Cyclophosphamide treatment induces rejection of established P815 mastocytoma by enhancing CD4 priming and intratumoral infiltration of P1E/H‐2Kd‐specific CD8+ T cells

There is increasing evidence that the effect of chemotherapy on tumor growth is not cell autonomous but relies on the immune system. The objective of this study was therefore to decipher the cellular and molecular mechanisms underlying the role of innate and adaptive immunity in chemotherapy‐induced tumor rejection. Treatment of DBA/2 mice bearing P815 mastocytoma with cyclophosphamide induced rejection and long‐term protection in a CD4‐ and CD8‐dependent manner. A population of inflammatory‐type dendritic cells was dramatically expanded in the lymph nodes of mice that rejected the tumor and correlated with CD4‐dependent infiltration, in tumor bed, of tumor‐specific CD8⁺ T lymphocytes. Our data point to a major role of CD4⁺ T cells in inducing chemokine expression in the tumor, provoking migration of tumor‐specific CXCR3⁺ CD8⁺ T lymphocytes. Importantly, the analysis of CD8⁺ T cells specific to P1A/H‐2L^d and P1E/H‐2K^d revealed that cyclophosphamide altered the P815‐specific CD8 T repertoire by amplifying the response specific to the mutated P1E antigen.     

Regulatory CD8+ T cells control thyrotropin receptor-specific CD4+ clones in healthy subjects

One of the mechanisms ensuring immunological unresponsiveness or tolerance depends on the action of CD8(+) lymphocytes. In this paper, we report that, in healthy subjects, a subset of CD8(+)CD28(-) T cells suppresses the specific response to TSH receptor (TSHR) of CD4(+) clones. Suppression was highly specific, required cell-cell interaction, and was not mediated by cytotoxicity. Co-incubation of CD8(+) and CD4(+) clones, followed by the removal of the CD8(+) cells from the cultures before testing CD4(+) responsiveness to TSHR, demonstrated that CD4(+) cells were anergic since they showed low response to the antigen and a significant impairment of IL-2 production. In CD8-mediated anergy induction, the T-cell receptor (TCR) on both CD4(+) and CD8(+) cells seems to play a role. Our results indicate that one of the mechanisms ensuring peripheral tolerance involve CD8(+)CD28(-) cells. A disregulation in the control of autoreactive clones by this subset might be important for the onset of autoimmune thyroid diseases.     

CD4+ T cells support polyfunctionality of cytotoxic CD8+ T cells with memory potential in immunological control of tumor

Polyfunctionality/multifunctionality of effector T cells at the single cell level has been shown as an important parameter to predict the quality of T cell response and immunological control of infectious disease and malignancy. However, the fate of polyfunctional CD8⁺ CTLs and the factors that control the polyfunctionality of T cells remain largely unknown. Here we show that the acquisition of polyfunctionality on the initial stimulation is a sensitive immune correlate of CTL survival and memory formation. CD8⁺ T cells with high polyfunctionality, assessed with γ‐interferon and tumor necrosis factor‐α production and surface mobilization of the degranulation marker CD107a, showed enhanced Bcl‐2 expression, low apoptosis, and increased CD127^highKLRG1^low memory precursor phenotype. Consistent with these observations, CD8⁺ T cells were found to acquire high frequency of cells with polyfunctionality when stimulated in conditions known to enhance memory formation, such as the presence of CD4⁺ T cells, interleukin (IL)‐2, or IL‐21. Utilizing T‐cell receptor (TCR) transgenic mouse‐derived CD8⁺ T cells that express a TCR specific for a tumor‐derived neoantigen, we showed that polyfunctional tumor‐specific CTLs generated in the presence of CD4⁺ T cells showed long persistence in vivo and induced enhanced tumor regression when adoptively transferred into mice with progressing tumor. Acquisition of polyfunctionality thus impacts CTL survival and memory formation associated with immunological control of tumor.     

