CXCR4 and diffuse large B-cell lymphoma: To assess the impact of rituximab on the level of surface-expressed CXCR4, four DLBCL cell lines were exposed to two doses of rituximab (1.04 μg/ml, 8.33 μg/ml) for 24 and 48 hours before flow cytometry-based analysis was conducted (Figure 4).