Mll-AF4 marrow progenitor cells expressed myeloid and lymphoid markers (B220, CD43, and CD11b) when grown under pro-B lymphoid conditions. (A) Colonies from young (5- to 8-week-old) mice. Bone marrow cells from wild-type (n = 8), Mll-AF4 (n = 7), and Mll-AF9 (n = 8) mice were plated in methylcellulose medium under lymphoid conditions for 3 generations. The error bars represent SEMs. (B) Representative results of multiparameter FACS analysis on pooled cells from the methylcellulose culture of the third generation under lymphoid conditions.