rejection through an adoptive cell transfer approach reveals that the presence of tumor-sensitized, but not naive, T cells is essential for tumor rejection by IL-12 and Cy+IL-12. Transfer of these tumor-sensitized T cells must be conducted before, but not after, IL-12 treatment in order for tumor rejection to occur. The requirement of sensitized T cells is also tumor specific. In mice bearing immunogenic tumors, the presence of pre-existing tumor-sensitized T cells is demonstrated by adoptive cell transfer experiments using purified spleen T cells from these mice. Results from our study show that Cy+IL-12-based immunotherapy of cancer may be highly effective and that pre-existing tumor-sensitized T cells are essential for the success of the therapy.     

Murine anti-CD3 monoclonal antibody induces potent cytolytic activity in both T and NK cell populations

Antibodies specific for the CD3 complex have the capacity to both stimulate and inhibit a variety of T cell functions. We show here that a monoclonal antibody to the epsilon chain of CD3 can induce efficient non-MHC-restricted cytolytic activity in murine lymphocytes with peak activity occurring after 48 hr of incubation. In a panel of targets, the anti-CD3-activated effectors lysed tumor cells but not normal lymphoblasts. Cytolysis was not dependent on the presence of the antibody in the cytolytic assay. Moderate to high cytolytic activity was elicited from lymph nodes, spleen, and thymus by anti-CD3 treatment in vitro, whereas only low activity was apparent in bone marrow. The precursors of anti-CD3-activated cells consisted largely of mature T cells, although a smaller component of immature T cells was also involved. Thus, separation of thymocytes based on adhesion to peanut agglutinin revealed that both positive (immature) and negative (mature) fractions could be activated, while cytotoxic pretreatment of spleen cells with an antibody (J11d) to immature T cells before anti-CD3 activation significantly decreased the resulting cytotoxicity. The majority of precursors in spleen were Thy 1+ and CD8+ and/or AGM1+. Antibody depletion studies showed that the effector cells have both a T and a NK component consisting of Thy 1+, CD5+, CD8+, CD4-, and AGM1- cells and Thy 1-, CD5-, CD8-, CD4-, and AGM1+ cells, respectively. The production of significant amounts of IL-2 and TNF in culture following anti-CD3 treatment, along with the synergistic effect of exogenously added IL-2, suggests that one or both of the effector cell types could be induced by lymphokines. The intraperitoneal administration of the anti-CD3 antibody induces cytolytic activity in vivo. Therefore, the direct activation of cytolysis by anti-CD3 antibody and the additional effects, both direct and synergistic, of lymphokines produced by the activated lymphocytes could conceivably provide a potent anti-tumor therapy.     

Further characterization of cytotoxic T cells generated by short-term culture of human peripheral blood lymphocytes with interleukin-2 and anti-CD3 mAb

 In this study we have specifically investigated the participation of T cells in the cytotoxic activity of peripheral blood lymphocytes (PBL) activated by interleukin-2 (IL-2, 50 U/ml) alone or in combination with an anti-CD3 mAb (BMA030, 10 ng/ml, IgG2a). Purified CD3⁺ T cells, incubated in the presence of the anti-CD3 mAb for 4 days, mediated a cytotoxic activity against HL60 and U937 tumor cell lines. Several findings suggested the involvement of a redirected-cytotoxicity phenomenon, since the lytic process was restricted to target cell lines bearing the high-affinity Fcγ receptor (FcγRI) and T lymphocytes stimulated by IL-2 alone did not lyse these cell lines. Furthermore, anti-CD3 mAb F(ab′)₂, anti-CD3 IgG1 (UCHT1), phytohemagglutinin or staphylococcal enterotoxin A did not induce a similar cytotoxic activity in T lymphocytes. The cytotoxic process occurred in the presence of a very low level of anti-CD3 antibodies (in the nanomolar range). The cytotoxic activity of T cells stimulated by IL-2 or by IL-2 + BMA030, against OVCAR-3 cells (MOv18⁺ ovarian tumor cell line), was also compared in the presence of a bispecific antibody (OC/TR, anti-CD3 × MOv18). The stimulation by IL-2 + BMA030 induced approximately a twofold higher cytotoxic activity than IL-2-activated T cells. This could be related to the state of activation of effector cells stimulated by IL-2 + BMA030, since the phenotypic analysis showed an increased proportion of T cells expressing several activation/differentiation markers (CD25, HLA-DR, CD45R0, adhesion molecules). These findings could be applied to the design of therapeutic protocols using anti-CD3 ×antitumoral bispecific antibodies. Received: 6 December 1995 / Accepted: 4 June 1996     

