CCR6 expression is acquired during the transition to mature CD19⁺CD10⁻ sIgD⁺ B-cell status and is absent during early and late stages of B lymphopoiesis in BM.

(A) Lymphoid gating of normal adult BM cells (> 90% cell viability) was based on forward and side scatter characteristics of the lymphocytes (R1). Three-parameter immunofluorescence analysis was used to detect CCR6 expression within CD19⁺ populations in this gate. (B) Plots of CD19 versus CD34 were used to gate dual-positive pro-B (R3) and CD34⁻CD19⁺ cells (R2), a population that includes immature and mature B cells. (C) Plots of CD19 versus CD10 were used to discriminate between dual-positive immature B cells (R5) and CD19⁺CD10⁻ mature B cells (R4). These gated cells were then plotted for CD19 versus CCR6 (D-G). Data with PE-labeled anti-CCR6 and isotype-matched IgG₁ control MoAbs are shown. For each population, the threshold of positivity was placed according to the nonspecific binding of control IgG. Populations corresponding to early pro-B and immature B cells and their respective percentage values within total BM cells are given in panels B and C, respectively. One representative example of 5 samples from different BM donors is shown.