[Binding of K-18 on the surface of tumor cells--flowcytometrical analysis in vitro]

After K-18 was contacted with various kinds of tumor cell lines in vitro, the binding pattern was examined. K-18 bound on the surface of K-562 cells showed the maximum levels 1 hr later and maintained the binding activity for 24 hrs in the analysis by flowcytometry. K-18 also bound to HeLa S3, KB, RPMI8226, P815, YAC-1 and L1210 cells. Fluorescent intensity on K-562 cells was stronger with whole molecules of K-18 than with F(ab')2 conjugated with melphalan. Normal human IgG could bind more on the surface of K-562 cells than F(ab')2 of IgG. These results suggest that K-18 might bind on tumor cells via IgG Fc receptors on their surface.