Membrane structure of leukaemic lymphoblasts: implications for classification, immune manipulation and analysis of the disease

Acute lymphoblastic leukaemia is the commonest malignant disease in childhood. Antigens and receptors found on the surface membrane of the leukaemic lymphoblast have suggested a new classification of leukaemia based on the pathway and stage of differentiation of the leukaemic cell. Recent information suggests that lymphoblastic leukaemia in adults may also be defined in terms of measurable differentiation stages of the normal lymphoid cell. Children with acute leukaemia recognize their own leukaemic cells as foreign. The major antigen recognized by patients on leukaemic lymphoblasts is a 70,000 dalton cell membrane glycoprotein (gp 70). Soluble complexes of gp 70–IgG anti-gp 70 can be detected in serum of patients with acute leukaemia at initial diagnosis. Both the titre and the avidity of anti-gp 70 antibody may determine the response to treatment and prognosis in patients. Recent data suggest that part of the leukaemic cell membrane gp 70 may be related to the envelope gp 70 found on cell-free RNA retrovirus-like particles released spontaneously by human leukaemic cells. Insertion of ‘virus’ gp 70 into the normal lymphocyte membrane may be responsible for the immunogenic properties of the leukaemic cell membrane.