EBV-induced molecule 1 ligand chemokine (ELC/CCL19) promotes IFN-gamma-dependent antitumor responses in a lung cancer model

The antitumor efficacy of EBV-induced molecule 1 ligand CC chemokine (ELC/CCL19) was evaluated in a murine lung cancer model. The ability of ELC/CCL19 to chemoattract both dendritic cells and T lymphocytes formed the rationale for this study. Compared with diluent-treated tumor-bearing mice, intratumoral injection of recombinant ELC/CCL19 led to significant systemic reduction in tumor volumes (p < 0.01). ELC/CCL19-treated mice exhibited an increased influx of CD4 and CD8 T cell subsets as well as dendritic cells at the tumor sites. These cell infiltrates were accompanied by increases in IFN-gamma, MIG/CXCL9, IP-10/CXCL10, GM-CSF, and IL-12 but a concomitant decrease in the immunosuppressive molecules PGE(2) and TGFbeta. Transfer of T lymphocytes from ELC/CCL19 treated tumor-bearing mice conferred the antitumor therapeutic efficacy of ELC/CCL19 to naive mice. ELC/CCL19 treated tumor-bearing mice showed enhanced frequency of tumor specific T lymphocytes secreting IFN-gamma. In vivo depletion of IFN-gamma, MIG/CXCL9, or IP-10/CXCL10 significantly reduced the antitumor efficacy of ELC/CCL19. These findings provide a strong rationale for further evaluation of ELC/CCL19 in tumor immunity and its use in cancer immunotherapy.     

IFN-gamma mediates CD4+ T-cell loss and impairs secondary antitumor responses after successful initial immunotherapy

Protective cell-mediated immune responses in cancer are critically dependent on T-helper type 1 (T(H)1) cytokines such as interferon-gamma (IFN-gamma). We have previously shown that the combination of CD40 stimulation and interleukin-2 (IL-2) leads to synergistic antitumor responses in several models of advanced metastatic disease. We now report that after this treatment and other immunotherapy regimens, the CD4+ T-cell population, in contrast to CD8+ T cells, did not significantly increase but rather exhibited a substantial level of apoptosis that was dependent on IFN-gamma. Mice immunized with tumor cells and treated with an immunotherapy regimen that was initially protective were later unable to mount effective memory responses compared with immunized mice not receiving immunotherapy. Immunotherapy given to tumor-bearing Ifngr-/- mice resulted in restoration of secondary responses. Thus, although immunotherapeutic regimens inducing strong IFN-gamma responses can lead to successful early antitumor efficacy, they may also impair the development of durable antitumor responses.     

Blocking programmed death-1 ligand-PD-1 interactions by local gene therapy results in enhancement of antitumor effect of secondary lymphoid tissue chemokine

The negative signal provided by interactions of programmed death-1 (PD-1) and its ligands, costimulatory molecules PD-L1 (also B7-H1) and PD-L2 (also B7-DC), is involved in the mechanisms of tumor immune evasion. In this study, we found that this negative signal was also involved in immune evasion in tumor immunotherapy. When we used different doses of a constructed eukaryotic expression plasmid, pSLC, which expresses functional murine secondary lymphoid tissue chemokine (SLC, CCL21), to treat BALB/c mice inoculated with H22 murine hepatoma cells, the inhibitory effect was enhanced along with the increase of pSLC dosage. Unexpectedly, however, the best complete inhibition rate of tumor was reached when pSLC was used at the dosage of 50 microg but not 100 or 200 microg. RT-PCR and real-time PCR revealed that both PD-L1 and PD-L2 genes were expressed in tumor and vicinal muscle tissues of tumor-bearing mice and the expression level was significantly increased if a higher dosage of pSLC was administered. We then constructed a eukaryotic expression plasmid (pPD-1A) that expresses the extracellular domain of murine PD-1 (sPD-1). sPD-1 could bind PD-1 ligands, block PD-Ls-PD-1 interactions, and enhance the cytotoxicity of tumor-specific CTL. Local gene transfer by injection of pPD-1A mediated antitumor effect and improved SLC-mediated antitumor immunity. The combined gene therapy with SLC plus sPD-1 did not induce remarkable autoimmune manifestations. Our findings provide a potent method of improving the antitumor effects of SLC and possibly other immunotherapeutic methods by local blockade of negative costimulatory molecules.     