CD4+CD25+调节性T细胞与CD4+T、CD8+T细胞在结直肠癌组织中的分布

 目的 分析CD4+CD25+ FOXP3+调节性T细胞（Treg）与CD4+T、CD8+T在结直肠癌（colorectal carcinoma, CRC）组织中的分布及其与临床病理特征之间的关系。方法 收集42例CRC新鲜手术标本,应用冰冻切片、免疫组织化学SP法检测肿瘤组织和癌旁组织中FOXP3+、CD4+T和CD8+T阳性细胞数。结果 CRC患者肿瘤组织中FOXP3表达水平显著升高,与癌旁组织相比差异有统计学意义（P<0.01）;中低分化组Treg细胞数明显高于高分化组（P<0.01）;淋巴结转移组Treg细胞数明显高于无淋巴结转移组（P<0.05）;癌巢内CD4+、CD8+T细胞数及CD4+/CD8+值显著低于间质（P<0.01）;Ⅲ+Ⅳ期、淋巴结转移组癌巢内CD4+/CD8+比值显著低于Ⅰ+Ⅱ期及无淋巴结转移组（P<0.05）;CRC中Treg数量与癌巢内CD4+/CD8+比值显著负相关（r=-0.605, P<0.01）。结论 CRC的发生发展可能与其癌组织局部微环境中Treg数量变化相关,肿瘤局部Treg数量的增多与T淋巴细胞亚群比例失调可能成为肿瘤免疫逃逸的机制之一。     

CD8+ Foxp3+ regulatory T cells mediate immunosuppression in prostate cancer.

PURPOSE: Although elevated proportions of CD4(+)CD25(+) regulatory T (Treg) cells have been shown in several types of cancers, very little is known about the existence and function of CD8(+) Treg cells in prostate cancer. In this study, we investigated prostate tumor-derived CD8(+) Treg cells and their function. EXPERIMENTAL DESIGN: Tumor-infiltrating lymphocytes (TIL) from fresh tumor specimens of patients with prostate cancer were generated and subjected to phenotypic and suppressive function analyses. In particular, we investigated the role and function CD8(+) Treg cells in prostate cancer. RESULTS: We show that high percentages of CD4(+)CD25(+) T cells are probably present in the majority (70%) of prostate TILs. Remarkably, both CD4(+) and CD8(+) T-cell subpopulations possessed potent suppressive activity. T-cell cloning and fluorescence-activated cell sorting analyses showed the presence of CD8(+)CD25(+) Treg cell clones that expressed FoxP3 and suppressed na?ve T-cell proliferation, in addition to the previously known CD4(+)CD25(+) Treg cells. These CD8(+) Treg cells suppressed na?ve T-cell proliferation mainly through a cell contact-dependent mechanism. Importantly, the suppressive function of CD8(+) Treg cells could be reversed by human Toll-like receptor 8 (TLR8) signaling. CONCLUSION: Our study shows that like CD4(+)CD25(+) Treg cells, CD8(+) Foxp3(+) Treg cells present in prostate tumor-derived TILs suppress immune responses and that their suppressive function can be regulated by TLR8 ligands, raising the possibility that the manipulation of Treg cell function by TLR8 ligands could improve the efficacy of immunotherapy for prostate cancer patients.     

Ex vivo expansion of CD8+CD56+ and CD8+CD56- natural killer T cells specific for MUC1 mucin

