Production and Characterization of a Human Monoclonal Antibody Recognizing a New Antigen Expressed on Some Lymphoid Cells

A cell line secreting a human monoclonal antibody was established by Epstein‐Barr virus transforming B cells derived from an enlarged cervical lymph node excised from a patient bearing a carotid body tumor. The reactivity of the monoclonal antibody, designated as mNISP, was tested on various cells and cell lines. An antigen defined by the mNISP was expressed on some Burkitt's lymphoma cell lines and on a non‐T non‐B acute lymphoblastic leukemia cell line. Furthermore, this antigen was expressed on leukemic cells from 2 of 8 patients with chronic myelocytic leukemia, 2 of 10 patients with acute myeloblastic leukemia, one of 13 patients with acute lymphoblastic leukemia, and two patients with adult T cell leukemia, but it was not expressed on normal T, B and adherent (macrophage) cells. In addition, mNISP reacted with T cells obtained from human T‐cell leukemia virus type I carriers. We found that the antigen defined by mNISP was distinct from any previously reported antigen in terms of its pattern of cellular expression and molecular weight, suggesting that mNISP recognizes a new antigen expressed on some lymphoid cells.