Tumor cell lysate-pulsed dendritic cells are more effective than TCR Id protein vaccines for active immunotherapy of T cell lymphoma

TCR Id protein conjugated to keyhole limpet hemocyanin (KLH) (TCR Id:KLH) and injected with a chemical adjuvant (QS-21) induces a protective, Id-specific immune response against the murine T cell lymphoma, C6VL. However, Id-based immunotherapy of C6VL has not demonstrated therapeutic efficacy in tumor-bearing mice. We report here that C6VL lysate-pulsed dendritic cells (C6VL-DC) vaccines display enhanced efficacy in both the prevention and the therapy of T cell lymphoma compared with TCR Id:KLH with QS-21 vaccines. C6VL-DC vaccines stimulated potent tumor-specific immunity that protected mice against lethal challenge with C6VL and significantly enhanced the survival of tumor-bearing mice. Tumor-specific proliferation and secretion of IFN-gamma indicative of a Th1-type immune response were observed upon ex vivo stimulation of vaccine-primed lymph node cells. Adoptive transfer of immune T cell-enriched lymphocytes was sufficient to protect naive recipients from lethal tumor challenge. Furthermore, CD8(+) T cells were absolutely required for tumor protection. Although C6VL-DC and control vaccines stimulated low levels of tumor-specific Ab production in mice, Ab levels did not correlate with the protective ability of the vaccine. Thus, tumor cell lysate-pulsed DC vaccines appear to be an effective approach to generate potent T cell-mediated immune responses against T cell malignancies without requiring identification of tumor-specific Ags or patient-specific Id protein expression.     

Phenotype and homing of CD4 tumor-specific T cells is modulated by tumor bulk

Technical difficulties in tracking endogenous CD4 T lymphocytes have limited the characterization of tumor-specific CD4 T cell responses. Using fluorescent MHC class II/peptide multimers, we defined the fate of endogenous Leishmania receptor for activated C kinase (LACK)-specific CD4 T cells in mice bearing LACK-expressing TS/A tumors. LACK-specific CD44(high)CD62L(low) CD4 T cells accumulated in the draining lymph nodes and had characteristics of effector cells, secreting IL-2 and IFN-gamma upon Ag restimulation. Increased frequencies of CD44(high)CD62L(low) LACK-experienced cells were also detected in the spleen, lung, liver, and tumor itself, but not in nondraining lymph nodes, where the cells maintained a naive phenotype. The absence of systemic redistribution of LACK-specific memory T cells correlated with the presence of tumor. Indeed, LACK-specific CD4 T cells with central memory features (IL-2(+)IFN-gamma(-)CD44(high)CD62L(high) cells) accumulated in all peripheral lymph nodes of mice immunized with LACK-pulsed dendritic cells and after tumor resection. Together, our data demonstrate that although tumor-specific CD4 effector T cells producing IFN-gamma are continuously generated in the presence of tumor, central memory CD4 T cells accumulate only after tumor resection. Thus, the continuous stimulation of tumor-specific CD4 T cells in tumor-bearing mice appears to hinder the systemic accumulation of central memory CD4 T lymphocytes.     

Local radiation therapy of B16 melanoma tumors increases the generation of tumor antigen-specific effector cells that traffic to the tumor

Immunotherapy of cancer is attractive because of its potential for specificity and limited side effects. The efficacy of this approach may be improved by providing adjuvant signals and an inflammatory environment for immune cell activation. We evaluated antitumor immune responses in mice after treatment of OVA-expressing B16-F0 tumors with single (15 Gy) or fractionated (5 x 3 Gy) doses of localized ionizing radiation. Irradiated mice had cells with greater capability to present tumor Ags and specific T cells that secreted IFN-gamma upon peptide stimulation within tumor-draining lymph nodes than nonirradiated mice. Immune activation in tumor-draining lymph nodes correlated with an increase in the number of CD45(+) cells infiltrating single dose irradiated tumors compared with nonirradiated mice. Similarly, irradiated mice had increased numbers of tumor-infiltrating lymphocytes that secreted IFN-gamma and lysed tumor cell targets. Peptide-specific IFN-gamma responses were directed against both the class I and class II MHC-restricted OVA peptides OVA(257-264) and OVA(323-339), respectively, as well as the endogenous class I MHC-restricted B16 tumor peptide tyrosinase-related protein 2(180-188). Adoptive transfer studies indicated that the increased numbers of tumor Ag-specific immune cells within irradiated tumors were most likely due to enhanced trafficking of these cells to the tumor site. Together these results suggest that localized radiation can increase both the generation of antitumor immune effector cells and their trafficking to the tumor site.     