Prostate cancers express MUC1, but nearly all metastatic cells lack HLA class I molecules. Thus, a lymphocyte population that can sense its antigenic environment, while also able to react to stimuli of natural killer (NK) cells, may be a more versatile effector cell population for antitumor immune responses. Herein, we report that tumor-specific MUC1 peptide, interleukin 2, and interleukin 12 act synergistically to stimulate the ex vivo expansion of CD8(+)CD56(-) T cells and CD8(+)CD56(+) natural killer T (NKT) cells from the peripheral blood mononuclear cells of prostate cancer patients, as well as healthy male and female donors. Both the CD56(+) NKT cells and CD56(-) T cells lysed allogeneic mucin-bearing target cells, as well as NK target cells, but not lymphokine-activated killer target cells. However, the CD56(+) NKT cells displayed a 2-fold greater cytolytic activity than the CD56(-) T cells. The mucin-specific cytolytic activity and NK cytolytic activities for both lymphocyte populations were independent of HLA class I and CD1 molecules. The CD56(-) T cells up-regulated CD56 with continued antigenic stimulation in the presence of interleukin 12, suggesting that CD8(+)CD56(-) T cells are NKT cells. However, CD56(+) NKT cells expand poorly to continued stimulation. All mucin-stimulated NKT cells exhibited the activated/memory CD45RO phenotype. The NKT cell lines express the alpha/beta T-cell receptor (TCR). The TCR repertoire was limited and varied with cell line, but was not the V alpha 24V beta 11 TCR typically associated with NKT cells. Whereas CD161 is generally considered a marker of NKT cells, the mucin-stimulated NKT cells did not express this marker. Thus, we have described two phenotypically distinct NKT types that do not display a biased TCR repertoire, but do display specificity for a tumor-specific peptide antigen (CTL-like activity), as well as HLA class I-deficient target cells (NK-like activity).     

CD4+CD25+CCR6+调节性T细胞在小鼠乳腺癌模型中对CD8+T细胞的抑制作用

目的：观察CD4+CD25+CCR6+调节性T细胞（简称CCR6+Tregs）体内对CD8+T细胞功能的抑制作用,并探讨其与肿瘤免疫逃逸的关系。方法：建立4T1乳腺癌细胞荷瘤裸鼠模型,FACS分选CCR6+Tregs,检测其Foxp3的表达;FACS分选4T1特异性CD8+T细胞,CFSE标记后分别与CCR6+Tregs或CCR6Tregs共同过继转输入4T1荷瘤裸鼠体内,观察荷瘤裸鼠肿瘤生长情况和小鼠存活时间;FACS检测肿瘤组织中CD8+T细胞的增殖、细胞因子IFNγ的产生和颗粒酶B的表达情况。结果：CCR6+Tregs和CCR6Tregs均高表达Foxp3;CCR6+Tregs和CD8+T细胞共转输组4T1荷瘤裸鼠肿瘤的生长明显快于CCR6Tregs共转输组和CD8+T细胞单转输组,同时该组荷瘤裸鼠生存时间也明显缩短（P<0.05）;CCR6+Tregs和CD8+T细胞共转输组CD8+T细胞的增殖、IFNγ的产生和颗粒酶B的表达均明显低于CCR6Tregs共转输组和CD8+T细胞单转输组（P<0.05）。结论：CCR6+Tregs在体内可以有效抑制CD8+T细胞的功能,其在肿瘤免疫逃逸和肿瘤发生、发展中发挥重要作用。     

Role of IL-2, IL-4 and IL-6 in the growth and differentiation of tumor-specific CD4+ T helper and CD8+ T cytotoxic cells

We have earlier observed that 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU), a chemotherapeutic drug, cured 90-100% of mice bearing a syngeneic Ia- T-cell lymphoma (LSA) and furthermore, 100% of the BCNU-cured mice could reject homologous tumor rechallenge. In the present study, purified CD4+ and CD8+ T cells isolated from BCNU-cured mice were used to investigate the mechanism by which such T cells recognized and responded to the tumor-specific antigens. The responsiveness of CD4+ T cells to LSA was dependent on processing and presentation of tumor-specific antigens by syngenic Ia+ splenic antigen-presenting cells (APC). Such activated CD4+ T cells endogenously produced IL-2 but not IL-4 and only IL-2 acted as an autocrine growth factor inasmuch as anti-IL-2 receptor antibodies but not anti-IL-4 antibodies inhibited the CD4+ T cell proliferation. In contrast, the CD8+ T cells failed to produce endogenous growth factors when stimulated with LSA alone or with LSA plus APC, and therefore failed to proliferate. However, in the presence of exogenous recombinant IL-2 (rIL-2), CD8+ T cells could proliferate directly in response to LSA-stimulation, even in the absence of APC. Addition of exogenous rIL-4 alone to cultures induced CD4+ but not CD8+ T cells to proliferate. However, rIL-4 in the presence of rIL-2, could synergize and induce tumor-specific proliferation of CD8+ cells. These data suggested that for IL-4 to act as a T-cell growth factor, the presence of IL-2 was essential, either in the form of endogenously secreted IL-2 (CD4+ T cells) or exogenous IL-2 (for CD8+ T cells). In contrast to rIL-2 and rIL-4, rIL-6 failed to induce growth when used alone or in combination with rIL-2 or rIL-4. Furthermore, when tested individually, only rIL-2 but not rIL-4 or rIL-6 could support the cytotoxic differentiation of CD8+ T cells. The present study suggests that the early events in responsiveness to LSA tumor may involve activation of the IL-2-producing Th1 subpopulation of CD4+ helper cells which in turn activate IL-2 dependent CD8+ cytotoxic T cells. IL-4 if produced subsequently, may act synergistically with IL-2 to promote the growth of CD4+ and CD8+ T cells.     

