From experience, I have seen that prednisone causes a false rise in WBC's (leukocytosis).
So, I would not be concerned if his WBCs went down when it was discontinued.
52 yo female, dx 9/08, AA/hypo-MDS, subclinical PNH, ATG/CsA 12/08, partial response. Tried slow cyclosporine taper over 4+ years. Platelets fell, so back on cyclosporine. Trisomy 6 clone in 5% of cells.