A leukemic plasmacytoid dendritic cell line (PMDC05) as potent antigen presenting cells for anti-tumor cellular immunothrerapy (95.8)

Abstract

Abstract We established a leukemic plasmacytoid dendritic cell (pDC) line (PMDC05) with potent antigen presenting capacity from leukemia cells of a patient with pDC acute leukemia. PMDC05 was positive for CD4, CD56, CD33, HLA-DR, CD123 (IL-3Rα) and CD86 in the absence of lineage markers. mRNA of TLR1, TLR2, TLR4, TLR7 and TLR9 were clearly expressed and among these TLRs, TLR7 was prominent. By culturing PMDC05 with IL-3, CpG-B or LPS, the expression of CD1a, CD80, CD83, CD86 or HLA-DR was remarkably enhanced. Production of IFN-α and IL-12p70 was enhanced by the stimulation with CpG-A and LPS, respectively. PMDC05, which was stimulated with 0.1 μg/mL LPS and loaded with 10 μg/mL WT1 peptides (HLA-A*2402-restricted, modified-type 9-mer peptide; CYTWNQMNL) for 24 hours, was irradiated (60 Gy) and co-cultured with allogeneic CD8+ T cells purified from PB-MNCs of HLA-A*2402+ healthy donor (PMDC05:CD8+ Tcells = 1:10). Induction of WT1-specific CTLs was evaluated by flow cytometry analysis using HLA-A*2402 WT1 tetramer every week. Although Daudi pulsed with WT1 peptides could not induce WT1 tetramer+CD8+ T cells during the co-culture up to 7 weeks, PMDC05 began to induce WT1 tetramer+CD8+ T cells at week 4 and the percentage of WT1 tetramer+ T cells in CD8+ T cells rose to more than 75% at week 7. These data suggested that PMDC05 could be efficiently used for generating CTLs specific for antigens of tumors and could be applicable for cellular immunotherapy for tumors.