Abstract
The binding and internalization of growth hormone (GH), B-cell growth factor-1linterleukin-4 (BSF-1/IL-4), and Thy-1.2, in the mouse splenic lymphocytes have been described using an electron microscopic immunocytochemical technique. B-cell and T-cell lines in culture are used for the specific binding of BSF-1/IL-4 and Thy-1.2 respectively. A myeloma cell line, X63/Ag 8.653, showed negative bindings for both BSF-1/IL-4 and Thy-1.2. GH binding is found on the surface and in the cytoplasm of most lymphocytes, but is not internalized by the myeloma cells. BSF-1/IL-4 bindings recognized by a monoclonal rat anti-BSF-1/IL-4 antibody (11B11) are found mainly on B-cells, whereas weak bindings are observed on T-cells. Thy-1.2 bindings are specific for T-cells. BSF-1/IL-4 and Thy-1.2 bindings immunolabelled at freezing temperature and reincubation at 37°C for 20min are internalized by B-and T-cells respectively. These results indicate that immunocytochemical technique is a sensitive and powerful tool for detection of specific antigens on the cell surface or in the cytoplasm of cells in the immune system. The internalization of GH, growth factors, and specific antigens presents a possible mechanism of the growth promoting functions in the immune system.
