Complement Receptor-positive, Sheep Erythrocyte Receptor-negative Lymphoblasts in Childhood Acute Lymphocytic Leukemia

Lymphoblasts from 36 children with acute lymphocytic leukemia and two children with convoluted lymphoma were evaluated for expression of membrane receptors for sheep erythrocytes, complement, and the Fc portion of immunoglobulin G as well as for surface membrane immunoglobulin. Thirty patients had lymphoblasts that failed to express these membrane markers, four patients had sheep erythrocyte receptor-positive lymphoblasts, and a third group of four patients had lymphoblasts that displayed complement receptors only. The complement receptor-positive (CR⁺) lymphoblasts did not exhibit cyto-chemlcal, adherent, or phagocytic properties consistent with monocyte differentiation. The CR⁺ lymphoblasts formed rosettes with complement-bearing zymosan particles as well as complement-bearing immunoglobulin sensitized sheep erythrocytes. However, CR⁺ lymphoblasts from one patient were capable only of binding zymosan particles activated with mouse but not human serum. The CR⁺ lymphoblasts did not respond by [metfiyl-³H]thymidine incorporation to mitogens or allogenic cells in the mixed-lymphocyte reaction. Whereas the lymphoblasts from two of the CR⁺ patients stimulated lymphocytes from normal individuals to proliferate in a mixed-lymphocyte reaction the lymphoblasts from another CR⁺ patient were incapable of stimulating a proliferative response in the mixed-lymphocyte reaction. A distinctive clinical profile has not emerged. However, the finding that two of the four patients have relapsed within 1 year suggests that CR⁺ lymphoblasts may be indicative of an unfavorable prognosis.