CD8+ T cell-mediated control of distant tumours following local photodynamic therapy is independent of CD4+ T cells and dependent on natural killer cells

Cancer survival rates decrease in the presence of disseminated disease. However, there are few therapies that are effective at eliminating the primary tumour while providing control of distant stage disease. Photodynamic therapy (PDT) is an FDA-approved modality that rapidly eliminates local tumours, resulting in cure of early disease and palliation of advanced disease. Numerous pre-clinical studies have shown that local PDT treatment of tumours enhances anti-tumour immunity. We hypothesised that enhancement of a systemic anti-tumour immune response might control the growth of tumours present outside the treatment field. To test this hypothesis we delivered PDT to subcutaneous (s.c.) tumours of mice bearing both s.c. and lung tumours and monitored the growth of the untreated lung tumours. Our results demonstrate that PDT of murine tumours provided durable inhibition of the growth of untreated lung tumours. The inhibition of the growth of tumours outside the treatment field was tumour-specific and dependent on the presence of CD8(+) T cells. This inhibition was accompanied by an increase in splenic anti-tumour cytolytic activity and by an increase in CD8(+) T cell infiltration into untreated tumours. Local PDT treatment led to enhanced anti-tumour immune memory that was evident 40 days after tumour treatment and was independent of CD4(+) T cells. CD8(+) T cell control of the growth of lung tumours present outside the treatment field following PDT was dependent upon the presence of natural killer (NK) cells. These results suggest that local PDT treatment of tumours lead to induction of an anti-tumour immune response capable of controlling the growth of tumours outside the treatment field and indicate that this modality has potential in the treatment of distant stage disease.     

CD4+ and CD8+ T cells have opposing roles in breast cancer progression and outcome

The Cancer Immunoediting concept has provided critical insights suggesting dual functions of immune system during the cancer initiation and development. However, the dynamics and roles of CD4⁺ and CD8⁺ T cells in the pathogenesis of breast cancer remain unclear. Here we utilized two murine breast cancer models (4T1 and E0771) and demonstrated that both CD4⁺ and CD8⁺ T cells were increased and involved in immune responses, but with distinct dynamic trends in breast cancer development. In addition to cell number increases, CD4⁺ T cells changed their dominant subsets from Th1 in the early stages to Treg and Th17 cells in the late stages of the cancer progression. We also analyzed CD4⁺ and CD8⁺ T cell infiltration in primary breast cancer tissues from cancer patients. We observed that CD8⁺ T cells are the key effector cell population mediating effective anti-tumor immunity resulting in better clinical outcomes. In contrast, intra-tumoral CD4⁺ T cells have negative prognostic effects on breast cancer patient outcomes. These studies indicate that CD4⁺ and CD8⁺ T cells have opposing roles in breast cancer progression and outcomes, which provides new insights relevant for the development of effective cancer immunotherapeutic approaches.     

