Granulocyte Colony-Stimulating Factor Mobilization Affects The Expression Of Regulatory γδ T Cells

The immune modulatory effect of granulocyte colony-stimulating factor (G-CSF) on T cells resulted in an unexpected low incidence of graft-versus-host disease (GVHD) in allogeneic peripheral blood stem cell transplantation. Our previous studies demonstrated that G-CSF mobilization influenced the distribution and clonality of TRGV and TRDV repertoire (T cell receptors of γδ T cells), and significant positive correlation was observed between the invariable clonality of TRDV1 gene repertoire after G-CSF mobilization and low incidence of GVHD in recipients (P=0.015, OR=0.047) (Li Xuan et al. Journal of Translational Medicine 2011). Regulatory γδ T cells (γδ Tregs), which express Foxp3 and primarily belong to CD27⁺CD25^high phenotype, are a novel subset of cells with immunosuppressive function (Xiaoyan Li et al. Journal of Immunology 2012). However, whether G-CSF could influence the expression of γδ Tregs remains unknown. The aim of this study was to investigate the effect of G-CSF mobilization on the expression of γδ Tregs.

The immunophenotyping of γδ Tregs was analyzed in peripheral blood mononuclear cells (PBMCs) from 20 donors before and after G-CSF mobilization, using flow cytometry.

Compared with that before mobilization, the proportions of Vδ1 and CD25⁺ subsets were significantly increased (P=0.012, P=0.032), whereas the Vδ2 proportion was significantly decreased after G-CSF mobilization (P=0.002). The proportions of total γδ T cells, CD27⁺ and Foxp3⁺ subsets were similar between the two groups (P=0.133, P=0.110, P=0.780, respectively). In addition, there was a significant increase in the proportions of Foxp3⁺Vδ1 and CD25⁺Foxp3⁺ subsets (P=0.038, P=0.013), and a significant decrease in the proportions of CD27⁺Vδ2 and CD25⁺Vδ2 subsets after G-CSF mobilization (P=0.013, P=0.022). The proportions of CD27⁺γδ T, CD25⁺γδ T, Foxp3⁺γδ T, CD25⁺CD27⁺, CD27⁺Foxp3⁺, CD27⁺Vδ1, CD25⁺Vδ1 and Foxp3⁺Vδ2 subsets were similar before and after G-CSF mobilization (P=0.422, P=0.342, P=0.724, P=0.070, P=0.503, P=0.053, P=0.386 and P=0.097, respectively). We then compared the Foxp3, CD27 and CD25 phenotypes in total γδ T cells, Vδ1 and Vδ2 subsets. We observed a significant increase in the proportion of CD27⁺Foxp3⁺ Vδ1 subsets after G-CSF mobilization (P=0.036). The proportion of CD27⁺Foxp3⁺γδ T and CD27⁺Foxp3⁺Vδ2 subsets before mobilization were similar to that after mobilization (P=0.539, P=0.507). The proportion of CD25⁺Foxp3⁺γδ T, CD25⁺Foxp3⁺ Vδ1, CD25⁺Foxp3⁺Vδ2, CD25⁺CD27⁺γδT, CD25⁺CD27⁺Vδ1 and CD25⁺CD27⁺ Vδ2 subsets were also similar between the two groups (P=0.249, P=0.539, P=0.507, P=0.934, P=0.209 and P=0.061, respectively).

G-CSF mobilization significantly increased the proportions of Vδ1 subsets, including Foxp3⁺Vδ1 and CD27⁺Foxp3⁺ Vδ1 subsets, whereas decreased the Vδ2 proportion.

Li:This work was supported by Grants from National Natural Science Foundation of China (30871091 and 91129720), the Collaborated grant for HK-Macao-TW of Ministry of Science and Technology (2012DFH30060), the Guangdong Science & Technology Project (2012B0506: Research Funding. Liu: It was supported by 863 Program (No. 2011AA020105).: Research Funding; It was supported by National Public Health Grand Research Foundation (Grant No. 201202017), National Natural Science Foundation of China (Grant No.81000231, No.81270647).: Research Funding; It was supported by Science and Technology Program of Guangzhou of China (11A72121174).: Research Funding.