Maintaining hyporesponsiveness and polarization potential of T cells after in vitro mixture of G-CSF mobilized peripheral blood grafts and G-CSF primed bone marrow grafts in different proportions

Background and objectivesGranulocyte colony-stimulating factor (G-CSF) primed bone marrow grafts (G-BM) plus G-CSF mobilized peripheral blood grafts (G-PB) were used successfully in haploidentical transplantation and the incidence of graft-versus-host disease (GVHD) was not higher compared with that in patients with HLA-matched donors. The immunological characteristics of T cells in G-BM and G-PB mixed in vitro in different proportions were investigated.Design and methodsLymphocyte proliferation ability, interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) secreted by T cells were determined using a monotetrazolium (MTT) assay and sandwich enzyme-linked immunosorbent assay (ELISA), respectively. T cell subgroups, dendritic cells (DC) subsets, and monocytes were analyzed using flow cytometry in steady-state bone marrow (SS-BM), G-PB, and G-BM and calculated in mixture grafts.ResultsThe quantities of IFN-gamma and IL-4 secreted by lymphocytes per microliter in the three mixture grafts were 2- to 4-fold lower than in G-PB and 1- to 3-fold higher than in SS-BM and G-BM, while the IL-4/IFN-gamma ratio was higher than SS-BM and G-PB and lower than G-BM, although no significant difference was confirmed. Lymphocyte proliferation ability in the three mixture grafts was comparable to G-BM and significantly lower than SS-BM and G-PB. Lymphocytes, monocytes, T cell subsets, and DC subsets were 2- to 8-fold lower than in G-PB and 2- to 22-fold higher than in SS-BM and G-BM. The DC1/DC2 ratio was significantly higher in SS-BM than G-PB, G-BM, and the three mixture grafts (P < 0.05).Interpretation and conclusionsOur results suggest that T cell hyporesponsiveness and polarization of T cell from Th1 to Th2 could be maintained after in vitro mixture of G-PB and G-BM in different proportions.