CIA-derived PMN-MDSCs’ effects on TNF-𝛂 expression, proliferation and apoptosis of B cells
To verify the regulatory role of PMN-MDSCs on B cells, we cocultured B cells with PMN-MDSCs, finding that TNF-𝛂+B cells (Fig. 4A) and Ki67+ B cells (Fig. 4B) increased in the presence of PMN-MDSCs. And the enhancing effects increased with increasing ratio of PMN-MDSCs to B cells (Fig. 4E, 4F). The supernatants of the coculture medium had higher IgG (Fig. 4C) and TNF-𝛂 (Fig. 4D) concentration compared with B cells alone. In addition, PMN-MDSCs decreased B cells’ apoptosis in vitro (Fig. 4G, 4H). The coculture assay demonstrated that PMN-MDSCs played supporting role to B cells. We further explored the difference of CIA and DBA/1J mice derived PMN-MDSCs’ effects on B cells, finding that PMN-MDSCs derived from DBA/1J mice had weaker or even no modulatory ability compared to the counterparts of CIA mice (Fig. 4I-4K).