Acrylic microspheres in vivo. X. Elimination of circulating cells by active targeting using specific monoclonal...

The elimination from the blood of 51Cr-labelled mouse erythrocytes modified with trinitrophenyl (TNP) groups was followed in mice. After 24 hours, when a stable concentration of the labelled erythrocytes has been attained, monoclonal anti-TNP-antibodies were given intravenously, either in free, soluble form, or bound to microparticles containing immobilized protein A. The anti-TNP-antibodies induced a rapid elimination of the TNP- and 51Cr-labelled erythrocytes. Over the 8-hours time period studied, the elimination rate was significantly faster when the antibodies were administered bound to the particles. After the elimination of the target cells, the radioactivity was found in the liver, spleen and bone marrow. These results and relevant control experiments indicate that a solid carrier 1. can be directed to a specific target cell with a specific antibody and 2. can induce a rapid elimination of the target cell from the circulation.