Generation of antigen-specific cytotoxic T lymphocytes using a leukemic plasmacytoid dendritic cell line as antigen presenting cells.

Establishment of a leukemia plasmacytoid dendritic cell line (PMDC05) and intra-lineage transformation from pDCs to mDCs in PMDC05 has been reported. In this paper, we show the applicability of PMDC05 for cellular immunotherapy. By stimulation with LPS, PMDC05 showed enhancement in expression of antigen presentation-associated surface molecules and production of cytokines (IL-12p70 and TNF-α). The antigen presenting ability was markedly increased in PMDC05 stimulated with LPS. By co-culturing of CD8(+) T cells with LPS-stimulated and WT1/CMVpp65 peptide-pulsed PMDC05, WT1/CMVpp65 tetramer(+) cytotoxic T lymphocytes were efficiently generated. These findings reveal the applicability of PMDC05 in cellular immunotherapy for tumor and severe viral infections.

WT1 peptide vaccination in a CML patient: induction of effective cytotoxic T lymphocytes and significance of peptide administration interval.

Although antigen-specific immune responses including cytotoxic T cells (CTLs) against antigen peptide could be enhanced after tumor antigen peptide vaccinations, the immune responses do not necessarily result in a decrease or eradication of tumor cells in the vaccination trials. We focused on whether antigen-specific CTLs could be damaged by the repeated stimulation of antigenic peptide and whether regulatory T (Treg) cells would be increased by the administration of WT1 peptide. We administered WT1 peptide 22 times over 18 months in a CML patient who was being treated with imatinib. Although WT1 peptide administration every 2 weeks did not show any beneficial effects on the minimal residual disease (copies of bcr-abl transcripts), the transcripts remarkably decreased to the level of major molecular response after changing the administration interval of WT1 peptide from 2 to 4 weeks. An ex vivo study demonstrated that re-stimulation with WT1 peptide made WT1-specific T cells less reactive to WT1 tetramers and the impaired reactivity of CTLs lasted at least for 1 week. In addition, the cytotoxicity of the T cells was hampered by re-stimulation. Treg cells increased up to more than fivefold at the end of the WT1 administration period. The present findings suggested that the administration of the peptide every 4 weeks is superior to every 2 weeks. In addition, the findings that Treg cells increased gradually in accordance with the duration of WT1 peptide administration revealed the significance of manipulating Treg cells for establishing an efficient tumor antigen peptide vaccination.

Transformation of dendritic cells from plasmacytoid to myeloid in a leukemic plasmacytoid dendritic cell line (PMDC05).

We investigated the transformation from pDCs to mDCs in a pDC line (PMDC05) which was established from a patient with pDC leukemia in our laboratory. PMDC05 cells were separated into two fractions according to the expression of BDCA1 and CD123. BDCA1(-)CD123(+) cells were found to be pDC-like cells by their morphology, surface phenotypes, mRNA expression and the function. In addition, BDCA1(-)CD123(+) cells were demonstrated to have a proliferating capacity and revealed the ability to transform to BDCA1(+)CD123(-) cells which showed mDC-like properties. Our data demonstrated the possibility of transformation from pDCs to mDCs in human DC lineage.

A leukemic plasmacytoid dendritic cell line, PMDC05, with the ability to secrete IFN-alpha by stimulation via Toll-like receptors and present antigens to naïve T cells.

We established a plasmacytoid dendritic cell (pDC) line (PMDC05) from leukemia cells of pDC leukemia. PMDC05 cells were positive for CD4, CD56, CD33, HLA-DR, CD123 (IL-3Ralpha) and CD86 in the absence of lineage markers. mRNA of TLR1, TLR2, TLR4, TLR7 and TLR9 was clearly expressed and among these TLRs, TLR7 was prominent. Production of IFN-alpha and IL-12 in PMDC05 was enhanced by the stimulation with CpG-A and LPS, respectively. PMDC05 possessed a considerable antigen presenting ability, which was enhanced by culturing with IL3, influenza virus or LPS. PMDC05 could be a useful tool for investigating the pathophysiology of pDCL.

Induction of antigen-specific cytotoxic T lymphocytes by using monocyte-derived DCs transfected with in vitro-transcribed WT1 or SART1 mRNA.

To evaluate the usefulness of monocyte-derived dendritic cells transfected with tumor antigen mRNA for dendritic cell-based antitumor immunotherapy, we attempted to generate antigen-specific cytotoxic T cells by priming lymphocytes with monocyte-derived dendritic cells transfected with in vitro-transcribed tumor antigen mRNA. Mature monocyte-derived dendritic cells were generated from microbeads-separated CD14(+) cells by culturing with GM-CSF/IL-4 for 7 days and with TNF-alpha, IL-1alpha, IL-6, and PGE(2) for the last one day. Monocyte-derived dendritic cells, lymphocytes, and target cells, which were positive for HLA-A24, were used in the present study. Although lymphocytes prestimulated with untransfected monocyte-derived dendritic cells did not possess the cytotoxic ability against the target cells in a (51)Cr-release cytotoxicity assay, lymphocytes primed with tumor antigen RNA-transfected monocyte-derived dendritic cells were cytotoxic against the tumor antigen-expressing cells but not against the target cells without the expression of the antigen. The cytotoxic ability of the lymphocytes was blocked by the addition of antibodies against MHC class I but not by antibodies against MHC class II. These findings revealed that monocyte-derived dendritic cells transfected with WT1 or SART1 mRNA are able to induce tumor antigen-specific cytotoxic T cells and applicable for antitumor dendritic cell-based cellular immunotherapy.