ABSTRACT
DC are unique antigen presenting cells, and their ability to induce proliferation of T cells in a mixed leukocyte reaction (MLR) assay is commonly used for the evaluation of their function. To determine the mechanisms involved in DC-induced T cell activation in a primary MLR assay, a variety of different agents were examined in this study that interfere with DNA synthesis, membrane organization, protein synthesis, and maturation induced by bacterial products. While only live DC were able to induce T cell proliferation in the MLR assay, irradiation of DC did not influence their stimulatory capacity. Fixation of DC membrane with paraformaldehyde resulted in a loss of DC capacity to induce T cell proliferation demonstrating that physical organization of the plasma membranes plays an important role in the induction of T cell activation. In addition, the pretreatment of DC with cycloheximide revealed that protein synthesis was not critical for the ability of DC to activate T cells. Finally, Staphylococcus aureus-mediated activation of DC significantly increased T cell proliferation and this effect was not dependent on IL-12 production of DC since DC generated from IL-12 knockout mice were not different from wild type DC. In summary, these data suggest that DC membrane structures are responsible for the antigen presentation and co-stimulation and play a key role in T cell recognition and activation by DC.
Subject(s)
Dendritic Cells/immunology , Lymphocyte Activation/immunology , T-Lymphocytes/immunology , Animals , Cell Survival/immunology , Cell Survival/radiation effects , Cycloheximide/pharmacology , Dendritic Cells/drug effects , Dendritic Cells/microbiology , Dendritic Cells/radiation effects , Fixatives/pharmacology , Formaldehyde/pharmacology , Interleukin-12/deficiency , Interleukin-12/genetics , Interleukin-12/physiology , Lymphocyte Activation/radiation effects , Lymphocyte Culture Test, Mixed/methods , Male , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Knockout , Polymers/pharmacology , Protein Synthesis Inhibitors/pharmacology , Staphylococcus aureus/immunology , T-Lymphocytes/radiation effectsABSTRACT
We have shown that prostate cancer (PCa) causes apoptosis of dendritic cells (DC), which might block the development of specific antitumor immune responses. Analysis of murine prostatic carcinoma tissues revealed the significant decrease in intratumoral DC number during tumor progression. We demonstrated that the cytokine-mediated increase in DC survival was accompanied by an elevated expression of the anti-apoptotic protein Bcl-xL. Next, we evaluated the resistance to tumor-induced apoptosis and the antitumor efficiency of genetically engineered DC overexpressing Bcl-xL. DC were transduced with an adenoviral vector encoding the murine Bcl-xL gene and injected intratumorally. Data analysis revealed that treatment of PCa-bearing mice with Bcl-xL-transduced DC resulted in significant inhibition of tumor growth compared with the administration of nontransduced DC. Thus, our data suggest that the protection of DC from PCa-induced apoptosis might significantly increase the efficacy of DC-based therapies in cancer even in the absence of available tumor-specific Ags.