Immune activation status of CD8+ T cells infiltrating non-small cell lung cancer

In a variety of human cancers, the presence of tumor-infiltrating T lymphocytes (TILs) is associated with tumor regression and favorable prognosis. Local interferon (IFN)-gamma secretion from activated T cells is supposed to induce a specific immune response leading to tumor-specific cytotoxicity. Nonetheless, significance and properties of TILs still remains controversial in lung cancer patients. We determined CD8+ T cell counts in 31 patients with non-small cell lung cancer (NSCLC) by immunohistochemistry, and assessed T-cell immune activation status in a subset of patients by measuring IFN-gamma mRNA expression by quantitative PCR (TaqMan). Semi-quantitative immunohistochemical analysis revealed significantly higher CD8+ T cell counts within the tumor as when compared to the invasive margin. CD8+ T cells immune activation status, represented in the IFN-gamma/CD8 mRNA ratio, correlated with the median number of CD8+ T cells presented at the tumor-host interface. Neither tumor histology and grade, nor CD8+ T cell counts and IFN-gamma/CD8 ratio could demonstrate an influence on overall survival in these patients. Our results indicate that CD8+ T cells infiltrating the tumor cell nests may be inadequately activated and thus incapable of mounting an effective anti-tumor immune response.     

CD4+FoxP3+ regulatory T cells gradually accumulate in gliomas during tumor growth and efficiently suppress antiglioma immune responses in vivo

The suppressive activity of regulatory T cells (Treg) has been implicated as an important factor limiting immune mediated destruction of tumor cells. However, not much is known about the presence and function of Treg within tumors. Here we show in a syngeneic murine glioma model a time-dependent accumulation of CD4+FoxP3+ Treg in brain tumors. Further analysis revealed a time-dependent upregulation of CD25, CTLA-4, GITR and CXCR4 on intratumoral CD4+FoxP3+ Treg during tumor growth. Moreover, freshly isolated intratumoral Treg were highly suppressive when tested directly ex vivo. Treatment with anti-CD25 monoclonal antibodies (mAbs) significantly reduced the number of these highly suppressive CD4+FoxP3+ cells within the growing tumor and provoked a CD4 and CD8 T cell dependent destruction of the glioma cells. Combining Treg depletion with administration of blocking CTLA-4 mAbs further boosted glioma-specific CD4+ and CD8+ effector T cells as well as antiglioma IgG2a antibody titers resulting in complete tumor eradication without any signs of autoimmunity. These data illustrate that intratumoral accumulation and activation of CD4+FoxP3+ Treg act as a dominant immune escape mechanism for gliomas and underline the importance of controlling tumor-infiltrating Treg in glioma immunotherapy.     

Inhibition of melanoma growth after treatment with dendritic cells in a Tyr-SV40E murine model requires CD4+ T cells but not CD8+ T cells

Melanomas are promising targets for immunotherapy, as they express a number of tissue-specific antigens against which immune responses can be elicited. We have previously described transgenic mice in which malignant cutaneous melanomas are produced. The 1042 melanoma cell line, derived from a primary melanoma in one of these mice, was used here to generate tumours by subcutaneous inoculation in syngeneic animals. All mice injected with 1 x 10(6) cells of the 1042 cell line developed a tumour. CD4+ T cells, CD8+ T cells and macrophages infiltrated the tumours. Treatment with dendritic cells pulsed with peptides from melanogenic proteins slowed tumour growth and resulted in increased numbers of infiltrating lymphocytes and macrophages, expansion of CD4+ T cells specific for 1042 cell antigens, and increased levels of 1042-specific immunoglobulin G1 (IgG1) and IgM in serum. The frequency of cytotoxic T lymphocytes (CTLs) specific for the MART-1 melanocytic antigen did not increase after dendritic cell treatment. Indeed, the presence of CD8+ T cells was apparently not required for the anti-tumour effects: slowing of tumour growth was not abrogated in animals depleted of CD8+ T cells using antibodies, or in syngeneic CD8-/- animals. In contrast, treatment with dendritic cells + peptides was ineffective after depletion of CD4+ T cells and in syngeneic CD4-/- mice. This experimental system therefore provides an opportunity to investigate CD4-dependent anti-tumour effector mechanisms, and for studies designed to activate the quiescent CTLs which infiltrate melanomas.     

