yeloid-derived Suppressor Cells Inhibit Proliferation and Killing Activity of Neuroblastoma Antigen-specific Cytotoxic T Lymphocyte in vitro

Objective To explore the inhibitory role of myeloid-derived suppressor cell (MDSC) in the proliferation and killing activity of neuroblastoma antigen-specific cytotoxic T lymphocyte (CTL) in vitro.

Methods The neuroblastoma antigen specific CTLs were successfully prepared on the basis of cultivation of neuroblastoma SK-N-SH cells and separation of BALB/c mice myeloid-derived dendritic cell (DC) and CD3⁺T cells in vitro. MDSCs were purified and cultivated with CTLs, then the inhibitory role of MDSC in the proliferation of CTL was detected by fluorescence staining of 5, 6-carboxyfluorescein diacetate succinimidyl ester (CFSE) and flow cytometry. Furthermore, CTL, SK-N-SH and MDSC were mixed and cultivated, the killing rate of CTL on SK-N-SH and the secretion of IL-2, IFN-γ in supernatant of the different groups were detected by ELISA.

Results After magnetic cell sorting, the rate of Gr-1⁺CD11b⁺MDSC reached to 84.6% by flow cytometry test. The levels of IL-2 and IFN-γ in supernatant of antigen-loaded CTLs were significantly higher than those in supernatant of T cells (P < 0.05). The proliferation of CTLs cultivated with MDSC was significantly inhibited, with strong fluorescence in view: however, CTLs cultivated alone proliferated obviously, with weak fluorescence intensity. The killing rate of CTLs to SK-N-SH in MDSC+CTL+SK-N-SH group was significant lower than that in CTL+SK-N-SH group (t=6.506, P < 0.001). Significant difference existed in the secretion levels of IL-2 and IFN-γ in the supernatant between the two groups (all P < 0.01).

Conclusion MDSC inhibite the proliferation and activity of neuroblastoma antigen-specific CTLs in vitro result in immune tolerance and reduced the killing effect of CTL on neuroblastoma cells.