The antitumor effect of IFN-α is mediated by the activation of CTLs, NK cells, and the generation of highly potent Ag-presenting dendritic cells (IFN-DCs). In this study, we show that IFN-DCs generated in vitro from monocytes express CD56 on their surface, a marker which has been thought to be specific for NK cells. FACS analyses of CD56+ and CD56− IFN-DCs showed a nearly identical pattern for most of the classical DC markers. Importantly, however, only CD56+ IFN-DCs exhibited cytolytic activity up to 24% that could almost completely be blocked (−81%) after coincubation with anti-TRAIL. Intracytoplasmatic cytokine staining revealed that the majority of IFN-DCs independently of their CD56 expression were IFN-γ positive as well. In contrast, CD56+ IFN-DCs showed stronger capacity in stimulating allogenic T cells compared with CD56− IFN-DC. Based on these results, five patients with metastasized medullary thyroid carcinoma were treated for the first time with monocyte-derived tumor Ag-pulsed IFN-DCs. After a long term follow-up (in mean 37 mo) all patients are alive. Immunohistochemical analyses of delayed-type hypersensitivity skin reaction showed a strong infiltration with CD8+ cells. In two patients no substantial change in tumor morphology was detected. Importantly, by analyzing PBMCs, these patients also showed an increase of Ag-specific IFN-γ-secreting T cells. In summary, we here describe for the first time that cytotoxic activity of IFN-DCs is mainly mediated by an IFN-DC subset showing partial phenotypic and functional characteristics of NK cells. These cells represent another mechanism of the antitumor effect induced by IFN-α.

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Background: Long-menu questions (LMQs) are viewed as an alternative method for answering open-ended questions (OEQs) in computerized assessment. So far this question type and its influence on examination scores have not been studied sufficiently. However, the increasing use of computerized assessments will also lead to an increasing use of this question type.

The existence of inherited aggressive forms of medullary thyroid carcinoma (MTC) and their resistance to classical therapies make it a prime candidate for adoptive immunotherapy. Highly potent antigen-presenting cells, namely dendritic cells (DCs), may serve as an interesting tool for anticancer vaccination. Here we report on the IN VITRO findings of a vaccination trial in five MTC patients, who were treated with a new DC generation protocol consisting of granulocyte-macrophage colony-stimulating factor and interferon-alpha (IFN-DCs). These cells were pulsed with tumor-specific calcitonin and administered twice. In two patients who responded to therapy we found a large increase (in mean 2.9+/-1.9%) of antigen-specific IFN-gamma-secreting CD4+ cells as well as an increase of granzyme B positive CD8+ cells (mean 2.2+/-0.2%) in the peripheral blood. In parallel, a decrease of CD4+/CD25+/FoxP3+ regulatory T cells was seen. Importantly, IN VITRO stimulation of PBMC with 10 different 15mer calcitonin peptides resulted in the identification of two HLA class II epitope regions within the central part of full-length calcitonin. These data were in accordance with the results drawn from the computer-based algorithm epitope prediction software SYFPEITHI. Measurement of different pro- and anti-angiogenic factors did not allow for a distinct outcome of prediction of the treated patients. In summary, we have demonstrated that immunization with IFN-DCs leads to a tumor epitope-specific immune response in MTC patients and may, therefore, represent a promising tool for future vaccination trials.