Various 'dendritic cell antigens' are already expressed on uncultured blasts in acute myeloid leukemia and myelodysplastic syndromes.

AIM AND METHODS: Leukemia-derived dendritic cells (DC(leu)) potentially present the whole leukemic antigen repertoire. We studied antigen-expression profiles of blasts/dendritic cells (DCs) generated from 137 acute myeloid leukemia (AML)/49 myelodysplastic syndromes (MDS) patients with six different DC-generating media by flow-cytometry combining expression of blast/maturation and DC antigens (DCA:CD1a,b,c, CD25, CD40, CD80, CD83, CD86, CD137-L and CD206). RESULTS: First, DCA are regularly and variably expressed on uncultured blasts/mononuclear cells (MNCs). Individual patients' DCA profiles must be evaluated before DC-culture to find suitable DCA to estimate quality/quantity of DC after culture. Second, after culture in every patient, at least one marker fulfilled these criteria. Third, different DC-generating methods showed varying efficiency to generate DC: not every method was always successful. Fourth, individual FACS-DCA profiles showed a successful DC/DC(leu) generation with at least one of three previously tested methods in every given AML/MDS case. Fifth, pooling results of all selected best methods in every given case, 28/30% DC were generated from AML/MDS samples: >60% viable DC, on average 49/56% mature DC and on average 36% of blasts were convertible to DC(leu) resulting in on average 49% DC(leu) of AML-DC. CONCLUSIONS: Individual DCA-expression profiles should be evaluated before culture to evaluate DC counts/subtypes (mature/viableDC, DC(leu)) in individual patients.

Dendritic cells (DCs) can be successfully generated from leukemic blasts in individual patients with AML or MDS: an evaluation of different methods.

Myeloid-leukemic cells (AML, MDS, CML) can be differentiated to leukemia-derived dendritic cell [DC (DCleu)] potentially presenting the whole leukemic antigen repertoire without knowledge of distinct leukemia antigens and are regarded as promising candidates for a vaccination strategy. We studied the capability of 6 serum-free DC culture methods, chosen according to different mechanisms, to induce DC differentiation in 137 cases of AML and 52 cases of MDS. DC-stimulating substances were cytokines ("standard-medium", "MCM-Mimic", "cytokine-method"), bacterial lysates ("Picibanil"), double-stranded RNA ["Poly (I:C)"] or a cytokine bypass method ("Ca-ionophore"). The quality/quantity of DC generated was estimated by flow cytometry studying (co) expressions of "DC"antigens, costimulatory, maturation, and blast-antigens. Comparing these methods on average 15% to 32% DC, depending on methods used, could be obtained from blast-containing mononuclear cells (MNC) in AML/MDS cases with a DC viability of more than 60%. In all, 39% to 64% of these DC were mature; 31% to 52% of leukemic blasts could be converted to DCleu and DCleu-proportions in the suspension were 2% to 70% (13%). Average results of all culture methods tested were comparable, however not every given case of AML could be differentiated to DC with 1 selected method. However performing a pre-analysis with 3 DC-generating methods (MCM-Mimic, Picibanil, Ca-ionophore) we could generate DC in any given case. Functional analyses provided proof, that DC primed T cells to antileukemia-directed cytotoxic cells, although an anti-leukemic reaction was not achieved in every case. In summary our data show that a successful, quantitative DC/DCleu generation is possible with the best of 3 previously tested methods in any given case. Reasons for different functional behaviors of DC-primed T cells must be evaluated to design a practicable DC-based vaccination strategy.

The role of soluble and cell-surface expressed 4-1BB ligand in patients with malignant hemopoietic disorders.

The TNFR family member 4-1BB and its ligand 4-1BBL are involved in the costimulation of T-cells and tumor-derived soluble (s)4-1BBL may influence the interaction of malignant cells with the immune system. Here, we report that cell-surface-expressed (c)4-1BBL can be expressed on mononuclear blood cells from patients with acute myeloid leukemia (AML) (n = 35), myelodysplasia (n = 5) or non-Hodgkin lymphoma (n = 11) and can be coexpressed on varying proportions of lymphoid or myeloid malignant cells and on dendritic cells differentiated from AML-blasts. Direct correlations between c- and s4-1BBL were not found in the investigated cases. Up to now expression of 4-1BBL has not been described on primary myeloid malignant cells, but only on malignant cells of lymphoid or solid tumor origin or on tumor cell lines. With our work we further contribute to the understanding of the potential role of c/s4-1BBL in immune reactions and its influence on the interaction of tumor and immunoreactive cells.