B-cell reconstitution by transplantation of B220 CD117 B-lymphoid progenitors into irradiated mice.

Bone marrow cells of 4-week-old CBA/J mice were searched for progenitors that can reconstitute CBA-type B lineage (B220+) cells after transplantation into irradiated (BALB/c x CBA/J) F(1) mice. In recipients of B lineage-committed B220+ CD117+ cells, which were CD19+ CD127+ CD25- IgM-, numbers of CBA-type B220+ cells had increased greatly by day 8 after transplantation. This increase stopped by day 10 but cell numbers remained at this level for at least 8 weeks. B-cell production in the bone marrow of B220+ CD117+ cell recipients occurred even 8 weeks after transplantation. Probably, the transplanted B-lymphoid progenitors are capable of self-renewing up to 8 weeks after transplantation. B lineage- uncommitted CD117high CD71- cells, which were B220- and included haematopoietic stem cells, could also reconstitute B lineage bone marrow cells after transplantation. Sequential development of CD117+, CD25+ and IgM+ cells in CBA-type B220+ bone marrow cells occurred 2-4 days faster in recipients of B220+ CD117+ progenitors than in recipients of CD117high CD71- progenitors, suggesting that the development of the former progenitors from the latter may take 2-4 days.