Antigen receptor-mediated anergy in resting T lymphocytes and T cell clones. Correlation with lymphokine secretion patterns.

The goal of these studies was to define the stimuli and factors that control the induction of anergy in unimmunized resting T lymphocytes. Initial experiments, aimed at establishing the system, showed that exposure of Th1 but not Th2 clones to immobilized anti-CD3 leads to a block in autocrine growth factor production and proliferation upon subsequent restimulation with Ag+APC. Anergy is not prevented by accessory cells, suggesting that this model of T cell tolerance may be due to receptor-mediated inhibitory signals, independent of costimulatory molecules. Culture of small (resting) unimmunized T lymphocytes with anti-CD3 +/- IL-2 induces unresponsiveness to restimulation with anti-CD3, but culture with anti-CD3+IL-4, which stimulates the differentiation of resting cells into IL-4 producers, does not induce anergy. Thus, IL-4-producing clones and bulk populations of IL-4-producing T cells are resistant to Ag receptor-mediated inhibitory stimuli. These results provide experimental models for studying the mechanisms of anergy in normal, unselected, mature T cells, and demonstrate fundamental similarities between cloned cell lines and unimmunized T lymphocytes in the induction of anergy.     

Characterization of the CD4+ and CD8+ tumor infiltrating lymphocytes propagated with bispecific monoclonal antibodies

To study the CD4+ and CD8+ tumor infiltrating lymphocytes (TIL) in the antitumor response, we propagated these subsets directly from tumor tissues with anti-CD3:anti-CD8 (CD3,8) and anti-CD3:anti-CD4 (CD3,4) bispecific mAb (BSMAB). CD3,8 BSMAB cause selective cytolysis of CD8+ lymphocytes by bridging the CD8 molecules of target lymphocytes to the CD3 molecular complex of cytolytic T lymphocytes with concurrent activation and proliferation of residual CD3+CD4+ T lymphocytes. Similarly, CD3,4 BSMAB cause selective lysis of CD4+ lymphocytes whereas concurrently activating the residual CD3+CD8+ T cells. Small tumor fragments from four malignant melanoma and three renal cell carcinoma patients were cultured in medium containing CD3,8 + IL-2, CD3,4 + IL-2, or IL-2 alone. CD3,8 led to selective propagation of the CD4+ TIL whereas CD3,4 led to selective propagation of the CD8+ TIL from each of the tumors. The phenotypes of the TIL subset cultures were generally stable when assayed over a 1 to 3 months period and after further expansion with anti-CD3 mAb or lectins. Specific 51Cr release of labeled target cells that were bridged to the CD3 molecular complexes of TIL suggested that both CD4+ and CD8+ TIL cultures have the capacity of mediating cytolysis via their Ti/CD3 TCR complexes. In addition, both CD4+ and CD8+ TIL cultures from most patients caused substantial (greater than 20%) lysis of the NK-sensitive K562 cell line. The majority of CD4+ but not CD8+ TIL cultures also produced substantial lysis of the NK-resistant Daudi cell line. Lysis of the autologous tumor by the TIL subsets was assessed in two patients with malignant melanoma. The CD8+ TIL from one tumor demonstrated cytotoxic activity against the autologous tumor but negligible lysis of allogeneic melanoma targets. In conclusion, immunocompetent CD4+ and CD8+ TIL subsets can be isolated and expanded directly from small tumor fragments of malignant melanoma and renal cell carcinoma using BSMAB. The resultant TIL subsets can be further expanded for detailed studies or for adoptive immunotherapy.     

