In vitro stimulation prior to fusion generates antigen-binding human-human hybridomas

Production of useful human monoclonal antibodies has been limited by the inability to reliably generate and isolate antigen-specific B cells by in vivo immunization. An in vitro culture system employing antigen and mitogen to stimulate lymphocytes derived from solid lymphoid organs has been developed. Human tonsilar or splenic lymphocytes were stimulated in vitro with antigen and mitogen in short term culture and then fused with either of two enzyme deficient human B cell lines. This approach appears to expand antigen-specific B cell clones prior to fusion resulting in the production of a significant number of antigen-binding human hybridoma antibodies. The system has been effective in the production of human monoclonal antibodies following stimulation with KLH-ARS, a soluble antigen, and intact group B streptococcus, a particulate antigen. Hybridomas have been produced by fusion with two distinct parental human B cell lines supporting the previously reported observation that human B lymphoblastoid cell lines representing different stages of B cell differentiation may be useful fusion partners. The utility of the in vitro stimulation system in producing human-human hybridomas secreting antibody directed against two distinct classes of antigens establishes this approach as a generally useful method for the production of human monoclonal antibodies.