Biodistribution study in F9 tumor-bearing mice. In all biodistribution experiments four mice were analyzed per group. Radioactivity content of tumor or organs is expressed as percentage of the injected dose per gram of tissue (%ID/g) ± standard error. (a) Comparison of intravenous and subcutaneous injection. Tumor bearing mice were injected intravenously or subcutaneously with 125I-labelled F8-IL10 and sacrificed 24 or 48 hours after injection. (b) Comparison of targeted and untargeted IL10. Mice were injected intravenously with 125I-labelled F8-IL10 or 125I-labelled HyHel10-IL10 (HyHel10 is an antibody specific to hen egg lysozyme and is not recognizing any murine antigen). They were sacrificed 24 hours after injection. (c) Residence time of F8-IL10 following subcutaneous administration. Mice were injected with 125I-labelled F8-IL10 and sacrificed 24, 48, 72, or 96 hours after injection.