Figure 2.

Flow cytometric analysis of

(a) B220 and CD43, IgM, CD25, c-kit, or CD19 and CD25 on bone marrow cells from three IL-2^−/− mice (IL-2^−/− no. 1, specific pathogen-free 26-weeks old; IL-2^−/− no. 2, germ-free 23-weeks old; IL-2^−/− no. 3, germ-free 23-weeks old) and one IL-2^+/+ mouse (germ-free; 24-weeks old) or (b) B220 and IgM on spleen cells from the same mice. *Represents B-lineage cell fractions A, B, and C that contain pro-B and pre-BI cells; **represents B-lineage cell fraction D that contains pre-BII cells; ***represents B-lineage cell fraction E that contains immature B cells prepared to exit the bone marrow. These fractions have been described previously by Hardy et al.¹⁵