This study was aimed to investigate the difference of immunological properties between recombination human granulocyte colony-stimulating factor (rhG-CSF) mobilized peripheral blood grafts (G-PB) and rhG-CSF primed bone marrow grafts (G-BM). The lymphocyte proliferation ability and the quantities of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) secreted by T cells were determined by using MTT assays and sandwich ELISA; T cell subgroups, dendritic cells (DC), monocytes and the expression of CD28 costimulatory molecules on T cells were determined by multicolor flow cytometry. The results showed that the absolute numbers of lymphocytes, monocytes, CD3+, CD4+ and CD8+ T cells as well as DC1 and DC2, the ratios of CD4/CD8 in G-PB were significantly higher than those in G-BM, respectively (P < 0.001). T cell proliferation ability was significantly higher in G-PB than that in G-BM (P < 0.05). The quantities of IFN-gamma and IL-4 secreted by T cells per microliter of G-PB was significantly higher than those of G-BM, the ratios of IL-4/IFN-gamma were significantly lower in G-PB than that in G-BM (P < 0.001). As compared with G-BM, the ratio between DC2 and T-lymphocyte was significantly low in G-PB (P < 0.01), whereas the percentage and overall expression of CD28 on CD4+ and CD8+ cells were significantly high in G-PB (P < 0.05). It is concluded that T cell hyporesponsiveness of G-PB and G-BM induced by rhG-CSF in vivo were confirmed to be different, and the difference of immunological properties between G-PB and G-BM may explain the lower incidence of GVHD and lower relapse after G-BM and G-PB transplantation respectively.