Generation and characterization of secreting and nonsecreting human × mouse heterohybridomas obtained by in vitro immunization of human peripheral blood lymphocytes

Among the immortalizing fusion partners usable in the development of human monoclonal antibodies, nonsecreting human-mouse heteromyelomas are the most interesting. In vitro immunization of human peripheral blood lymphocytes (pretreated with leucine-O-methyl ester) with an immunogen, hemocyanin, before fusion, is a good methodology for generating nonsecreting heterohybrids. Their biological features have been extensively studied with particular attention to the level of human DNA. These heterohybrids retained more than 10% human DNA in the whole genome. However, nonsecreting heteromyeloma SHMD₃₃ used as reference has 1% human DNA. There is no significant difference between the level of human DNA in the nonsecreting heteromyelomas and that of the secreting parent heterohybrid. The loss of human immunoglobulin production by the nonsecreting clones is not necessarily related to the diminution of human DNA. The presence of plasma cells containing human intracytoplasmic immunoglobulins and the lack of any antibody in the supernatant culture of nonsecreting clones show that the blockage of human antibody production could occur at the secretory stage.