VSSP induces differentiation of tumor-promoted MDSCs towards DCs in vitro . Highly purified MDSCs from the spleen of EL4 TB mice were incubated for 24 h with VSSP. (A-B) Expression of CD11c, CD11b, CD40 and CD86 was evaluated by FACS within the CD11b+Gr1+ gate. (C-D) Inhibition of T cell proliferation was assessed by the culture of 40% in vitro-treated MDSCs with splenocytes from naive mice in the presence of Con A. (C) Effect of VSSP on the functional activity of MDSCs induced by EL4 and MCA203 tumors. (D) MDSCs from EL4 TB mice were also cultured in vitro with polyI:C or LPS and their suppressive activity was compared with VSSP-treated MDSCs. ANOVA and Tukey’s tests were employed for statistical comparison. These experiments were repeated three times with similar results.