Inhibition of human CXCL13-mediated internalization of human CXCR5 receptor. Human pre-B-697-huCXCR5 cells were pre-blocked with anti-human Fc for 15 min at 37°C, incubated with a pre-complexed huCXCL13/antibody mix for 2 h at 37°C, and subsequently stained with anti-human CXCR5 antibody for flow cytometric analysis. (A) Cell surface CXCR5 receptor expression. Geometric mean values were determined by FlowJo 7.6 software. (B) EC50 values were calculated from sigmoidal dose response curves (shown on the graph) with R2 values equal to 0.9 (MAb 5261) and 0.98 (MAb 5261-muIg). Data points represent an average of measurements obtained from 3 independent experiments.