Cell surface markers in acute lymphoblastic leukemia

During the last nine years, two important methodologies have been used to characterize the cell surfaces of normal lymphocytes and malignant lymphoblasts. Normal mature T-cells have a receptor for sheep erythrocyte (E+) while mature B-cells bear membrane-bound immunoglobulin molecules (sIg+). These two findings can be used to divide acute lymphoblastic leukemia of childhood into three major groups; B-cell leukemia (sIg+ E-), which is rare (approximately 2 percent) and has the poorest prognosis, T-cell leukemia (sIg-, E+) which is more common (10 percent) but also has a poor prognosis and null cell leukemia (sIg-, E-) which is the most common (85 percent) and has the best prognosis. By the use of additional immunological methods, subgroups within T-cell leukemia and null cell leukemia have also been proposed. One of the most valuable of these additional methods is the detection of surface antigens. Three of the more commonly detected antigens currently being evaluated are (1) common leukemia antigen (cALL), (2) a normal B Lymphocyte antigen the Ia antigen (Ia) which is not generally expressed on most T lymphocytes and (3) a normal T lymphocyte antigen (T) not expressed on B lymphocytes. Within null cell leukemia, the most commonly identified and probably the largest subgroup if Ia+, cALL+, T-, E-, sIg-. In another but smaller subgroup within null cell leukemia, the lymphoblasts contain cytoplasmic immunoglobulin but do not express surface immunoglobulins or E receptors. This subgroup is designated pre B-cell leukemia. Subgroups with T-cell leukemia have also been suggested. These include T+ E-, T+ E+, in which the rosettes are thermolabile and T+ E+, in which the rosettes are thermostable. Whether or not there are any prognostic differences in these three subgroups remains to be determined.