CD28, TNF receptor,and IL-12 are critical for CD4-independent cross-priming of therapeutic antitumor CD8+ T cells

Previously, we have shown that priming of therapeutic CD8(+) T cells in tumor vaccine-draining lymph nodes of mice vaccinated with GM-CSF secreting B16BL6 melanoma cells occurs independent of CD4 T cell help. In this study, we examined the contribution of the major costimulatory molecules, CD40 ligand (CD40L), CD80, and CD86, in the priming of CD8(+) T cells. Priming of therapeutic CD8(+) T cells by a GM-CSF-transduced tumor vaccine did not require CD40 and CD40L interactions, as therapeutic T cells could be generated from mice injected with anti-CD40L Ab and from CD40L knockout mice. However, costimulation via either CD80 or CD86 was required, as therapeutic T cells could be generated from mice injected with either anti-CD80 or anti-CD86 Ab alone, but administration of both Abs completely inhibited the priming of therapeutic T cells. Blocking experiments also identified that priming of therapeutic T cells in MHC class II-deficient mice required TNFR and IL-12 signaling, but signaling through CD40, lymphotoxin-betaR, or receptor activator of NF-kappaB was not essential. Thus, cross-priming of therapeutic CD8(+) T cells by a tumor vaccine transduced with GM-CSF requires TNFR, IL-12, and CD28 signaling.     

Enhancement of T helper2 response in the absence of interleukin (IL-)6; an inhibition of IL-4-mediated T helper2 cell differentiation by IL-6

Functional roles of interleukin (IL-)6 in T cell response were investigated. Mice deficient in IL-6 and wild mice were immunized with antigens (myelin oligodendrocyte glycoprotein or methylated BSA) and production of IL-4 and interferon (IFN)-gamma by regional lymph nodes was measured. IL-6 deficiency led to an enhancement of IL-4 and an inhibition of IFN-gamma production. Moreover, polyclonal stimulation of spleen T cells from unimmunized IL-6-deficient mice with anti-CD3 plus anti-CD28 antibodies (Abs) demonstrated an enhancement of T helper (Th)(2)responses. The presence of IL-6, however, augmented IL-4 production but it inhibited IFN-gamma expression by spleen T cells in response to polyclonal stimulation and by antigen-primed spleen T cells in response to re-challenge with the antigen. In contrast, the induction of spleen CD4-positive T cells into Th(2)cells in vitro by the anti-CD3 plus IL-4 was completely suppressed by exogenously added IL-6, whereas Th(1)differentiation of T cells by the anti-CD3 plus IL-12 was not inhibited by the presence of IL-6. Thus, these results indicate that IL-6 physiologically could modulate qualitative T cell response and suggest that it augments Th(1)responses partly through its inhibitory capability of IL-4-induced Th(2)differentiation of naive T cells.     

Frequency analysis of lymphokine-secreting CD4+ and CD8+ T cells activated in a graft-versus-host reaction

