TCR Vβ analysis of precultured BMMCs and the derived 13-day culture from patient 1. Cytofluorimetric analysis of 6 Vβ families in BMMCs and the derived p190BCR-ABL–stimulated 13-day culture are shown. The presence of expanded populations within Vβ 1, Vβ 2, Vβ 5.1, Vβ 6.7, and Vβ 13 demonstrates polyclonality of the response driven by the antigen.