Lymph node scanning in sheep with indium-111-labeled lymphocytes

Recirculating autologous lymphocytes of sheep were labeled in vitro with indium-111 and injected intravenously. Gamma camera pictures taken 24h later revealed detectable amounts of radioactivity in lymph nodes, spleen, liver and lungs. Single lymph nodes could be identified after the intravenous injection of as few as 108 lymphocytes labeled with as little as 50 μCi indium-111. The application of this procedure to human studies is discussed.