Cellular Binding and Internalization Assay for an Anti-FcγRIIB Antibody Using Human Liver Non-parenchymal Cells

A cellular assay for evaluating the binding and internalization of biologics using primary human liver sinusoidal endothelial cells (LSEC) is not readily available, since human LSEC generally lose their receptor expression and internalization activity during the purifying processes and cell culturing. Here, we propose a novel cell-based assay using human liver non-parenchymal cells (NPC) as an alternative method using LSEC. To identify the LSEC population, NPC were stained with CD31 and CD45, and analyzed by flow cytometry. The expression of Fc gamma receptor IIB (FcγRIIB), one of the LSEC markers was detected in the CD31-positive and the CD45-negative fractions. The concentration-dependent binding and internalization of the anti-FcγRIIB antibody was also quantified in the LSEC fraction in human NPC. Saturated binding and internalization curves were obtained for the anti-FcγRIIB antibody. In the case of the negative control antibody, however, binding and internalization were negligible. The findings reported here indicate that cell-based assays using fresh human liver NPC will be useful for evaluating the binding and internalization of biologics as well as for determining pharmacokinetic parameters.