HPCs populate lymphoid tissues. Histologic cryosections of the spleen, liver, and thymus were stained for GFP using an anti-GFP monoclonal antibody and examined under the Multi photon/confocal microscope. (A) GFP-expressing cells could be detected in both spleen and liver early after HPC transplantation, diminishing in the liver with time. Scale bars represent 50 μm. (B) GFP-positive cells remained detectable in the thymus 56 days after transplantation. At each time point, n ≥ 3 mice. Scale bar represents 50 μm.