Lymphokine secretion by in vivo-activated T cells was analyzed at the population and single-cell levels in lymphocytes from mice undergoing an acute allogeneic graft-vs-host reaction (GVHR). Three observations were made. First, constitutive lymphokine production by these cells was very low but could be dramatically up-regulated by TCR ligation. Thus, even when harvested at the peak of the GVHR, fewer than 0.1% of lymphocytes secreted detectable granulocyte-macrophage (GM)-CSF, IFN-gamma, or IL-3 in the first 24 h in vitro, and average production of these lymphokines in bulk cultures was less than 10(-5) U/cell. However, when cultured for 24 h with anti-CD3 antibody under conditions which activated less than 0.1% of normal cells, about 30% of GVHR T cells secreted GM-CSF, IFN-gamma, and/or IL-3, and average production levels were increased by 10(3)- to 10(4)-fold. Together with evidence that host alloantigen-induced lymphokine secretion was 10 to 100 times lower than the anti-CD3 response, these data suggest that physiologic lymphokine synthesis by most T cells is low (less than 10(-18) mol of IL-3 per cell) but can be raised above the threshold of detection by TCR cross-linking. Second, individual GVHR lymphocytes varied markedly in their total and relative production of different lymphokines in response to anti-CD3 stimulation, with some cells secreting IL-3 alone, some secreting IL-3 accompanied by other lymphokines (GM-CSF and/or IFN-gamma), and some secreting other lymphokines without detectable IL-3. Finally, both CD4+ and CD8+ T cells from GVHR mice responded to anti-CD3 antibody by secreting IL-3 and other lymphokines: purified CD4+ cells contained an average of 16% and CD8+ cells an average of 10% anti-CD3-inducible lymphokine-secreting cells. By contrast, only 2 to 3% of cells of either subset formed clones in cultures with host allogeneic cells and IL-2, suggesting that clonogenic alloreactive cells were a minority of the T cells activated in the GVHR.     

Lysis of fresh solid tumor targets in the presence of Con A is mediated primarily by Leu 7+ peripheral blood T lymphocytes: blocking by the anti-CD3 monoclonal antibody and comparison with recombinant interleukin 2-induced lysis by natural killer cells

We investigated the lysis of fresh human solid tumor cells by peripheral blood T lymphocytes in the presence of lectins and anti-CD3 monoclonal antibodies (mAb). Addition of certain lectins (Con A, PHA, or WGA) directly into the 4-hr 51Cr-release assay caused significant lysis of (P less than 0.001) noncultured solid tumor targets by enriched populations of granular lymphocytes (GL). Significant levels (P at least less than 0.001) of Con A- or PHA-dependent solid tumor lysis by GL-enriched lymphocytes were observed in 32 of 39 donors (82%) and 14 of 20 donors (70%), respectively. In contrast, the addition of other lectins (PNA, PWM, or LPS) or anti-CD3 mAb did not cause cytotoxicity. The levels of Con A-dependent lysis were comparable to those of interleukin 2 (IL-2)-induced lysis by Leu 11b+ natural killer (NK) cells. The presence of lectins at the effector phase, but not of recombinant IL-2 (rIL-2), was required for the lysis of solid tumor targets. Both Con A-dependent and rIL-2-induced lysis were totally inhibited by treatment of the effector cells with the lysosomotropic agent L-leucine methyl ester (LeuOMe). Effector cells responsible for Con A-dependent lysis of solid tumors expressed T3 (CD3), T8 (CD8), and Leu 7 antigens, but lacked T4 (CD4) and Leu 11 (CD16) antigens as determined by both negative and positive cell selection studies. Con A-dependent lysis was inhibited at the effector phase by anti-CD3 (OKT3 or anti-Leu 4) or anti-CD2 (OKT11) mAb. On the basis of their phenotype (Leu 7+ CD3+ CD8+ CD16-), we hypothesize that these effector cells may contain a population of cytotoxic T cells (CTL) generated in vivo against autologous modified cells that can lyse fresh solid tumor target cells under conditions where the recognition requirements for the CTL are bypassed by lectin approximation.     

CD8+ T cells can be primed in vitro to produce IL-4.

IL-4 production by T lymphocytes from naive mice in response to stimulation by plate-bound anti-CD3 is concentrated among CD4+ T cells. In vitro stimulation of lymph node T cells with anti-CD3 plus IL-2 and IL-4 strikingly increases the frequency of cells that produce IL-4 in response to subsequent stimulation with anti-CD3 plus IL-2. Separation of these primed cell populations into CD4+ and CD8+ T cell by cell sorting reveals that the frequency of IL-4-producing cells in both population is similar. Verification that CD8+ T cells produce IL-4 is provided by the capacity of anti-IL-4 mAb to inhibit the response of the indicator cell line to the growth factor produced by the primed cells and by detection of IL-4 by an IL-4-specific ELISA. The in vitro "priming" of CD8+ T cells to produce IL-4 is not dependent on the presence of CD4+ T cells because highly purified CD8+ T cells can be stimulated to develop into cells capable of producing IL-4 by culture with plate-bound anti-CD3 plus IL-2 and IL-4.     