IL-12 and IL-10 expression synergize to induce the immune-mediated eradication of established colon and mammary tumors and lung metastasis

Preclinical studies demonstrated that certain cytokines are potentially useful for the induction of antitumor immune responses. However, their administration in clinical settings was only marginally useful and evoked serious toxicity. In this study, we demonstrate that the combination of autologous inactivated tumor cells expressing IL-12 and IL-10 induced tumor remission in 50-70% of mice harboring large established colon or mammary tumors and spontaneous lung metastases, with the consequent establishment of an antitumor immune memory. Mice treatment with tumor cells expressing IL-12 was only marginally effective, while expression of IL-10 was not effective at all. Administration of the combined immunotherapy stimulated the recruitment of a strong inflammatory infiltrate that correlated with local, increased expression levels of the chemokines MIP-2, MCP-1, IFN-gamma-inducible protein-10, and TCA-3 and the overexpression of IFN-gamma, but not IL-4. The combined immunotherapy was also therapeutically effective on established lung metastases from both colon and mammary tumors. The antitumor effect of the combined immunotherapy was mainly dependent on CD8+ cells although CD4+ T cells also played a role. The production of IFN-gamma and IL-4 by spleen cells and the development of tumor-specific IgG1 and IgG2a Abs indicate that each cytokine stimulated its own Th pathway and that both arms were actively engaged in the antitumor effect. This study provides the first evidence of a synergistic antitumor effect of IL-12 and IL-10 suggesting that a Th1 and a Th2 cytokine can be effectively combined as a novel rational approach for cancer immunotherapy.     

Antitumor effects of the mouse chemokine 6Ckine/SLC through angiostatic and immunological mechanisms

Mouse 6Ckine/SLC (secondary lymphoid tissue chemokine) is a chemotactic factor for dendritic cells, T cells, and NK cells in vitro. In addition, mouse 6Ckine/SLC interacts with the chemokine receptor CXCR3, as do several chemokines with antiangiogenic properties. These dual properties of mouse 6Ckine/SLC were tested for the induction of an antitumor response by transducing the C26 colon carcinoma tumor cell line with a cDNA encoding mouse 6Ckine/SLC. The C26-6CK-transduced cells showed reduced tumorigenicity in immunocompetent or in nude mice. Part of this effect was likely due to angiostatic mechanisms as shown by immunohistochemistry and Matrigel assay. C26-6CK tumors were also heavily infiltrated with leukocytes, including granulocytes, dendritic cells, and CD8+ T cells. In vivo, anti-CD8 treatment increased the tumorigenicity of the C26-6CK tumor cells, and tumor-infiltrating CD8+ T cells had the phenotype of memory effector cells, suggesting the induction of cytotoxic tumor-specific T lymphocytes. On the other hand, anti-asialo-GM1 depletion also increased the tumorigenicity of C26-6CK cells, supporting the participation of NK cells. Finally, tumor-infiltrating dendritic cells had the phenotype and functional features of immature dendritic cells. Overall, these results suggest that mouse 6Ckine/SLC has strong antitumor effects by inducing both angiostatic, CD8+ T cell-mediated, and possibly NK-mediated tumor resistance mechanisms.     

