ARG098 cytotoxicity to human chondrocytes. (A) ARG098 binding activity to human chondrocytes was assessed by flow cytometory. The white area is stained with human IgM and the black area is stained with ARG098. (B) RA synoviocytes pretreated with anti-Fas neutralizing antibody clone SM1/23. (C) Representative cell viability of human chondrocytes following ARG098 treatment (Experiment 1: from 0.1 to 1000 ng/mL, Experiment 2: from 1 to 100 μg/mL) versus untreated condition, as measured by the WST assay. Black circles and black triangles, ARG098; white circles and white triangles, human IgM. Each point represents mean ± SEM (n = 5).