T cells from tumor-immune mice nonspecifically expanded in vitro with anti-CD3 plus IL-2 retain specific function in vitro and can eradicate disseminated leukemia in vivo.

The therapeutic efficacy of adoptive immunotherapy of cancer has been shown to positively correlate with the dose of tumor-immune T cells transferred. Therefore, the success of this therapy is critically dependent on the ability to procure large numbers of functionally active T cells. Previous studies in animal models have shown that the limited therapeutic efficacy of a small number of immune T cells can be greatly enhanced by expansion of T cells in vitro to greater numbers before transfer in vivo. Optimal regimens for T cell expansion in vitro have generally employed the use of intermittent stimulation of the TCR with specific Ag followed by exogenous IL-2. The use of IL-2 alone does not provide for requisite episodic up-regulation of IL-2R. Stimulation of the invariant CD3 portion of the TCR/CD3 complex with antibody to CD3 (anti-CD3) represents an alternative method of up-regulating IL-2R and has been used to nonspecifically induce the growth of Ag-specific T cell lines and clones long-term in vitro with maintenance of function and specificity. The current study examined whether resting T cell populations containing small numbers of memory tumor-specific T cells could be rendered more effective in tumor therapy by nonspecific expansion in vitro with anti-CD3 plus IL-2. Spleens from C57BL/6 mice previously immunized to FBL-3, a syngeneic virus-induced leukemia, were nonspecifically stimulated with anti-CD3 plus IL-2. The resultant T cells were expanded in number, were nonlytic to FBL-3 but retained the ability to become lytic upon specific stimulation by FBL-3, and were effective in specific tumor therapy. The Ag-specific anti-tumor immune function declined on a per cell basis after each cycle of anti-CD3-induced T cell expansion. However, the approach resulted in a substantial increase in total T cell number and an overall net increase in the function of the effector T cell population. Thus, stimulation of tumor-immune T cell populations with anti-CD3 plus IL-2 represents a nonspecific method for expanding the number of specific effector T cells for cancer therapy.     

Generation propagation, and targeting of human CD4+ helper/killer T cells induced by anti-CD3 monoclonal antibody plus recombinant IL-2. An efficient strategy for adoptive tumor immunotherapy.

We developed a culture system for the rapid generation of CD4+ T cells that have both helper and killer functions. CD4+ T cells isolated from human PBL did not proliferate or develop significant cytotoxicity when treated with rIL-2 because of the lack of p75 IL-2R expression. However, culture of isolated CD4+ T cells with immobilized anti-CD3 mAb plus rIL-2 resulted in a marked proliferation (500-fold increase in 14 days) of CD4+ T cells. The proliferating CD4+ T cells produced IL-2 (92 U/ml) and showed strong cytotoxicity against OKT3 hybridoma cells and Daudi, K562, and U937 tumor cells in an anti-CD3 mAb-dependent manner. The CD4+ T cells contained significant amounts of cytolytic granule-related proteins such as serine esterase and perforin. Activated CD4+ helper/killer cells can be generated from both healthy donors and tumor patients and can be propagated in vitro for 14 to 35 days by biweekly restimulation with immobilized anti-CD3 mAb plus rIL-2. This culture yielded about 20,000-fold increase in cell number after a 21-day culture. Bispecific antibody containing anti-CD3 and anti-glioma Fab components enhanced the cytotoxicity of activated CD4+ helper/killer cells against IMR32 glioma cells. Moreover, the activated CD4+ helper/killer cells showed both helper and antitumor activity in vivo and prevented growth of anti-CD3 hybridoma cells in nude mice whether or not IL-2 was administered. These results indicate that anti-CD3 mAb plus IL-2-activated CD4+ helper/killer cells may provide an effective strategy for adoptive tumor immunotherapy of cancer.     

