Relative frequencies and mitotic activity of B-lineage precursors in BM do not change during adult life.

(A) The incidences of pro B cells (CD34⁺CD10⁺CD19⁺), pre-B cells (CD19⁺sIgM⁻cμ⁺), immature B (IgM⁺CD24^hiCD10⁺IgD⁻), naive B (IgM⁺CD24^hiIgD⁺CD38^+/−), and mature B (IgM⁺CD24^loIgD⁺CD38⁻) cells were determined by flow cytometry and shown as percentages of total viable CD19⁺ lymphocytes (%) ± SDs. (B) Expression of the Ki-67 nuclear proliferation antigen was determined by flow cytometry, using low-angle light scatter to resolve large and small lymphocytes. The data represent average percentages of pro-B cells (CD34⁺CD19⁺) and pre-B cells (CD19⁺sIgM⁻cμ⁺) ± SDs. Differences between groups were not statistically significant (P > .05).