Dextran T fractions substituted with cibacron blue F3G-A as carriers for mouse interferon

Commercial dextran T fractions covering the molecular weight (Mt) range 10,000-2,000,000 were substituted with a covalently linked chromophore: Cibacron blue F3G-A. Mouse interferon (IF) was found to bind firmly to the blue dextran (BD) fractions. Fractions of high Mt (BD 2000 and BD 500) associated with IF are precipitated from the solution by polyethylene glycol (PEG). Fractions of lower Mt (BD 70, BD 40 and BD 10) associated with IF are only partially, if at all, precipitated by PEG. However, when BD-IF complexes of various Mt were analyzed by chromatography on Sephadex G-150, IF activity migrates together with BD and not at the distance characteristic of native IF. These data suggested that IF is bound to various BD fractions. BD-IF complexes of various Mt have almost the same antiviral and anticellular activities as native IF. BD-IF complexes are neutralized to a greater extent by antibody than native IF. Clearance of BD 70-IF complex from the mouse peritoneal cavity is slightly slower than native IF. However, the i.v. clearance of both forms of IF is almost the same.