Blockade of CCR7 leads to decreased dendritic cell migration to draining lymph nodes and promotes graft survival in low-risk corneal transplantation.

The chemokine receptor CCR7 is essential for migration of mature dendritic cells (DCs) to the regional lymph nodes, and it has been shown that blocking of CCR7 improves graft survival after high-risk corneal transplantation in vascularized recipient corneas. However, it is so far unknown whether blocking of CCR7 reduces migration of DCs from the avascular cornea to the draining lymph nodes and whether this leads to improved graft survival also in the low-risk setting of corneal transplantation, which accounts for the majority of perforating transplantations performed. Therefore, in this study, pellets containing Freund's adjuvant and bovine serum albumin (BSA) conjugated to Alexa488 fluorescent dye were implanted into the corneal stroma of BALB/c mice to analyze antigen uptake by corneal DCs and their migration to the regional lymph nodes. After pellet implantation, mice were either treated by local administration of a CCR7 blocking fusion protein that consisted of CCL19 fused to the Fc part of human IgG1 or a control-IgG. In vivo fluorescence microscopy showed uptake of Alexa488-conjugated BSA by corneal DCs within 8 h. Furthermore, analysis of single cell suspensions of draining lymph nodes prepared after 48 h revealed that 2.1 ± 0.3% of CD11c(+) cells were also Alexa488(+). Importantly, DC migration was significantly reduced after topical administration of CCL19-IgG (1.2 ± 0.2%; p < 0.05). To test the effect of CCR7 blockade on graft rejection after allogeneic low-risk keratoplasty, corneal transplantations were performed using C57BL/6-mice as donors and BALB/c-mice as recipients. Treatment mice received two intraperitoneal loading doses of CCL19-IgG prior to transplantation, followed by local treatment with CCL19-IgG containing eye drops for the first two weeks after transplantation. Control mice received same amounts of control-IgG. Kaplan-Meier survival analysis showed that in the CCL19-IgG treated group, 76% of the grafts survived through the end of the 8 week observation period, whereas 38% of the grafts survived in the control group (p < 0.05). Taken together, our study shows that blockade of CCR7 reduces the migration of mature corneal DCs to the draining lymph nodes and leads to improved graft survival in low-risk corneal transplantation.

A new method to monitor antigen-specific CD8+ T cells, avoiding additional target cells and the restriction to human leukocyte antigen haplotype.

Therapeutic vaccination of cancer patients with dendritic cells aims at inducing a strong tumor-specific T-cell response. Testing new target antigens for their immunogenicity is crucial to evaluate their suitability for this approach. Here we demonstrate a comfortable and reliable method to detect antigen-specific CD8(+) T-cell responses without the knowledge of the precise T-cell epitope and without the usage of additional target cells. We used the CD8(+) T cells themselves and electroporated them with RNA encoding the respective tumor antigen. The cells expressed, processed and presented the antigen and were capable of stimulating each other in functional readouts. For the model antigen MelanA, the number of interferon-γ-secreting cells obtained with this method highly correlated with the numbers obtained by exogenous peptide loading (R(2)=0.8). The method was also applicable for the tumor-associated antigen Wilms' tumor protein 1. This system is quick and easy to perform, independent of the donors human leukocyte antigen type and circumvents the need for additional cells as targets. It can be used in preclinical research to test new antigens for their immunogenic potential and for immunomonitoring in cancer patients.

Transfer of mRNA encoding recombinant immunoreceptors reprograms CD4+ and CD8+ T cells for use in the adoptive immunotherapy of cancer.

Human T lymphocytes can be redirected with a new defined specificity by expression of a chimeric T-cell receptor (immunoreceptor) for the use in adoptive immunotherapy of cancer. Whereas standard procedures use retroviral gene transduction to constitutively express immunoreceptors in T cells, we here explored for the first time mRNA electroporation to achieve transient immunoreceptor expression, and thereby minimizing the risk of persistence of potential autoaggression. CD4(+) and CD8(+) T cells were efficiently transfected with immunoreceptors specific for ErbB2 and CEA. The immunoreceptor expression was transient with half-maximal expression at day 2 and no detectable immunoreceptor expression at day 9 after electroporation. Immunoreceptor-transfected T cells were specifically activated upon coincubation with ErbB2(+) and CEA(+) tumor cells, respectively, resulting in secretion of interferon-gamma (IFNgamma), interleukin-2 (IL-2), and tumor necrosis factor-alpha (TNFalpha). Furthermore, immunoreceptor-transfected CD8(+) T cells specifically lysed ErbB2(+) and CEA(+) tumor cells, respectively. The RNA-transfected T cells retained their cytotoxic function after 2 days of activation and exhibited cytolytic activities like retrovirally transduced T cells. RNA electroporation of T cells thereby provides a versatile tool for transient immunoreceptor expression, which may be of advantage in avoiding the persistence of unintended autoaggression.

