Immunological characterization of blast cells in patients with acute lymphoblastic leukemia. Evaluation of its clinical significance.

A panel of lymphocyte surface markers was used to identify blast cells from 111 patients with acute lymphoblastic leukemia (ALL). Three groups of patients were found. 1) 14 patients with B derived ALL. Only three patients had a common ALL; in the other cases the blastic proliferation was featured by Burkitt's tumor cells or supervened in patients affected with chronic lymphocytic leukemia (CLL). 2) The blast cells from 28% of the patients with common ALL had T cell properties. 3) The cells from the largest group of patients did not bear B or T cell markers but were featured by the presence of a leukemia-associated antigen revealed by a rabbit antiserum to CLL B cells. Studies with another antiserum to CLL B cells as well as with an antiserum to foetal thymocytes revealed also leukemia-associated antigens but these antigenic determinants were present on all acute leukemia cells which had been tested and were therefore of no help to classify various leukemias. A number of clinical and hematological findings were more frequent in the group of patients with T cell ALL: high white blood cell counts, tumoral disease, thymic enlargement, meningeal involvement, strong acid phosphatase activity in blast cells. However no difference in the survival curve is yet apparent at 30 months.