Soluble expression of recombinant human secondary lymphoid chemokine (SLC) in E. coli and research on its in vitro and in vivo bioactivity

Secondary lymphoid tissue chemokine (SLC) is a CC chemokine that plays an important role in leukocytes homing to lymphoid tissues. The ability of SLC to co-localize both T cells and dendritic cells formed the rationale to evaluate its utility in cancer immunotherapy. The in vivo antitumor effect of murine SLC (mSLC) has been well documented, but little is known about that of human SLC (hSLC). To investigate the antitumor efficiency in vivo of hSLC, the hSLC gene was artificially synthesized and induced to express as a soluble form in Escherichia coli. After purification, the purity of the recombinant human SLC (rhSLC) protein was above 95% by SDS-PAGE analysis. The K(d) of rhSLC binding to peripheral blood lymphocytes (PBLs) was 0.2186 +/- 0.02675 microM as assessed by FACS, and the maximal chemotactic index of rhSLC was 9.49 at 100 nM as assessed by in vitro chemotaxis assay. Then genomic sequences of hSLC and mSLC, and of human CCR7 (hCCR7) and murine CCR7 (mCCR7), the receptor for SLC, were aligned. It was found that hSLC and mSLC share 70.72% identity and hCCR7 and mCCR7share 86.77% identity. Furthermore, we found that rhSLC could chemoattract murine peripheral blood mononuclear cells (PBMCs) in vitro. On the basis of these facts, immune competent mice inoculated with S180 sarcoma cells were chosen as an in vivo model. Intratumoral injections of rhSLC inhibited tumor growth and increased survival. These findings suggest that, despite its incapability to bind to either human or murine CXCR3, which is related to angiostasis, rhSLC can induce an antitumor response in vivo by another route. This report proves that rhSLC has a potent tumor-inhibition ability that makes it a promising candidate agent in cancer immunotherapy.     

Single administration of low dose cyclophosphamide augments the antitumor effect of dendritic cell vaccine

Single administration of low dose cyclophosphamide (CTX) was previously reported to enhance the antitumor efficacy of immunotherapies. To investigate the possible mechanisms for this effect, we examined whether a single administration of low dose CTX could augment the immunogenicity of dendritic cell (DC) vaccines. Fifty milligrams per kilogram body weight dose of CTX was administrated intraperitoneally to mice after B16 melanoma or C26 colon carcinoma tumor models were established, DC vaccine generated from mouse bone marrow and pulsed with B16 or C26 tumor cells lysates were vaccinated 4 days later. CTX treatment potentiated the antitumor effects of the DC vaccine, and increased the proportion of IFN-γ secreting lymphocytes in spleens. Furthermore, a significantly reduced proportion of CD4+CD25+FoxP3+ regulatory T (T_reg) cells was detected by flow cytometry in spleen lymphocytes from tumor-bearing mice treated with CTX. Thus, a single administration of low dose CTX could augment antitumor immune responses of DC vaccine by reducing the proportion of CD4+CD25+FoxP3+ T_reg cells in tumor-bearing mice. Our results suggested a possible mechanism of CTX-induced immunopotentiation and provided a strategy of immunotherapy combining a low dose CTX with DC vaccine. J.-Y. Liu and Y. Wu contributed equally to this work.     

Intratumoral injection of dendritic and irradiated glioma cells induces anti-tumor effects in a mouse brain tumor model

Malignant astrocytoma is the most common primary brain tumor in adults. The median survival of patients with malignant astrocytomas (high-grade astrocytomas) is about 1-2 years, despite aggressive treatment that includes surgical resection, radiotherapy and cytotoxic chemotherapy. Therefore, novel therapeutic approaches are needed to prolong survival. We investigated antitumor immunity conferred by the intratumoral injection of dendritic (DC) and irradiated glioma cells (IR-GC) in a mouse brain tumor model. Intratumorally injected DC migrated to the lymph nodes and elicited systemic immunity against autologous glioma cells. In a treatment model, intratumoral injection of DC and IR-GC prolonged the survival of brain tumor-bearing mice. Efficacy was reduced when studies were performed in mice depleted of CD8(+) T cells. Administration of DC or IR-GC alone had no effect on survival of brain tumor-bearing mice. CTL activity against glioma cells from immunized mice was also stimulated by coadministration of DC and IR-GC compared with the controls. These results support the therapeutic efficacy of intratumoral injection of DC and IR-GC.     

