Establishment of monoclonal antibodies which possess the same characteristics as the naturally occurring thymocytotoxic autoantibodies (NTA).

Autoantibody-secreting hybrid cell lines were obtained by fusion of spleen cells from unimmunized (NZB X NZW) F1 mice with the HAT-sensitive mouse myeloma cell line SP2/0-Ag14. Eight hybridoma cell lines producing autoantibodies to mouse thymocytes were cloned and the resultant antibodies were partially characterized. All eight monoclonal antibodies lysed mouse thymocytes in the presence of rabbit complement. The anti-thymocyte cytotoxic antibody activities were absorbed with thymocytes, lymph node cells, unfractionated spleen cells, and splenic T cells; but not with bone marrow cells, splenic B cells, or homogenates of mouse kidney, liver, or striated muscle cells. In addition, the cytotoxic activities of culture supernatants from seven of the eight hybrid clones were absorbed with mouse brain tissue homogenates. Isotyping of the monoclonal antibodies revealed that five were IgM and three were IgG2a. Mouse thymocytes sensitized with each of the eight monoclonal antibodies in vitro became highly susceptible to phagocytosis by syngeneic macrophages. The monoclonal antithymocyte antibodies, thus, appear to be similar to the naturally occurring, (NZB X NZW) F1 thymocytotoxic autoantibodies (NTA) described by Shirai et al.