Monoclonal antibody to a nucleolar antigen of human B-lymphoblastoid cells

An anti-nucleolar monoclonal antibody reacting with human B-lymphoblastoid cells but not with normal peripheral blood lymphocytes has been isolated. The antibody recognized in Namalwa cells an antigen with molecular mass 41 kDa and pI 5.6, different from all previously described nucleolar antigens. Inhibition of rRNA transcription with Actinomycin D caused redistribution of the 41/5.6 antigen, but even at long term drug action it remains associated with the nucleolar remnants.