IL-27 mediates complete regression of orthotopic primary and metastatic murine neuroblastoma tumors: role for CD8+ T cells

We have shown previously that IFN-gamma-inducing cytokines such as IL-12 can mediate potent antitumor effects against murine solid tumors. IL-27 is a newly described IL-12-related cytokine that potentiates various aspects of T and/or NK cell function. We hypothesized that IL-27 might also mediate potent antitumor activity in vivo. TBJ neuroblastoma cells engineered to overexpress IL-27 demonstrated markedly delayed growth compared with control mice, and complete durable tumor regression was observed in >90% of mice bearing either s.c. or orthotopic intra-adrenal tumors, and 40% of mice bearing induced metastatic disease. The majority of mice cured of their original TBJ-IL-27 tumors were resistant to tumor rechallenge. Furthermore, TBJ-IL-27 tumors were heavily infiltrated by CD8(+) T cells, and draining lymph node-derived lymphocytes from mice bearing s.c. TBJ-IL-27 tumors are primed to proliferate more readily when cultured ex vivo with anti-CD3/anti-CD28 compared with lymphocytes from mice bearing control tumors, and to secrete higher levels of IFN-gamma. In addition, marked enhancement of local IFN-gamma gene expression and potent up-regulation of cell surface MHC class I expression are noted within TBJ-IL-27 tumors compared with control tumors. Functionally, these alterations occur in conjunction with the generation of tumor-specific CTL reactivity in mice bearing TBJ-IL-27 tumors, and the induction of tumor regression via mechanisms that are critically dependent on CD8(+), but not CD4(+) T cells or NK cells. Collectively, these studies suggest that IL-27 could be used therapeutically to potentiate the host antitumor immune response in patients with malignancy.     

Tumor rejection and immune memory elicited by locally released LEC chemokine are associated with an impressive recruitment of APCs, lymphocytes, and granulocytes

The human beta chemokine known as LEC (also called NCC-4, HCC-4, or LMC) displays chemotactic activity for monocytes and dendritic cells. The possibility that its local presence increases tumor immunogenicity is addressed in this paper. TSA parental cells (TSA-pc) are poorly immunogenic adenocarcinoma cells that grow progressively, kill both nu/nu and syngeneic BALB/c mice, and give rise to lung metastases. TSA cells engineered to release LEC (TSA-LEC) are still able to grow in nu/nu mice, but are promptly rejected and display a marginal metastatic phenotype in BALB/c mice. Rejection is associated with a marked T lymphocyte and granulocyte infiltration, along with extensive macrophage and dendritic cell recruitment. NK cells and CD4+ T lymphocytes are uninfluential in TSA-LEC cell rejection, whereas both CD8+ lymphocytes and polymorphonuclear leukocytes play a major role. An antitumor immune memory is established very quickly after rejection, since 6 days later 75% of BALB/c mice were already resistant to a TSA-pc challenge. Spleen cells from rejecting mice display specific cytotoxic activity against TSA-pc and secrete IFN-gamma and IL-2 when restimulated by TSA-pc. The ability of LEC to markedly improve recognition of poorly immunogenic cells by promoting APC-T cell cross-talk suggests that it could be an effective component of antitumor vaccines.     

Adoptive immunotherapy of breast cancer with lymph node cells primed by cryoablation of the primary tumor

Cryoablation of cancer leaves tumor-associated antigens intact in an inflammatory microenvironment that can stimulate a regional anti-tumor immune response. We examined whether cryoablated tumor draining lymph nodes (CTDLN) as adoptive immunotherapy may be an effective immunotherapeutic approach in the adjuvant treatment of breast cancer. BALB/c mice with MT-901 mammary adenocarcinoma tumors underwent cryoablation, resection or no treatment and tumor draining lymph nodes were harvested. Cryoablation resulted in only a mild increase in the absolute number of T-cells but a significant increase in the fraction of tumor-specific T-cells as evidenced on IFN-gamma release assay. FACS analysis demonstrated no significant relative shift in the proportion of CD4(+) or CD8(+) cells. The adoptive transfer of CTDLN resulted in a significant reduction of pulmonary metastases as compared to TDLN from either tumor-bearing mice or mice who underwent surgical excision. Cryoablation prior to surgical resection of breast cancer can be used as a method to generate effector T-cells for adjuvant adoptive cellular immunotherapy.     

