Pax5^−/− huPax5 pro-/pre-B-cell clones 16 and 20 can be induced to develop into biphenotypic cells if they express low levels of huPax5 after high-level doxycycline induction in vivo. (A) Experimental overview: Pax5^−/− huPax5 pro-/pre-B-cell clones 16 and 20 (all Ly5.2⁺) were transplanted into sublethal γ-irradiated Rag2^−/−/Ly5.1⁺ hosts that were fed with doxycycline (0.2 g/L) in the drinking water 1 week after transplantation for the next 15 weeks. (B) Representative FACS analysis of 2 individual experiments (n = 3) of Ly5.2⁺ bone marrow cells for B220, CD19, and CD11b surface expression 2 weeks after transplantation. The numbers represent percentages of cells. Almost no Ly5.1⁺ and B220⁺/CD19⁻/CD11b⁺ biphenotypic cells were found 2 weeks after transplantation in the bone marrow of Rag2^−/−/Ly5.1⁺ hosts. (C) Summary of the frequencies and total cell numbers of Ly5.1⁺ and B220⁺/CD19⁻/CD11b⁺ biphenotypic cells 2 weeks after transplantation detected in the bone marrow of Rag2^−/−/Ly5.1⁺ hosts. Circles represent individual mice. (D) Representative FACS analysis of 2 individual experiments (n = 3) of Ly5.2⁺ bone marrow cells for B220, CD19, and CD11b surface expression 2 weeks after transplantation. The numbers represent percentages of cells. High numbers of Ly5.1⁺ and B220⁺/CD19⁻/CD11b⁺ biphenotypic cells were found 16 weeks after transplantation in the bone marrow of Rag2^−/−/Ly5.1⁺ hosts. (E) Summary of the frequencies and total cell numbers of Ly5.1⁺ and B220⁺/CD19⁻/CD11b⁺ biphenotypic cells 16 weeks after transplantation detected in the bone marrow of Rag2^−/−/Ly5.1⁺ hosts. Circles represent individual mice.