Bone marrow (BM) cells are considered the source of stem cells for various organs. However, how quickly BM cells can penetrate and constitute lymphoid organs remains elusive. In the present study, scientists addressed this issue in a model using genetically-labeled syngeneic BM transplantation (BMT).

For this experiment donor BM cells were obtained from "green mice", transgenic mice with enhanced GFP. Lethally irradiated C57BL/6 mice were infused with 1 × 10⁶ BM cells from the green mice through the tail vein.

BM chimerism was analyzed by FACS and the presence of donor BM cells in thoracoabdominal organs was assessed by fluorescence microscopy. The commitment of BM cells was examined by immunohistochemical staining using epithelium-, macrophage-, B and T-lymphocyte, and endothelium-specific antibodies. The study results show that BM chimerism reached 40±18.5%, 82.6±23.4%, and 72±18% (mean ± SD) at 1, 4, and 12 weeks after BMT, respectively.

GFP-positive cells were detected in all organs in the course of chimeric formation. Most GFP-positive cells were T and B lymphocytes in lymphoid systems including spleen, thymus, mesenteric lymph nodes and microvilli, and some were positive for macrophage and endothelial cell markers.

Experimental data indicate that BM-derived cells migrate rapidly into various thoracoabdominal organs after BMT, and that lymphoid tissues are predominantly replaced with infused BM in lethally-irradiated mice.