Adenosine deaminase
external side of plasma membrane
Surface adenosine deaminase. A novel B-cell marker in chronic lymphocytic leukemia.
Previous studies found that ADA is present on the surface of mononuclear blood cells from healthy patients. Because the expression of this surface antigen depends upon the cell type, the presence of ADA on the plasma membrane of cells from patients with malignant hematologic diseases was studied by flow cytometry. The highest percentage of expression was found in CLL, whereas the lowest was found in T-cell-derived malignancies. The enzyme expression in immortalized cell lines showed a similar pattern, with the highest expression (95% +/- 5%) in the SKW64 B-derived cell line, the lowest (15% +/- 5%) in Jurkat T-lymphoma derived cells, and the intermediate (32% +/- 8%) in K562 cells derived from a chronic myelogenous leukemia. Double labeling ADA/CD5 and ADA/CD19, as well as the correlation of ADA expression with the expression of other surface markers, indicate that surface ADA might be considered a novel marker for CLL.