Recipient cells after syngeneic transplantation of eGFP⁺ cells at the time of maximal colonization (magnification ×40; scale bars represent 50 μm). (a, b): BM cells: (a) differential interference contrast (DIC) microscopy and (b) fluorescence image: green: eGFP⁺ cells, orange: immunofluorescence staining with phycoerythrin- (PE-) coupled antibodies showing CD117 (hematopoietic progenitor’s marker) expression on host cells. (c, d) Spleen cells: (c) DIC and (d) fluorescence image: green: eGFP⁺ cells, orange: immunofluorescence staining with phycoerythrin- (PE-) coupled antibodies showing CD45R/B220 (B lymphocyte marker at all stages) expression on donor and host cells.