New antigenic determinant common to human thymus leukaemia-associated antigens and common acute lymphoblastic leukaemia antigen.

In the present paper we demonstrate that there is an antigenic determinant common to two different types of human leukaemia-associated antigens, i.e. human thymus leukaemia-associated (HTL) antigens and common acute lymphoblastic leukaemia (cALL) antigen. In addition, there are distinct antigenic determinants which are unique to the HTL antigens or to the cALL antigen. The new, common antigenic determinant will be useful as a new differentiation marker of human haematopoietic cells as well as a new leukaemia-associated marker. In the present study, we used several different anti-human leukaemia antisera which include those prepared by immunizing rabbits (Nos. 7549 and 7550) with purified HTL antigens. The antisera 7549 and 7550, without any absorption, showed strong specificity as well as strong antibody activity toward leukaemia cells. These are the first anti-human leukaemia antisera, except for the monoclonal hybridoma antibodies, that show good specificity for leukaemia cells without prior absorption.