Lymphoid antigens (LY) on leukaemic cell populations: Recognition by means of antilymphocytic globulins and clinical implications

Cells obtained from 120 cases of acute and chronic leukaemias (both non-lymphocytic, ANL, and lymphoid leukaemias, ALL) were reacted in an indirect immunofluorescence test with antilymphocytic globulins (ALG) directed against different lymphoid cell populations (spleen, lymph node, tonsil, thymus, thoracic duct, peripheral blood lymphocytes, chronic lymphatic leukaemias cells and cultured lymphoblasts). The aim of this study was to recognize lymphoid antigens expressed on both thymus and bone marrow derived lymphocytes, as well as on leukaemic cells. Our 4 years' experience can be summarized as follows: (1) unabsorbed ALGs strongly react with B, T cells, as well as with all leukaemic cells tested; (2) myeloid cross-reactivity can be overcome after proper absorptions with cells from AML or AMoL or CML or with neutrophils from healthy donors; (4) MY-absorbed ALG can still interact with B, T lymphocytes, CLL-cells, blasts from B, T, null ALL and cells from CML in lymphoid blastic crisis, but not with myeloid or monocytic cells; (5) four out of five undifferentiated leukaemias proved to be reactive to ALG, as well as four out of 31 AML. All ALG-positive cases (LY⁺ cases), irrespective of their cytochemical diagnosis, were treated with vincristine-prednisone, with good response rates. The biological and clinical significance of these results are discussed.