FL CMPs have limited B-lymphoid differentiation potential.

(A) CD45.2⁺ FL CMPs (1 × 10⁴) were competitively transplanted with 5 × 10⁵CD45.1⁺ WBM cells into lethally irradiated CD45.1⁺ hosts. Splenocytes were harvested at 3 weeks after transplantation and were analyzed for donor-derived B and T cells. FL CMPs gave rise to no T-cell progeny (not shown) but showed minor production of B cells. Myeloid progeny derived from FL CMPs were largely absent from the spleen by this time. (B) Limiting-dilution analysis of B-lymphoid differentiation potential from FL CMPs. Graded numbers of FL CMPs were deposited into irradiated OP9 stromal cultures that were supplemented with IL-7 and SLF. One in 160 FL CMPs generated B-cell progeny in this assay.