Growth of HB-1 cells on hematopoietic supportive stromal cells. (A) HB-1 cells were cultured on hematopoietic supportive stromal cells, MS-10 (▴) or hematopoietic nonsupportive stromal cells, MS-K (▪). The number of HB-1 cells in suspension was counted every day. Data represent mean ± SE. (B) HB-1 cells were cultured on MS-10 cell layer, but separated by Millicell-HA membrane (▴) or cultured in the presence of conditioned medium of the coculture (•). HB-1 cells were directly cultured on MS-10 cells as control (▪). The number of HB-1 cells was counted every day. Data represent mean ± SE.