Submitted July 1, 2002
Accepted January 31, 2003
Host stem cells can selectively reconstitute missing lymphoid lineages in irradiation bone marrow chimeras
Amariliz Rivera, Chiann-Chyi Chen, Joseph P Dougherty, Avraham Ben-Nun, and Yacov Ron*
Molecular Genetics, Microbiology and Immunology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ, USA
Immunology, The Weizmann Institute of Science, Rehovot, Israel
* Corresponding author; email: yron{at}umdnj.
The regulatory elements governing the process of lymphopoiesis from pluripotential stem cells to mature lymphocytes are not well understood. In this study we found that in bone marrow chimeras made by reconstituting lethally irradiated normal mice with bone marrow taken from genetically B cell-deficient animals (µMT.B6 
F1) the B cell compartment is reconstituted with host-derived B cells. Similarly, animals reconstituted with bone marrow taken from mice with genetic deficiencies in the development of T cells (TCR-/- F1) or both B and T cells (RAG-/- F1), the missing lymphocyte lineage(s) were specifically reconstituted from host-derived cells. In all chimeras, all other blood lineages were generated from donor-derived stem cells. Control chimeras (B6 F1) had only donor-derived hematopoietic cells as expected. The reconstituted, host-derived lymphoid compartments contained normal functional cell populations as determined by the presence of T cells expressing all 16 common TCR V
families, and the presence of all antibody isotypes in the serum. Reconstituted TCR-/- F1 chimeras were also able to mount T cell proliferative responses to foreign antigens equal to that of control animals. This observation would seem to suggest that during lymphpoietic reconstitution, missing lymphoid lineages can dictate their own reconstitution.
