Effects on proliferation of CD19+ B cells and macrophage migration inhibitory factor (MIF) concentration in vitro by milatuzumab. (A) Frequency of proliferated CD19+/CD3 -/CD14- B cells according to their carboxyfluorescein succinimidyl ester (CFSE) fluorescence intensity. CFSE-labeled peripheral blood mononuclear cells were cultured for 7 days with or without milatuzumab or intravenous immunoglobulin (IVIG) at 37°C in 5% CO2 and simultaneously stimulated with IL-2, IL-10, F(ab)2, and CpG (n = 6). Addition of milatuzumab as well as IVIG resulted in a modest, but significant, inhibition of the proliferation (Wilcoxon test). For each condition, a representative histogram is shown. (B) The concentration of the chemokine MIF as a potential ligand of CD74 was tested in cell culture supernatants (n = 7), as described above, and showed no significant differences between the conditions (Wilcoxon test). (C) Proportion of dead CD19+ B cells, identified as high positive staining with DAPI (n = 3). There was no substantial influence observed by either IVIG or milatuzumab (Wilcoxon test). *P ≤ 0.05. CpG, cytosine-phosphatidyl-guanosine; DAPI, 4,6 diamidino-2-phenylindole; F(ab)2, protein of two antigen-binding fragments; IL, interleukin; ns, not significant.