Fig. 3

BMSCs regulated NK cell function through the TIGIT/CD155 pathway. A. NK cells were tested in freshly isolated cells, after 6-day cultured in 100 U/mL IL-2 and after 6-day co-cultured with BMSCs for the expression of NK cell surface activating receptors. *indicates a significant difference compared with the NK cell group, P < 0.05. & indicates a significant difference compared with the IL-2 NK cell group, P < 0.05. B. The morphology of BMSCs under the microscope (scale bar: 100 μm). C. Expression of typical markers with CD73, CD90, CD105, CD34, and CD45 of BMSCs. All the BMSCs used in subsequent experiments were third‐generation. D. Flow cytometry detection of CD155/CD112/CD113 expression levels on the surface of BMSCs. The expression of CD155 on BMSCs of MDS patients was significantly increased, but CD112 and CD113 were expressed at very low levels. E. Experimental procedure of co-culture of BMSCs and NK cells F. The morphology of the BMSCs-NK co-culture system under the microscope (scale bar: 100 μm). G. Expression of activating receptors NKG2D, NKp30, NKp44, and CD69 was measured by flow cytometry after blocking TIGIT and CD226 mAb. Data were expressed as MFI. H. Cytokine levels secreted by NK cells after blocking TIGIT and CD226 mAb. I. Results of cytotoxicity of NK cells in which NK cells were used as targets while SKM-1 cells were used as effectors. The apoptosis of SKM-1 cells gradually increased after the addition of TIGIT mAb and CD226 mAb. Data were expressed as a percentage of lysis. *indicates a significant difference compared with the PBS group. #indicates a significant difference compared with the TIGIT mAb and CD226 agonist groups, P < 0.05. BMSCs, bone marrow mesenchymal stem cells; NK, natural killer; TIGIT, T cell immunoglobulin and ITIM domain; MFI, mean fluorescence intensity; PBS, phosphate-buffered saline