Heterohybridomas between Epstein-Barr virus-transformed human B cells and murine myeloma P3X63Ag8.653 cells were found to produce sizable quantities of human monoclonal antibodies in nude mouse ascites. Mice injected intraperitoneally with two of such heterohybridomas yielded several milliliters of ascites fluid which contained nearly 100-fold higher anti-platelet activities than those in routine culture supernatants.
