E receptors on blasts from untreated acute lymphocytic leukemia (ALL): comparison of temperature dependence of E rosettes formed by normal and leukemic lymphoid cells.

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.