The surface expression of CXCR4, CXCR5 and CD9 was similar on peritoneal cavity CLL cells from TCL1-Tg and TCL1-Tg BAFF-/- mice (Figure 4B), ruling out this mechanism as an explanation for CLL sequestration in the peritoneal cavity in the absence of BAFF. The gene discussed is CD9; the disease is B-cell chronic lymphocytic leukemia.