CD40 ligand promotes priming of fully potent antitumor CD4(+) T cells in draining lymph nodes in the presence of apoptotic tumor cells.

The presence or absence of CD4(+) T cell help can determine the direction of adaptive immune responses toward either cross-priming or cross-tolerance. It has been demonstrated that interactions of CD40-CD40 ligand can replace CD4(+) T cell help and enable dendritic cells to prime cytotoxic T cells. Here, we demonstrate that antitumor reactivity induced in regional lymph nodes (LNs) by s.c. injection of CD40 ligand (CD40L)-transduced tumor (MCA205 CD40L) showed far superior therapeutic efficacy against established brain tumors of a weakly immunogenic fibrosarcoma, MCA205, when adoptively transferred. Coinjection of apoptotic, but not necrotic parental tumor cells with CD40L-expressing tumor cells caused a strong synergistic induction of antitumor reactivity in tumor-draining LNs. Freshly isolated T cells from LNs immunized with apoptotic parental tumor cells and MCA205 CD40L were capable of mediating regression of the parental tumor in vivo. In contrast, T cells derived from LNs immunized without MCA205 CD40L required ex vivo anti-CD3/IL-2 activation to elicit therapeutic activity. On anti-CD3/IL-2 activation, cells from LNs immunized with MCA205 CD40L exhibited superior per cell antitumor reactivity. An in vitro depletion study revealed that either CD4(+) or CD8(+) T cells could mediate therapeutic efficacy but that the antitumor efficacy mediated by CD4(+) T cells was far superior. Cytosolic flow cytometric analyses indicated that priming of CD4(+) cells in LNs draining CD40L-expressing tumors was polarized to the Th1 type. This is the first report that fully potent antitumor CD4(+) T cell priming was promoted by s.c. injection of CD40L-transduced tumor in the presence of apoptotic tumor cells.     

Successful adoptive immunotherapy of murine poorly immunogenic tumor with specific effector cells generated from gene-modified tumor-primed lymph node cells

We previously reported that cytokine gene transfer into weakly immunogenic tumor cells could enhance the generation of precursor cells of tumor-reactive T cells and subsequently augment antitumor efficacy of adoptive immunotherapy. We investigated whether such potent antitumor effector T cells could be generated from mice bearing poorly immunogenic tumors. In contrast to similarly modified weakly immunogenic tumors, MCA102 cells, which are chemically induced poorly immunogenic fibrosarcoma cells transfected with cDNA for IL-2, IL-4, IL-6, IFN-gamma, failed to augment the host immune reaction. Because priming of antitumor effector T cells in vivo requires two important signals provided by tumor-associated Ags and costimulatory molecules, these tumor cells were cotransfected with a B7-1 cDNA. Transfection of both IFN-gamma and B7-1 (MCA102/B7-1/IFN-gamma) resulted in regression of s.c. tumors, while tumor transfected with other combinations of cytokine and B7-1 showed progressive growth. Cotransfection of IFN-gamma and B7-1 into other poorly immunogenic tumor B16 and LLC cells also resulted in the regression of s.c. tumors. Cells derived from lymph nodes draining MCA102/B7-1/IFN-gamma tumors showed potent antitumor efficacy, eradicating established pulmonary metastases, but this effect was not seen with parental tumors. This mechanism of enhanced antitumor efficacy was further investigated, and T cells with down-regulated L-selectin expression, which constituted all the in vivo antitumor reactivity, were significantly increased in lymph nodes draining MCA102/B7-1/IFN-gamma tumors. These T cells developed into potent antitumor effector cells after in vitro activation with anti-CD3/IL-2. The strategy presented here may provide a basis for developing potent immunotherapy for human cancers.     

Human natural killer cell adhesion molecules. Differential expression after activation and participation in cytolysis.

