T- and b-lymphocytes and lymphoblasts in untreated acute lymphocytic leukemia

This study demonstrates in the peripheral blood and bone marrow of patients with untreated acute lymphocytic leukemia (ALL) the coexistence of two main subpopulations of lymphoid cells: 1) small lymphoid cells which bear the same surface markers as normal lymphocytes; and 2) blasts which in the majority of the patients lack these markers. The proportions of cells bearing different cell-surface markers were studied in 14 children with ALL at time of diagnosis. Thymus-dependent (T) cells were identified by spontaneous formation of rosettes with sheep erythrocytes, and thymus-independent (B) cells by immunofluorescence of surface immunoglobulins. Using these criteria we demonstrated small lymphocytes with T- or B-markers in the peripheral blood or bone marrow of all patients assayed. In contrast, in 10 of 14 children the blasts had no detectable markers. However, in 2 patients more than half of bone marrow blasts had T-cell surface receptors, and in another 2 the proportion of blasts forming rosettes was 2% and 17%. The initial blast cell count in peripheral blood was greater than 105/mm3 in both children with the higher proportion of T-lymphoblasts. An additional initial clininal feature in one of them was the presence of a large anterior mediastinal mass, probably thymus. After successful induction of remission there was an increase in the proportion of normal T-lymphocytes in the bone marrow of 9 children assayed. The results from this study suggest that the presence of T-lymphoblasts, which may be of thymic origin, is correlated with a more advanced disease at time of diagnosis.