Figure 3.

Binding of folate receptor α+ beads to B cells expressing MOv18 antibody. (A) Gating strategy for Sp2/0 cells (10⁵ in 100 µl FACS buffer) expressing MOv18 IgG, incubated with fluorescent LumAvidin 5.6 µm microspheres coated with FRα via PEG12-biotin. Single live cells binding to the beads were sorted into individual wells in a 96-well plate. (B) Agarose electrophoresis of the heavy and light chain variable regions of immunoglobulin sequences obtained from the Sp2/0 cells and amplified by PCR. (C) Flow cytometric evaluations of purified MOv18 antibody, produced in-house from single Sp2/0 cell Ig sequences, and expressed as a human/chimeric IgG1. MOv18 recognized FRα-overexpressing IGROV1 cancer cells but not FRα-negative MDA-MB-231 breast cancer cells. Dark gray histogram: unstained IGROV1 cells; light gray histogram: non-specific anti-NIP (monoclonal) antibody alone; Red histogram: MOv18 antibody cloned from a single B cell.