The Effect of G-CSF Mobilization on the Expression of Immunoregulatory-Associated Molecules and G-CSFR Gene in the Peripheral Blood γδ⁺ T Cells

Background Granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood stem cell has been used more frequently than bone marrow as the source of stem cells in allogeneic hematopoietic stem cell transplantation. Although it contains more mature T cells, neither the incidence nor the severity of acute graft-versus-host disease (aGVHD) is higher compared with bone marrow transplantation. This might be due to the immunoregulatory effects of G-CSF on T cells, including that G-CSF directly modulated via its receptor on T cells or indirectly modulated T cell immune responses via effector cells and cytokines. Recent studies have shown that γδ⁺ T cells have immunoregulatory function, and might also participate in the pathogenesis of GVHD. However, these mechanisms are not fully understood, and whether G-CSF could influence the immunoregulatory-associated gene expression of γδ⁺ T cells remains unknown. The aim of this study is to investigate the effect of G-CSF mobilization on the expression of immunoregulatory-associated molecules and G-CSFR gene in the peripheral blood γδ⁺T cells.

Methods Peripheral blood γδ⁺ T cells were sorted by magnetic activated cell-sorting system. The expression levels of immunoregulatory- associated molecules (Foxp3, CD25, CTLA-4, GITR, TLR8, STAT-1, STAT-3 and RORc) and G-CSFR gene were analyzed in peripheral blood γδ⁺ T cells from 10 donors before and after G-CSF mobilization, using real-time reverse transcription polymerase chain reaction with SYBR Green I staining. The β₂-microglobulin gene was used as an endogenous reference, and the relative mRNA expression level of each gene was evaluated by the 2^-ΔCt×100% method.

Results The expression levels of Foxp3, CD25, CTLA-4 and GITR genes in peripheral blood γδ⁺ T cells were similar before and after G-CSF mobilization (P=0.827, P=0.667, P=0.053 and P=0.129). The expression level of TLR8 gene in peripheral blood γδ⁺ T cells after G-CSF mobilization (0.731% ± 0.350%) was significantly higher than that before mobilization (0.188% ± 0.176%) (P=0.001). The expression level of STAT-1 gene in peripheral blood γδ⁺ T cells did not differ significantly before and after G-CSF mobilization (P=1.000), while the expression levels of STAT-3, RORc and G-CSFR genes in peripheral blood γδ⁺ T cells after mobilization (0.536% ± 0.234%, 0.683% ± 0.250%, 8.208% ± 6.175%) were significantly higher than that before mobilization (0.243% ± 0.134%, 0.356% ± 0.179%, 1.947% ± 1.442%) (P=0.003, P=0.003 and P=0.007).

Conclusions G-CSF mobilization might increase the expression levels of TLR8, STAT-3, RORc and G-CSFR genes in peripheral blood γδ⁺T cells.

The result suggested that G-CSF might play the role of immunoregulation by affecting γδ⁺ T cells.