Resveratrol induces extensive apoptosis by depolarizing mitochondrial membranes and activating caspase-9 in acute lymphoblastic leukemia cells.

Resveratrol, a plant antibiotic, has been found to have anticancer activity and was recently reported to induce apoptosis in the myeloid leukemia line HL60 by the CD95-CD95 ligand pathway. However, many acute lymphoblastic leukemias (ALLs), particularly of B-lineage, are resistant to CD95-mediated apoptosis. Using leukemia lines derived from patients with pro-B t(4;11), pre-B, and T-cell ALL, we show in this report that resveratrol induces extensive apoptotic cell death not only in CD95-sensitive leukemia lines, but also in B-lineage leukemic cells that are resistant to CD95-signaling. Multiple dose treatments of the leukemic cells with 50 microM resveratrol resulted in >/=80% cell death with no statistically significant cytotoxicity against normal peripheral blood mononuclear cells under identical conditions. Resveratrol treatment did not increase CD95 expression or trigger sensitivity to CD95-mediated apoptosis in the ALL lines. Inhibition of CD95-signaling with a CD95-specific antagonistic antibody indicated that CD95-CD95 ligand interactions were not involved in initiating resveratrol-induced apoptosis. However, in each ALL line, resveratrol induced progressive loss of mitochondrial membrane potential as measured by the dual emission pattern of the mitochondria-selective dye JC-1. The broad spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone failed to block the depolarization of mitochondrial membranes induced by resveratrol, further indicating that resveratrol action was independent of upstream caspase-8 activation via receptor ligation. However, increases in caspase-9 activity ranged from 4- to 9-fold in the eight cell lines after treatment with resveratrol. Taken together, these results point to a general mechanism of apoptosis induction by resveratrol in ALL cells that involves a mitochondria/caspase-9-specific pathway for the activation of the caspase cascade and is independent of CD95-signaling.

Regulation of CD95 expression and CD95-mediated cell death by interferon-gamma in acute lymphoblastic leukemia with chromosomal translocation t(4;11).

The regulatory effects of IFNgamma on CD95 expression and CD95-mediated cell death were investigated in three high-risk pro-B acute lymphoblastic leukemia (ALL) lines that carry the chromosomal translocation t(4;11)(q21;q23). These leukemias are characteristically refractory to conventional chemotherapeutic treatments operating through the induction of apoptosis. However, the mechanisms leading to increased cell survival and resistance to cell death in these leukemias are largely unknown. Interferon-gamma (IFNgamma), a potent inhibitor of hematopoiesis, acts in part by upregulating CD95 and sensitizing cells to CD95-induced apoptosis. The t(4;11) lines SEM, RS4;11, and MV4;11 expressed low levels of CD95, but were completely resistant to CD95-mediated death. Addition of IFNgamma markedly upregulated CD95 expression in SEM (8-9-fold), RS4;11 (2-3-fold), and MV4;11 (2-3-fold) lines. However, after treatment with IFNgamma, only an 11% increase in sensitivity to CD95-mediated cell death was observed in SEM cells, whereas RS4;11 and MV4;11 cells remained resistant. Cycloheximide, but not actinomycin D or brefeldin A, increased CD95-specific cell death only in IFNgamma-treated RS4;11 cells by approximately 12%. Abundant levels of Bcl-2 and Bcl-XL, known to inhibit CD95-signaling in some cells, were present suggesting a possible role for both molecules in the resistance to CD95-mediated cell death. Resistance of the leukemic blasts to CD95-mediated cell death and the failure of IFNgamma to substantially sensitize the CD95-signaling pathway may contribute to the highly malignant phenotype of pro-B ALL with translocation t(4;11).

Carnosol-induced apoptosis and downregulation of Bcl-2 in B-lineage leukemia cells.

Carnosol, a phenolic compound extracted from the herb rosemary has been reported to have anti-cancer activity. We investigated whether carnosol was cytotoxic against several pro-B and pre-B acute lymphoblastic leukemia (ALL) lines. In all ALL lines tested, carnosol induced apoptotic cell death distinguished by loss of nuclear DNA, externalization of cell membrane phosphatidylserine, and depolarization of mitochondrial membranes. Flow cytometric measurement of Bcl-2 protein levels revealed that carnosol induced a 34-53% decrease in Bcl-2 in the cell population exhibiting a viable phenotype prior to detectable apoptotic changes in morphology. These results suggest that carnosol may be useful as a novel chemotherapeutic agent against B-lineage leukemias, and possibly other types of cancers that express high levels of the protective protein, Bcl-2.