We then examined a potential direct role for MDSC-associated IDO as a driver of Breg differentiation in co-cultures of immune sorted MDSCs (CD11b+Gr-1+) from splenocytes and tumors of tumor implanted WT and IDO-/- mice with CD19+ purified B cells in 5:1 ratio (5 B cells: MDSC) (Figures 2A, B). The gene discussed is IDO1; the disease is neoplasm.