Local injections of OK432 can help the infiltration of adoptively transferred CD8+ T cells into the tumor sites and synergistically induce the local production of Th1-type cytokines and CXC3 chemokines

The effect of local injections with streptococcal preparation OK432 on the antitumor effect induced by adoptive immunotherapy (AIT) was investigated. Draining lymph node cells on day 14 after B7-P815 inoculation were used for AIT after in vitro stimulation. AIT on days 7 and 10 showed no effect on the growth of s.c. established P815 mastocytoma, but local injections with OK432 into the tumor sites on days 3, 6 and 9 resulted in a moderate antitumor effect. On the other hand, the combination therapy significantly suppressed tumor growth, and the tumor-bearing mice survived longer than those receiving only one of the treatment modalities. The significant infiltration of CD4⁺ or CD8⁺ T cells and multiple necrosis in the tumor sites were observed only when the tumor-bearing mice were treated with the combination therapy. In addition, a transfer experiment using labeled effector cells revealed these infiltrated CD8⁺ T cells and CD4⁺ T cells to be derived from the donor and the host respectively. More importantly, the combination therapy clearly led to higher expression of the mRNA for Th1-type cytokines and CXC3 chemokines in the tumor sites than resulted from each of the treatment modalities alone. Collectively, these results indicate that local injections with OK432 can help the infiltration of adoptively transferred CD8⁺ T cells into the tumor sites and synergistically induce the local production of the Th1-type cytokines and CXC3 chemokines. Received: 3 April 2000 / Accepted: 5 May 2000     

Synergistic anti-tumor responses after administration of agonistic antibodies to CD40 and IL-2: coordination of dendritic and CD8+ cell responses

In cancer, the coordinate engagement of professional APC and Ag-specific cell-mediated effector cells may be vital for the induction of effective antitumor responses. We speculated that the enhanced differentiation and function of dendritic cells through CD40 engagement combined with IL-2 administration to stimulate T cell expansion would act coordinately to enhance the adaptive immune response against cancer. In mice bearing orthotopic metastatic renal cell carcinoma, only the combination of an agonist Ab to CD40 and IL-2, but neither agent administered alone, induced complete regression of metastatic tumor and specific immunity to subsequent rechallenge in the majority of treated mice. The combination of anti-CD40 and IL-2 resulted in significant increases in dendritic cell and CD8(+) T cell number in advanced tumor-bearing mice compared with either agent administered singly. The antitumor effects of anti-CD40 and IL-2 were found to be dependent on CD8(+) T cells, IFN-gamma, IL-12 p40, and Fas ligand. CD40 stimulation and IL-2 may therefore be of use to promote antitumor responses in advanced metastatic cancer.     

Role of regulator of G protein signaling 16 in inflammation-induced T lymphocyte migration and activation

Chemokine-induced T lymphocyte recruitment to the lung is critical for allergic inflammation, but chemokine signaling pathways are incompletely understood. Regulator of G protein signaling (RGS)16, a GTPase accelerator (GTPase-activating protein) for Galpha subunits, attenuates signaling by chemokine receptors in T lymphocytes, suggesting a role in the regulation of lymphocyte trafficking. To explore the role of RGS16 in T lymphocyte-dependent immune responses in a whole-organism model, we generated transgenic (Tg) mice expressing RGS16 in CD4(+) and CD8(+) cells. rgs16 Tg T lymphocytes migrated to CC chemokine ligand 21 or CC chemokine ligand 12 injection sites in the peritoneum, but not to CXC chemokine ligand 12. In a Th2-dependent model of allergic pulmonary inflammation, CD4(+) lymphocytes bearing CCR3, CCR5, and CXCR4 trafficked in reduced numbers to the lung after acute inhalation challenge with allergen (OVA). In contrast, spleens of sensitized and challenged Tg mice contained increased numbers of CD4(+)CCR3(+) cells producing more Th2-type cytokines (IL-4, IL-5, and IL-13), which were associated with increased airway hyperreactivity. Migration of Tg lymphocytes to the lung parenchyma after adoptive transfer was significantly reduced compared with wild-type lymphocytes. Naive lymphocytes displayed normal CCR3 and CXCR4 expression and cytokine responses, and compartmentation in secondary lymphoid organs was normal without allergen challenge. These results suggest that RGS16 may regulate T lymphocyte activation in response to inflammatory stimuli and migration induced by CXCR4, CCR3, and CCR5, but not CCR2 or CCR7.     

