Flow-cytometric analysis of chemokine receptor expression. (A) Chemokine receptor expression on normal and myeloma PCs. The mean expression level and range is shown. (B) CCR2 expression is significantly lower on CD19^- PCs from MGUS patients than that on CD19⁺ PCs from the same bone marrow. The figure shows 5th, 25th, 50th, 75th, and 95th percentiles for expression, measured as mean fluorescence intensity.