Cytotoxic activity of L19mTNFα and TN11mTNFα (A) Cytotoxic activity on L-M mouse fibroblasts, expressed as a percentage of viability compared with controls (mean ± SD), of different concentrations (picomolar) of mTNFα, TN11mTNFα, and L19mTNFα without and with an excess of scFv L19 in the culture medium (150 μg/mL). (B) Immunocytochemistry (see “Materials and methods”) on L-M mouse fibroblasts using L19mTNFα (i) and TN11mTNFα (iii). Although no staining was visible by using TN11mTNFα (iii), a strong reactivity was found by using L19mTNFα (i) that, as shown in Bii, was completely abolished by an excess of scFv L19. Original magnification, × 440.