Surface CCR7 and CXCR4 expression. (A) Surface CCR7 expression is increased on CLL B cells when compared with healthy PB B cells, and ZAP-70⁺ CLL B cells have a significantly higher surface expression than ZAP-70^– CLL B cells. CLL PB B cells have a 5- to 7-fold higher level of surface CCR7 expression than control PB B cells (Student t test; **P < .001). ZAP-70⁺ CLL B cells have a significantly higher CCR7 expression than ZAP-70^– cells (*P = .009). The n numbers are shown in parentheses. Isotype control antibodies staining MFI mean ± SEM; 0.3 ± 0.03. (B) Surface CXCR4 expression is significantly increased on CLL B cells compared with B cells from healthy controls. CXCR4 MFI for ZAP-70⁺ CLL B cells (n = 12), ZAP-70^– CLL B cells (n = 9), and control PB B cells (n = 6). The MFI of both ZAP-70⁺ and ZAP-70^– CLL samples differs significantly from the control PB B-cell MFI (Student t test; *P < .05). There was no significant difference between the CXCR4 MFI of ZAP-70⁺ and ZAP-70^– CLL cells (P = .53).