ESTABLISHMENT AND CHARACTERIZATION OF PERMANENT MURINE HYBRIDOMAS SECRETING MONOCLONAL ANTI‐THY‐1 ANTIBODIES *

hybridomas secreting anti-Thy-1 antibodies were produced by fusing cells of the mouse myeloma line P3-NSI/1-Ag4-1 (NS-1) with spleen cells from AKR/J mice immunized with C3H/Di thymus cells and by subsequent growth in tissue culture and selection of the hybrid cells. Two permanent hybridomas, 1B5 and 1aG4/C5, secreting antibodies of IgG3 subclass were isolated by repeated cloning of cells by dilution and in soft agar. Growth of the hybrid cell colonies depended on the presence of feeder cells; spleen cells at 1-2 x 10(6)/ml were most effective, then thymus cells at 1-4 x 10(6)/ml and peritoneal cells at a concentration 1-2 orders of magnitude lower. The two hybridomas were grown in vitro or vivo and their products were further analysed. In tissue culture in serum-free medium under the optimum conditions the supernatant from hybridoma 1B5 contained 0.07 mg/ml of antibodies and that from hybridoma IaG4/C5 had 0.26 mg/ml of antibodies, whereas ascites 1B5 contained 3.6 mg/ml and ascites 1aG4/C5 4.4 mg/ml of antibodies. A very low electrophoretic mobility of both antibodies facilitated their isolation. The specificity of the antibodies was tested in the cytotoxicity assay in the presence of complement and by the binding of isotopically labelled antibodies to thymus cells from A/Ph mice and other Thy-1.2+ strains and A.Thy-1.1 and AKR/J mie. Antibodies of clone 1aG4/C5 were specific for Thy-1.2+ cells, whereas antibodies of clone 1B5 at higher concentrations also reacted with Thy-1.1+ cells from the thymus and lymph nodes. Both antibodies killed more than 95% thymus cells and 60-70% lymph node cells in the cytotoxicity assay. The specificity of antibodies for T lymphocytes was confirmed in the functional test in which the antibodies eliminated the response of spleen cells to Concanavalin A but did not affect the response to lipopolysaccharide in the presence of complement.