IntroductionThe primary objective of cancer immunotherapy is to promote tumor elimination through the activation of innate and adaptive immune responses. Successful immunotherapy relies on vaccination strategies endowed with the dual capability of inducing tumor-specific lymphocytes while overcoming the mechanisms of immune tolerance. CD4 ϩ CD25 ϩ FoxP3 ϩ regulatory T lymphocytes (Tregs) critically contribute to the occurrence and persistence of tumor-induced tolerance. 1 An increase in the frequency of these immunosuppressive cells in cancer patients has been widely reported. Treg expansion observed during tumor progression may result from the proliferation of naturally occurring Tregs (nTregs) or from the conversion of CD4 ϩ CD25 Ϫ FoxP3 Ϫ T cells into CD4 ϩ CD25 ϩ FoxP3 ϩ Tregs (iTregs). 2,3 Tregs dampen immune responses by suppressing the function of the effectors CD4 ϩ , CD8 ϩ , and natural killer (NK) cells [4][5][6][7] and by inhibiting dendritic cell activation. [8][9][10] Because Tregs are one of the main barriers for the eradication of tumors by immune cells, their therapeutic depletion or their functional inactivation using drugs or antibodies improves responses to cancer immunotherapy, such as dendritic cell-based vaccines. [11][12][13][14][15][16] However, the selective elimination or inactivation of Tregs constitutes a major challenge because these cells share the same surface markers as activated conventional, nonsuppressive T cells. Indeed, antibody-based approaches indistinguishably target both Tregs and activated effector T lymphocytes. Likewise, chemotherapeutic agents such as cyclophosphamide, which are used to eliminate Tregs, do not target these cells selectively.Several reports have indicated that the adoptive transfer of allogeneic T cells may increase the efficacy of tumor immunotherapy by providing adjuvant/"danger" signals to the host immune cells. 17,18 A method has been optimized allowing for the efficient generation in vitro of a large number of allogeneic CD3/CD28 cross-linked T helper-1 (Th-1) memory T cells. 19 Adoptive transfer of these Th-1 lymphocytes stimulates anticancer immunity and significantly improves the survival of mice lethally injected with BCL1 leukemia cells. 19,20 This effect partly stems from cytokine production by activated T lymphocytes, which foster the establishment of protective type-1 immune responses. 18 However, the effects of type I cytokines, including interferon-␥ (IFN-␥), on Tregs have been discrepant in previous studies. As an essential effector cytokine for cell-mediated immunity, exogenous or autocrine IFN-␥ has been reported to negatively regulate Treg generation. 21,22 Other studies have found that IFN-␥ enhances activation-induced cell death and that it thereby may regulate the expansion and persistence of effector T cells by promoting apoptosis. 23,24 In the present study, we report that effector-memory CD4 ϩ Th-1 (emTh-1) cells are capable not only of fostering the establishment of type-1 immune responses, but also of critically impairing t...

No abstract

We have previously reported on the anti-tumoral potential of a chaperone-rich cell lysate (CRCL) vaccine. Immunization with CRCL generated from tumors elicits specific T and NK cell-dependent immune responses leading to protective immunity in numerous mouse tumor models. CRCL provides both a source of tumor antigens and danger signals leading to dendritic cell activation. In humans, tumor-derived CRCL induces dendritic cell activation and CRCL-loaded dendritic cells promote the generation of cytotoxic T lymphocytes in vitro. The current study was designed to identify the signaling events and modifications triggered by CRCL in antigen presenting cells. Our results indicate that tumor-derived CRCL not only promotes the activation of dendritic cells, but also significantly fosters the function of macrophages that thus appear as major targets of this vaccine. Activation of both cell types is associated with the induction of the MAP kinase pathway, the phosphorylation of STAT1, STAT5 and AKT and with transcription factor NF-κB activation in vitro and in vivo. These results thus provide important insights into the mechanisms by which CRCL-based vaccines exert their adjuvant effects on antigen presenting cells.

Interleukin-33 (IL33) is a member of the IL-1 cytokine family. IL33 polymorphisms are strongly associated with asthma susceptibility and IL33 deletion attenuates asthma in mice. However, the use of mouse models to elucidate the role of IL-33 in asthma is hampered by notably different tissue-specific patterns of IL33 expression in humans and mice. To bypass this limitation, we generated mice carrying a 157 kB human BAC transgene (TG) that includes IL33 and its flanking sequences on chromosome 9. This TG contains protective alleles for a number of asthma-associated polymorphisms. Five founders with 1, 2, or 6 BAC copies were obtained. All were healthy, fertile, and transmitted the transgene at the expected Mendelian ratio. To compare expression of transgenic human (h) and endogenous mouse (m)IL33, mice were challenged intranasally with Alternaria, which induces rapid release of mIL-33 in the lungs. Bronchoalveolar lavage fluid analysis showed that hIL-33 was also induced by Alternaria. Analysis of lung RNA by real-time PCR showed that Alternaria-induced hIL33 transcription was TG copy number-dependent and comparable with that of mIL33. IL33 is known to be expressed by human but not mouse endothelial cells. Indeed, we found high levels of hIL33 RNA in endothelial cell-enriched mouse CD31+ lung cells while mIL33 was barely detectable. These results suggest that tissue-specific hIL33 expression is controlled by cis-acting element(s) within the IL33 locus. More generally, our BAC TG appears to include all cis-regulatory elements necessary for faithful tissue-specific and copy number-dependent regulation of hIL33 expression, suggesting our mice are an ideal tool to study IL33 and its role in asthma.