Cell adhesion molecules (CAM) participate in interactions between lymphocytes, accessory cells, and target cells that are critical in the generation of effective immune responses. To characterize the involvement of CAM in NK and lymphokine activated killer (LAK) activities, we examined the expression of several CAM by freshly isolated human NK cells and by NK cells activated in vitro with IL-2, and compared this to CAM expression by T lymphocytes under similar conditions. Freshly isolated human NK cells were uniformly LFA-3 (CD58)+ and expressed two to three-fold higher surface levels of LFA-1 (CD11a/CD18) than resting T lymphocytes. More NK cells than T cells also expressed phenotypically detectable levels of intercellular adhesion molecule-1 (CD54). After in vitro incubation with IL-2, human NK cells demonstrated four- to sixfold increases in surface levels of CD11a/CD18, CD2, CD54, CD58, and the NK cell-associated Ag NKH-1 (CD56). Furthermore, essentially all NK cells became CD54+ within 3 days of exposure to IL-2. T cells did not demonstrate comparable up-regulation of CAM after incubation with IL-2. Increases in NK cell CAM expression were associated with enhanced formation of E:T cell conjugates, enhanced killing of NK-sensitive targets, and the induction of cytotoxicity for previously NK-resistant targets (LAK activity). The LAK activity induced by exogenous IL-2 could be partially inhibited by anti-CD2, anti-CD11a, or anti-CD54 antibodies and almost completely abrogated by anti-CD2 and anti-CD11a in combination. These studies suggest that CAM play a central role in the regulation of NK cytolysis, and that changes in CAM expression may alter the target cell specificity of activated NK effectors.     

Anti-CD3 scFv-B7.1 fusion protein expressed on the surface of HeLa cells provokes potent T-lymphocyte activation and cytotoxicity.

The targeting of tumor cells by cytotoxic T lymphocytes is a promising strategy for biotherapy, but T cells require 2 signals via the T-cell receptor - CD3 complex and CD28 molecules for activation. To bridge the gap between cytotoxic T lymphocytes and tumor cells, our objective in this study was to describe the construction and the cell surface-anchored expression of a fusion protein, anti-CD3 scFv-B7.1, derived from inserting a fusion gene encoding anti-CD3 scFv and the extra-cellular domain of B7.1 fused by the splicing by overlap extension method into a mammalian expression vector, pDisplay. Transfection of the recombinant vector by electroporation into HeLa cells resulted in the production of protein migrating at approximately 57 kDa under reducing conditions. The expressed fusion protein could bind to T lymphocytes and induce strong T-cell activation. Meanwhile, a potent cytotoxicity was induced in the mixed culture of T-cell-modified tumor cells in a 96 h methyl-thiazolyl-diphenyl tetrazolium bromide assay. Our results indicate that this bifunctional protein, through activating T lymphocytes to lyse homologous human carcinomas, may be of potential value for T-cell-based immunotherapeutical treatment protocols in vivo.     

IL-4 production by T cells from naive donors. IL-2 is required for IL-4 production

Utilizing a sensitive and selective assay for IL-4, it was shown that lymph node T cells from naive mice could produce small amounts of this lymphokine in response to anti-CD3 antibodies adsorbed to culture dishes. The capacity of these cells to produce IL-4 in response to plate-bound anti-CD3 was substantially enhanced by the addition of IL-2 to the culture and was strikingly inhibited by monoclonal anti-IL-2 antibody. Thus, IL-2 appears to be essential for IL-4 production by anti-CD3 antibody-stimulated T cells from naive mice. The effect of IL-2 was not mediated either by preferential proliferation or survival of precursors of IL-4 producing cells, indicating that IL-2 regulates T cell production of IL-4. IL-4 producing capacity of T cells from naive mice was found mainly among CD4+ T cells. Large T cells produced much more IL-4, on a per cell basis, than did small T cells. In contrast, small T cells appeared to be equal or superior to large T cells in producing IL-2. The superiority of large T cells in IL-4-producing capacity was not accounted for by a lack of an accessory cell population from the small T cells as addition of large spleen cells depleted of both B and T cells did not enhance IL-4 production by small lymph node T cells. These results suggest that the bulk of IL-4 production by T cell populations, from normal mice, in response to anti-CD3 depends upon cells that are already activated and that IL-2 is required for such production.