Monoclonal antibody-induced murine hemolytic anemia

A panel of 11 IgG monoclonal antierythrocyte antibodies was generated by fusing spleen and bone marrow cells from unimmunized New Zealand black mice with the nonsecreting murine plasmacytoma cell line P3.X63.NS1. The monoclonal antibodies were detected by indirect hemagglutination of unaltered erythrocytes from several strains of mice. Seven of the antibodies cross-reacted with rat erythrocytes, but none of the antibodies agglutinated erythrocytes from any other species tested. Seven of the monoclonal antibodies were also capable of fixing rabbit complement. In vivo studies utilizing these 11 IgG-secreting hybridomas were performed in syngeneic BALB/c mice. Mice injected with nine of the hybridomas showed positive direct antiglobulin test results but did not become anemic. In contrast, hybridoma 114, secreting an IgG3 antibody, and hybridoma 245, secreting an IgG1 antibody, were both capable of mediating an acute, rapidly fatal hemolytic anemia. Intraperitoneal injection of hybridomas 114 and 245 resulted in positive direct and indirect antiglobulin test results, decreased hematocrit level, and reticulocytosis 3 to 6 days after cell injection. The mice survived a mean of 8 days, and death was associated with severe anemia and spontaneous erythrocyte agglutination. Autopsy studies revealed hepatosplenomegaly, small mesenteric tumor (hybridoma) mass, and no ascites. The liver and spleens were characterized histologically by erythrophagocytosis, extramedullary hematopoiesis, and hemosiderin deposition. Acute hemolytic anemia in BALB/c mice mediated by hybridomas 114 and 245 represents a new animal model that can be used to further define the mechanisms of immune hemolytic disease.