The BTLA and PD-1 signaling pathways independently regulate the proliferation and cytotoxicity of human peripheral blood γδ T cells

Background: B- and T-lymphocyte attenuator (BTLA) and programmed cell death-1 (PD-1) inhibit gamma delta T cell homeostasis and activation. This study aimed to determine whether BTLA and PD-1 signaling pathways were convergent or independent in human peripheral blood gamma delta T cells. Herein we demonstrate that the signalings of BTLA and PD-1 regulated proliferation and cytotoxicity of human gamma delta T cells, respectively. Methods: Human peripheral blood gamma delta T cells were cultured with inactivated Jurkat cells in the presence of interleukin-2 and zoledronate (Zol) for 14 days. Flow cytometry was performed to evaluate the phenotypes and functions of gamma delta T cells. Results: The proliferation of the gamma delta T cells was increased when PBMCs were cocultured with inactivated herpes virus entry mediator (HVEM)(low) Jurkat cells. The cytotoxicity of the expanded gamma delta T cells was not affected by coculture with inactivated HVEMlow Jurkat cells and was further increased in the presence of anti-PD-L1 mAb. These results suggest that the inactivation of the BTLA signaling pathway during expansion could help produce more gamma delta T cells without compromising gamma delta T cell function. The inhibition of BTLA or PD-1 signaling repressed phosphorylation of the src homology region 2-containing protein tyrosine phosphatase 2 and increased the phosphorylation of protein kinase B in gamma delta T cells. However, there were no synergistic or additive effects by a combination of BTLA and PD-1 blockade. Conclusion: These results suggest that BTLA signaling is crucial in regulating gamma delta T cell proliferation and function and that the BTLA and PD-1 signaling pathways act independently on the proliferation and cytotoxicity of human peripheral gamma delta T cells.