Concurrent infiltration by CD8+ T cells and CD4+ T cells is a favourable prognostic factor in non-small-cell lung carcinoma

The purpose of this study was to clarify the relationship between the number of tumour-infiltrating T lymphocytes and the clinicopathological features and clinical outcome in patients with non-small-cell lung cancer (NSCLC). Tissue specimens from 109 patients who underwent surgical resection for NSCLC were immunohistochemically analysed for CD4 and CD8 expression. Patients were classified into two groups according to whether their tumours exhibited a 'high' or 'low' level of CD8(+) or CD4(+) lymphocyte infiltration. Although the level of infiltration by CD8(+) T cells alone had no prognostic significance, the survival rate for patients with both 'high' CD8(+) and 'high' CD4(+) T-cell infiltration was significantly higher than that for the other groups (log-rank test, P=0.006). Multivariate analysis indicated that concomitant high CD8(+) and high CD4(+) T-cell infiltration was an independent favourable prognostic factor (P=0.0092). In conclusion, the presence of high levels of both CD8(+) T cells and CD4(+) T cells is a significant indicator of a better prognosis for patients with NSCLC, and cooperation between these cell populations may allow a significantly more potent antitumour response than either population alone.     

Detection of clonal Epstein-Barr virus in malignant proliferation of peripheral blood CD3+ CD8+ T cells.

Epstein Barr virus (EBV) DNA was detected in a monoclonal proliferation of T cells in a three-year-old girl who presented with a history of fever, hepatosplenomegaly, and generalised lymphadenopathy. The disease ran a rapid, fulminant course and the patient died 11 days after presentation. Examination of the blood showed a lymphocytosis of 50 x 10(9)/l with all the cells showing the morphology of large granular lymphocytes. These cells were CD2+3+8+25+. Cytogenetic studies showed the presence of a 6q- clone. Southern blotting and hybridisation with a constant region probe for the T-cell receptor (TCR) beta chain gene showed clonal rearrangement of the TCR beta gene. Hybridisation of the Southern blot to the EBV XhoI probe revealed a clonal pattern of episomal EBV DNA. Our results establish the association between clonal EBV infection to a malignant proliferation of peripheral blood CD8+ T cells.     

CD4+ T cells are able to promote tumor growth through inhibition of tumor-specific CD8+ T-cell responses in tumor-bearing hosts

Modulation of the immune response by established tumors may contribute to the limited success of therapeutic vaccination for the treatment of cancer compared with vaccination in a preventive setting. We analyzed the contribution of the CD4+ T-cell population to the induction or suppression of tumor-specific CD8+ T cells in a tumor model in which eradication of tumors crucially depends on CD8+ T cell-mediated immunity. Vaccine-mediated induction of protective antitumor immunity in the preventive setting (i.e., before tumor challenge) was CD4+ T cell dependent because depletion of this T-cell subset prevented CD8+ T-cell induction. In contrast, depletion of CD4+ cells in mice bearing established E1A+ tumors empowered the mice to raise strong CD8+ T-cell immunity capable of tumor eradication without the need for tumor-specific vaccination. Spontaneous eradication of tumors, which had initially grown out, was similarly observed in MHC class II-deficient mice, supporting the notion that the tumor-bearing mice harbor a class II MHC-restricted CD4+ T-cell subset capable of suppressing a tumor-specific CD8+ T-cell immune response. The deleterious effects of the presence of CD4+ T cells in tumor-bearing hosts could be overcome by CD40-triggering or injection of CpG. Together these results show that CD4+ T cells with a suppressive activity are rapidly induced following tumor development and that their suppressive effect can be overcome by agents that activate professional antigen-presenting cells. These observations are important for the development of immune interventions aiming at treatment of cancer.     

