Plasma-cell differentiation is generally accompanied by the up-regulation of CXCR4 expression. Sorted CXCR4^- peripheral blood B cells were stimulated with IL-2, IL-10, and CD40L (left), CpG 2006 (middle), or S aureus Cowan I (SAC, right). Histogram plots show CXCR4 expression of CXCR4^- sorted B cells before culture (day 0, thin line) and CXCR4 expression of CD19⁺ B cells and CD38⁺⁺/CD20^- plasma cells at day 3 and day 8 (bold line). Shown is a representative result of 3. Values at top right indicate the percentage of CXCR3-expressing CD19⁺ and CD38⁺⁺/CD20^– cells, respectively, compared with CXCR4–-sorted cells.