Antigen related to cell proliferation in malignant gliomas recognized by a human monoclonal antibody. A human monoclonal antibody (CLN-IgG) was produced from a human-human hybridoma derived from lymphocytes of a patient with cervical carcinoma. The reactivities of this antibody with various human glioma tissues and cultured glioma cells and the characterization of the antigen recognized by CLN-IgG on malignant glioma cells were analyzed and reported. CLN-IgG reacted with various human glioma cells and glioma tissues, especially glioblastoma, but did not react with normal brain tissues or fetal brain tissues. A large amount of antigen recognized by CLN-IgG was expressed on cell membranes of undifferentiated glioma cells and of glioma cells at the G2/M tumor growth phase in cycling cells. Antigen recognized by CLN-IgG was detected in only one of seven samples of cyst fluid, and was not detected in 27 serum samples or 18 samples of cerebrospinal fluid from glioma patients. CLN-IgG exhibited antibody-dependent cell cytotoxicity against U-25 1 MG glioma cells and primary cultured cells of glioblastomas and anaplastic astrocytomas. These data suggest that the antigen recognized by CLN-IgG might be related to cell proliferation in malignant gliomas. Thus, CLN-IgG might be useful for immunotherapy or immunoimaging of malignant gliomas. 