Sustained antigen-specific antitumor recall response mediated by gene-modified CD4+ T helper-1 and CD8+ T cells

Given that specific subsets of T helper 1 (Th1) and T helper 2 (Th2) CD4(+) T cells have been shown to play key roles in tumor rejection models, we wanted to assess the contribution of either Th1 or Th2 CD4(+) cell subtypes for redirected T-cell immunotherapy. In this study, we have developed a novel method involving retroviral transduction and in vitro T-cell polarization to generate gene-engineered mouse CD4(+) Th1 and Th2 cells or T helper intermediate (Thi) cells expressing an anti-erbB2-CD28-zeta chimeric receptor. Gene-modified Th1 and Th2 polarized CD4(+) cells were characterized by the preferential secretion of IFN-gamma and interleukin-4, respectively, whereas Thi cells secreted both cytokines following receptor ligation. In adoptive transfer studies using an erbB2(+) lung metastasis model, complete survival of mice was observed when transduced Th1, Th2, or Thi CD4(+) cells were transferred in combination with an equivalent number of transduced CD8(+) T cells. Tumor rejection was consistently associated with transduced T cells at the tumor site and interleukin-2 secretion. However, the surviving mice treated with gene-modified Th1 CD4(+) cells were significantly more resistant to a subsequent challenge with a different erbB2(+) tumor (4T1.2) implanted s.c. This result correlated with both increased expansion of Th1 CD4(+) and CD8(+) T cells in the blood and a greater number of these cells localizing to the tumor site following rechallenge. These data support the use of gene-modified CD4(+) Th1 and CD8(+) T cells for mediating a sustained antitumor response.     

Helper function of memory CD8+ T cells: heterologous CD8+ T cells support the induction of therapeutic cancer immunity

In contrast to the well-established efficacy of preventive vaccines, the effectiveness of therapeutic vaccines remains limited. To develop effective vaccination regimens against cancer, we have analyzed the effect of effector and memory CD8+ T cells on the ability of dendritic cells to mediate the immunologic and antitumor effects of vaccination. We show that in contrast to effector CD8+ T cells that kill antigen-carrying dendritic cells, IFNgamma-producing memory CD8+ T cells act as "helper" cells, supporting the ability of dendritic cells to produce interleukin-12 (IL-12) p70. Promoting the interaction of tumor antigen-carrying dendritic cells with memory-type "heterologous" (tumor-irrelevant) CD8+ T cells strongly enhances the IL-12p70-dependent immunogenic and therapeutic effects of vaccination in the animals bearing established tumors. Our data show that the suppressive and helper functions of CD8+ T cells are differentially expressed at different phases of CD8+ T-cell responses. Selective performance of helper functions by memory (in contrast to effector) CD8+ T cells helps to explain the phenomenon of immune memory and facilitates the design of effective therapeutic vaccines against cancer and chronic infections.     

Maximal T cell-mediated antitumor responses rely upon CCR5 expression in both CD4(+) and CD8(+) T cells

Immune responses against cancer rely upon leukocyte trafficking patterns that are coordinated by chemokines. CCR5, the receptor for chemotactic chemokines MIP1alpha, MIP1beta, and RANTES (CCL3, CCL4, CCL5), exerts major regulatory effects on CD4(+)- and CD8(+) T cell-mediated immunity. Although CCR5 and its ligands participate in the response to various pathogens, its relevance to tumoral immune control has been debated. Here, we report that CCR5 has a specific, ligand-dependent role in optimizing antitumor responses. In adoptive transfer studies, efficient tumor rejection required CCR5 expression by both CD4(+) and CD8(+) T cells. CCR5 activation in CD4(+) cells resulted in CD40L upregulation, leading to full maturation of antigen-presenting cells and enhanced CD8(+) T-cell crosspriming and tumor infiltration. CCR5 reduced chemical-induced fibrosarcoma incidence and growth, but did not affect the onset or progression of spontaneous breast cancers in tolerogenic Tg(MMTV-neu) mice. However, CCR5 was required for TLR9-mediated reactivation of antineu responses in these mice. Our results indicate that CCR5 boosts T-cell responses to tumors by modulating helper-dependent CD8(+) T-cell activation.