Nucleolar antigen found in several human tumors but not in the nontumor tissues studied.

Rabbit antibodies to nucleoli isolated from HeLa cells produced bright nucleolar fluorescence in HeLa cells by the indirect immunofluorescence technique. After absorption with fetal bovine serum and placental nuclei, the IgG still produced bright nucleolar fluorescence in 12 human tumor cells including HeLa, HEp-2, cultures of prostate and mammary carcinomas, the Goldenberg GW-39 colon tumor, and biopsy specimens of prostatic, adrenal cortical, thyroid, and squamous cell carcinomas, a hairy cell leukemia of the spleen, a hepatic metastasis of an adenocarcinoma of the colon, and an osteogenic sarcoma. Bright nucleolar fluorescence was not produced in nine nontumor human cells including biopsy specimens of bone marrow, kidney, placenta, thyroid, liver, and prostate, peripheral blood buffy coat, and cultures of normal skin fibroblasts. Nucleolar fluorescence with the absorbed IgG was prevented in HeLa cells by pretreatment of the cells with acid, base, and proteases but not by pretreatment with nucleases; absorption of this IgG with extracts of HeLa nucleoli prevented the nucleolor fluorescence in HeLa and other human tumor cells.