FDC-specific mAbs 8D6 and 4G10 inhibit L3055 cell but not HK cell proliferation in vitro. Irradiated HK cells were pretreated with medium (control) and mAbs 3C8, 8D6, and/or 4G10 (20 μg/mL) as indicated and were then cultured with L3055 cells. Viable L3055 cell numbers were obtained at the end of a 4-day culture, and the results are shown as mean of triplicate ± SD (▪). No viable cells were recovered from the culture with L3055 cells alone (dashed line). In a separate experiment, HK cells (4 × 10⁴ cells/well in 6-well plates) were cultured in the presence of indicated mAbs for 4 days before cell count (□). Data from 1 of 4 reproducible experiments is shown.