We developed a modified monoclonal hybridoma technique that combines two conventional methods: a conventional immunosuppression method with cyclophosphamide treatment and an in vitro immunization method. This technique is advantageous over conventional methodologies because it requires a shorter period for immunization of mice and a smaller quantity of antigen, and gives rise to antibody-secreting hybridomas with higher efficiency. One monoclonal hybridoma line, designated as BG5, was established by this technique after activation of lymphocytes with muramyl dipeptide and with the immunogen obtained from human entorhinal cortex. Western blot analysis showed a relatively high expression of BG5 antigen in human entorhinal cortex. Our results suggest that this hybridoma technique may rapidly facilitate the acquisition of brain region-specific antibodies. We call this technique 'suppression immunization followed by in vitro stimulation procedure' (SOFISTIC).