FACS analysis of CD4⁺ and CD8⁺ T-cell subsets before and 1 year after allo-BMT. FACS profiles are given for BLS patients 1 (top) and 2 (bottom) and their respective BM donors, after labeling of PHA/rIL-2–stimulated CD4⁺ and CD8⁺ T-cell subsets with MoAb W6/32 directed against MHC class I and subsequent staining with fluorescein (FITC)-conjugated goat anti-mouse MoAb or after a direct staining with an FITC-conjugated MHC class II–directed MoAb (BD -HLA-DR); GAM-FITC was used as a negative control.