A novel human monoclonal antibody, TONO‐1, reactive with T‐lymphocytic leukemia cells

Mononuclear cells from the peripheral blood of patients with systemic lupus erythematosus (SLE) were transformed with the Epstein‐Barr virus (EBV) and the resultant polyclonal B‐lymphoblastoid cell lines were tested for antibody activity to membrane antigens of certain T‐cell lines. B lymphoblastoid cell lines secreting specific antibodies were fused with (mouse x human) heteromyeloma SHM‐D33 cells. Among the large number of hybridomas generated, one which produced a human monoclonal antibody (MAb) TONO‐I (1gM, λ) was selected. MAb TONO‐I proved to be reactive with 4 human T‐cell lines, HPB‐MLT, L‐MAT, MOLT‐3 and MOLT‐4F, but not with B‐leukemia, Burkitt's lymphoma, myelomonocytic leukemia, erythroleukemia or non‐hematopoietic malignant cell lines. MAb TONO‐I reacted positively with fresh leukemia cells from 2 of 7 patients with acute T‐lymphocytic leukemia, but no reaction was observed in non‐T‐cell leukemia cases. Normal lymphocytes, monocytes, granulocytes, red blood cells and platelets in the peripheral blood did not demonstrate remarkable binding. Neither thymocytes nor bone‐marrow cells from healthy volunteers were reactive. The antigens defined by MAb TONO‐I were polypeptides of 57 kDa and 68 kDa. Immunohistological studies revealed no staining of thymocytes in the thymus of a 6‐month‐old child, but showed epithelial reticular cells and Hassall's corpuscles to stain positively. These results suggest that MAb TONO‐I is directed to T‐leukemic cells and some components of thymus tissue. © 1995 Wiley‐Liss Inc.