RTFI of SCID-hu mice with MM^GFP+ lesions within human fetal bone. (A) Flow cytometric analysis indicates an approximate 2-log difference in mean fluorescence intensity of INA-6^GFP+ cells (green peak) versus the parental INA-6 cells (black peak). (B-E) Microscopic analysis of INA-6^GFP+ cells transduced with the GFP construct. Panels B and C refer to GFP^- cells; panels D and E refer to GFP⁺ cells analyzed by either contrast-phase (B,D) or fluorescence microscopy (C,E) (original magnification × 100). (F) Representative imaging of 6 different SCID-hu mice following engraftment of INA-6^GFP+ cells (2.5 × 10⁶) into the human fetal bone (indicated by yellow arrows). (G-H) Serial sections of a human fetal bone engrafted with INA-6^GFP+ cells. H&E staining (G) and fluorescence microscopy (H; original magnification ×200). (I-K) Dexamethasone, Atiprimod, and B-B4-DM1 treatments of SCID-hu mice engrafted with INA-6 cells; levels of shuIL-6R in SCID-hu mice sera were analyzed. The blue arrows indicate the day of treatment. (L) Images of a representative SCID-hu mouse bearing INA-6^GFP+ lesions in human fetal bone before and after 2 consecutive days of treatment with B-B4-DM1 (150 μg DM1/kg intravenously). Fetal bone image enlargements are shown.