Preferential inhibition of trisomy 8 cell colony growth related to suppression of growth by Vβ subfamily expanded CD8⁺ cells. Autologous column-purified CD4⁺ or CD8⁺ cells were incubated with 3 BMMC aliquots for 4 hours and placed in semisolid media for short-term culture in an additional 3 patients. Suppression of trisomy 8 progenitor–derived cell growth is seen for the BM cells previously incubated with CD8⁺ cells only (A). Similar experiments performed with Vβ-selected CD8⁺ cells (B) from an additional 7 patients showed preferential inhibition by selected, but not unselected, cells of trisomy 8 but not karyotypically normal cells. Erythroid and myeloid cells were affected.