CD8-mediated type 1 antitumor responses selectively modulate endogenous differentiated and nondifferentiated T cell localization, activation, and function in progressive breast cancer

CD8 T cell-mediated immune responses fall into two distinct types based on effector cell-derived cytokine production. Type I CD8 T cells (Tc1) produce IFN-gamma, whereas type 2 cells (Tc2) secrete IL-4, IL-5, IL-10, and GM-CSF. Using a murine TCR transgenic T cell/breast tumor model, we show that adoptively transferred Ag-specific Tc1 cells are more effective in delaying mammary tumor growth and progression than that of functionally distinct Tc2 cells. Donor Tc1 cells administered 7 days posttumor challenge localized and persisted at sites of primary tumor growth with antitumor responses that were dependent, in part, on effector cell-derived IFN-gamma. Tc1-mediated responses markedly enhanced the appearance and local accumulation of highly differentiated (CD44(high)) CD4 and CD8 endogenous tumor-infiltrating T cells when compared with that of untreated tumor-bearing mice. Conversely, Tc1 cell transfer markedly delayed the appearance of corresponding nondifferentiated (CD44(low)) endogenous T cells. Such cells were acutely activated as defined by coexpression of surface markers associated with TCR engagement (CD69) and early T cell activation (CD25). Moreover, cellular response kinetics appeared to further correlate with the up-regulation of endogenous T cells producing the chemokine IFN-gamma-inducible protein-10 in vivo. This suggested that CD8-mediated type 1 antitumor responses cannot only promote accumulation of distinct endogenous CD4 and CD8 T cell subpopulations, but also facilitate and preferentially modulate their localization kinetics, persistence, states of activation/differentiation, and function within the primary tumor environment at various stages of tumor progression. These studies offer insight into potential mechanisms for enhancing T cell-based immunotherapy in breast cancer.     

The dendritic cell-specific chemokine,dendritic cell-derived CC chemokine 1, enhances protective cell-mediated immunity to murine malaria

Cell-mediated immunity plays a crucial role in the control of many infectious diseases, necessitating the need for adjuvants that can augment cellular immune responses elicited by vaccines. It is well established that protection against one such disease, malaria, requires strong CD8(+) T cell responses targeted against the liver stages of the causative agent, Plasmodium spp. In this report we show that the dendritic cell-specific chemokine, dendritic cell-derived CC chemokine 1 (DC-CK1), which is produced in humans and acts on naive lymphocytes, can enhance Ag-specific CD8(+) T cell responses when coadministered with either irradiated Plasmodium yoelii sporozoites or a recombinant adenovirus expressing the P. yoelii circumsporozoite protein in mice. We further show that these enhanced T cell responses result in increased protection to malaria in immunized mice challenged with live P. yoelii sporozoites, revealing an adjuvant activity for DC-CK1. DC-CK1 appears to act preferentially on naive mouse lymphocytes, and its adjuvant effect requires IL-12, but not IFN-gamma or CD40. Overall, our results show for the first time an in vivo role for DC-CK1 in the establishment of primary T cell responses and indicate the potential of this chemokine as an adjuvant for vaccines against malaria as well as other diseases in which cellular immune responses are important.     

Cutting edge: ectopic expression of the chemokine TCA4/SLC is sufficient to trigger lymphoid neogenesis

To test whether accumulation of naive lymphocytes is sufficient to trigger lymphoid development, we generated mice with islet expression of the chemokine TCA4/SLC. This chemokine is specific for naive lymphocytes and mature dendritic cells (DC) which express the CCR7 receptor. Islets initially developed accumulations of T cells with DC, with scattered B cells at the perimeter. These infiltrates consolidated into organized lymphoid tissue, with high endothelial venules and stromal reticulum. Infiltrate lymphocytes showed a naive CD44low CD25- CD69- phenotype, though half were CD62L negative. When backcrossed to RAG-1 knockout, DC were not recruited. Interestingly, islet lymphoid tissue developed in backcrosses to Ikaros knockout mice despite the absence of normal peripheral nodes. Our results indicate that TCA4/SLC can induce the development and organization of lymphoid tissue through diffential recruitment of T and B lymphocytes and secondary effects on stromal cell development.