Allogeneic ALAK cells can exert suppressive effects on myeloid reconstitution and donor chimerism after BMT. B6-Ly5.2 BMC (5 × 10⁷) and ALAK cells (5 × 10⁷) from B10 or B10.D2 mice were cultured for 48 hours, as described in “Materials and methods.” (A) A fraction of cocultured cells was cultured in semisolid colony assay media in triplicate for another 7 days, as described in “Materials and methods.” (B) B6 mice were irradiated at 8.5 Gy and underwent transplantation with the cocultured cells at 3 × 10⁶ BMCs per mouse based on the cell numbers at the initiation of coculture, and the level of myeloid reconstitution was determined, as described in “Materials and methods.” (C) At day 29 after BMT, splenocytes were stained for CD45.1 expression, as described in “Materials and methods” to determine the level of donor chimerism. Statistical differences between treatment groups were determined by the unpaired t test with Welch correction. ^*Significant difference compared with the BMC-only control group. ^**Significant difference compared with H2-matched ALAK cells.