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The presence of receptors for sheep erythrocytes (E) and sufrace Ig on the bone marrow blasts was investigated in 29 children with untreated acute lymphocytic leukemia (ALL). In 6 of them more than 50% of the bone marrow blasts formed E rosettes, while in none of the 29 were surface Ig detected. The six children with rosette-forming blasts had WBS greater than 5 times 10-4/mm-3 at admission and 4 of them presented with thymic enlargement. E-positive ALL blasts and normal human thymocytes formed rosettes after incubation for 1 hr at 4 degrees C or 37 degrees C. In contrast, normal human peripheral T lymphocytes from blood, spleen, and pleural fluid also formed rosettes at 4 degrees C but these rosettes dissociated at 37 degrees C. In two patients with E-positive ALL, the disappearance from blood of cells forming rosettes at 37 degrees C during the 1st week of treatments paralleled the reduction in circulating blasts. Conversely, after 6 days of therapy almost one-half of the remaining cells formed rosettes at 4 degrees C and had the morphologic features of normal lymphocytes. We conclude that, in contrast to peripheral T cells, normal thymic cells and E-positive blasts share the property of forming E rosettes after 1-hr incubation at 37 degrees C. In patients with E-positive ALL this property may be used to evaluate drug effects upon leukemic and normal T lymphocytes.
Borella et al. (Wed,) studied this question.