Antisera against leukaemia-associated antigens on human lymphocytes

Antisera were raised in rabbits against leukaemic lymphosarcoma (LSL) cells which carried surface markers of both thymus-derived T lymphocytes (T cells) and bone marrow-derived B lymphocytes (B cells). After absorption with leucocytes, erythrocytes and serum proteins from normal individuals, the antisera demonstrated significant complement-dependent cytotoxicity against leukaemic cells from patients with acute lymphoblastic leukaemia (ALL) (9/11), LSL (7/9) and chronic lymphocytic leukaemia (CLL) (9/12), with an antibody titre of 1:64 or greater. The antisera did not react with: (a) blood lymphocytes from clinically healthy individuals (0/23), patients with ono-lymphoproliferative disorders (0/8) and normal umbilical cords (0/3), (b) normal lymphocytes stimulated by pokeweed mitogen (0/7), allogeneic lymphocytes (0/3), fetuin (0/1), purified protein derivative (PPD) (0/2), and candida antigen (0/1); (C) normal marrow cells (0/3), (D) normal thymocytes (0/2) and (E) leukaemic cells from patients with acute myeloblastic (AML) (0/10) and chronic granulocytic leukaemia (CGL) (0/3). However, the antisera did react with lymphoblastoid cells from continuous B-cell lines derived from an AML patient and from a non-leukaemic individual and, to a lesser extent, with lymphocytes from patients with infectious mononucleosis. The antisera also reacted with lymphocytes from chronically infected tonsils. Cytotoxicity of the antisera against lymphoblastoid and tonsillar cells was inhibited by ALL and CLL cell-lysates; and, conversely, cytotoxicity against ALL cells was inhibited by the lymphoblastoid cell extract. In contrast, a cell lysate or extract from normal inhibited by the lymphoblastoid cell extract. In contrast, a cell lysate or extract from normal lymphocytes did not inhibit cytotoxicity toward lymphoblastoid, tonsillar or ALL cells. Cytotoxicity of the antisera was neutralized by a goat anti-rabbit IgG (GAR IgG). These results suggest that the antisera contained antibodies reactive with antigens possibly common to neoplastic lymphocytes, tonsillar cells, lymphoblastoid cells and some lymphocytes from patients with infectious mononucleosis.