CD19 and acute lymphoblastic leukemia: Moreover, the surface antigens of BM-MSCs derived from different diseases (i.e., ALL and AA) were similar detected by FCM, showing that both types of MSCs were positive for CD90, CD29, CD105, and CD166 and negative for HLA-DR, CD34, CD45, and CD19, respectively (Fig. 1B-1, B-2), which indicated that both types of MSCs expressed typical mesenchymal surface markers.