Petra Vidláková

Generation of antigen-loaded dendritic cells in a serum-free medium using different cytokine combinations

Dendritic cells (DCs) are antigen-presenting cells that play a critical role in the induction of cytotoxic T-lymphocytes. An optimal method for the generation of DC for clinical use remains to be established. The aim of our study was to find an optimal cytokine combination for DC generation from peripheral blood stem cells (PBSC) and peripheral blood mononuclear cells (PBMC) in serum-free conditions. Serial immunophenotyping enabled us to observe changes in DC content during the culture as well as the development of maturation and activation markers. As a source for DC culture, we used PBSC from patients with multiple myeloma after stem cell mobilization using cyclophosphamide and G-CSF, or PBMC from healthy donors without mobilization. The cells were cultured in a serum-free medium with different cytokine combinations including GM-CSF, TNF-alpha, Flt-3, CD40L, IFN-gamma, IL-1alpha, IL-6, PGE1, and IL-4. The cell cultures were evaluated by immunophenotyping. For PBMC, interleukin-12 assay was performed. For PBSC, the yield of DC as determined by CD83+ cell count ranged from 0. 6 x 10(5) to 30.1 x 10(4) (mean: 9.4 x 10(4)) of DC generated per 1 x 10(6) of initially plated nucleated cells from apheresis. This yield corresponded to (0.3-19.1) x 10(5) (mean: 4.3 x 10(5)) per 1 x 10(6) of CD34+ cells in the apheresis products. For PBMC, the yield was (0.4-24.8) x 10(4) (mean: 2.4 x 10(4)) of DC generated per 1 x 10(6) of initially plated mononuclear cells from venous blood. The cultured cells expressed the mature immunophenotype. No significant differences in cell yield or immunophenotype were detected when comparing different cytokine combinations.

Selective Depletion of Alloreactive T Cells and Study of Anti-Tumor Activity of Specific T Cell Clones in Patients with Leukemia and Renal Carcinoma

BACKGROUND Graft-versus-host disease (GVHD) is a severe complication of allogeneic transplantation of hematopoietic stem cells. Donor T cells play a major role in GVHD leading to the host tissue damage, mainly the skin, liver, and gastrointestinal tract. A selective depletion using an anti-CD25 immunotoxin can eliminate harmful alloreactive T cells while preserving other donor T cells with antileukemic and antiinfectious reactivity. PATIENTS AND METHODS We performed 15 mixed lymphocyte reactions with clinical specimens from 12 patients with various types of leukemia (7x AML, 3x ALL, 1x CML, 1x CLL) and PBMC from 15 healthy volunteers from Transfusive station FN Brno Bohunice. RESULTS In our experiments we have demonstrated, that antileukemic (GVL) effect of donor, especially CD4+ T cells was well preserved (7.46%), while unfavourable alloreactive (GVH) reaction of donor T cells was completely removed. The graft-versus-host (GVH) reactivation of donor cells was negligible ever after repeated stimulation with irradiated patients PBMC. CONCLUSION We have shown that anti-CD25 immunotoxin (IT), RFT5-SMPT-dgA, launched against alpha chain for human interleukin 2 (IL-2), led to long-term selective depletion of alloreactive donor T cell clones while their antileukemic activity was well preserved. Base on our results the clinical phase I/II study was designed. This study was initiated in year 2007 in three clinical centers in Czech Republic.