Immunological Typing of Acute Lymphoblastic Leukaemia

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Abstract
The blasts of 37 adult and 126 childhood cases of acute lymphoblastic leukaemia (ALL) were characterized with a panel of xeno‐antisera and rosette tests. The Orthoclone® monoclonal antibodies (OKT series) were applied as well. Like other investigators, we were able to distinguish 4 major classes of ALL: T‐ALL, common‐ALL with the subclass pre‐B‐ALL, null‐ALL, and B‐ALL. We did not encounter a common‐ALL antigen‐positive T‐ALL subclass. In both adult and childhood ALL, all classes were present, and in about the same frequency as reported by others. In children, common‐ALL was the most frequent (66%); in adults, null‐ALL (38%). T‐ALL was seen both in adults and in children with about the same frequency (27 and 23%, respectively). We found pre‐B‐ALL only in children. Patients with B‐ALL comprised the smallest group in both adults and children (8 and 1.5%, respectively). The application of the OKT antibodies led to recognition of 3 major subclasses of T‐ALL: an immature, a common thymocyte and a mature thymocyte subclass. These antibodies were helpful in defining a better classification of null‐ALL.With regard to remission induction and prognosis in adult ALL, complete remissions were always obtained in T‐ALL, followed by 70% of complete remissions in common‐ALL. The worst prognosis was encountered in null‐ALL and B‐ALL, with 50 and 0% remission, respectively, and a shorter survival in null‐ALL of those patients who achieved complete remission. Thus, the high number of cases of null‐ALL in adults partly explains the generally much worse prognosis for adult ALL.