In vitro development of human monoclonal antibody-secreting plasmacytomas

A polyclonal human lymphoblastoid cell line transformed in vitro with Epstein-Barr virus produced specific anti-Rhesus D antibody. It was repeatedly enriched by rosetting procedures and subsequently cloned. The cloning conditions employed a combination of mouse macrophage feeder layers, antimycoplasma agents, and low density passage. Formal evidence of monoclonality was obtained in one case which was of human IgG1 isotype and was secreted at the level of 15-20 micrograms/ml. All clones showed long-term stability in culture after 10 months of continuous passage. Both polyclonal and monoclonal cell lines possessed antigens characteristic of highly differentiated B cells, yet they also expressed Epstein-Barr virus nuclear antigen (EBNA). This study exemplifies a simple method for obtaining monoclonal antibody secreting plasmacytomas of human origin.