White blood cells and the diagnosis of α-glucosidase deficiency

Abstract

Leukocytes were obtained from 14 healthy subjects, one patient with the infantile form, two patients with the adult variant of acid maltase deficiency, two patients with chronic myelocytic leukemia, two patients with acute myeloid leukemia, and two patients with chronic lymphotic leukemia. In addition, lymphocytes were prepared from three normal subjects, and five established lymphoid lines were used. Cells were extracted either with Triton 0, 2%, or with water followed by 0.2% Triton. α-Glucosidase activity was measured in water homogenates, water extracts after centrifugation, and Triton extracts, with or without antisera directed against acid maltase (EC 3.2.1.3) and renal maltase (EC 3.2.1.20). The percentage of acid and renal maltases was then calculated in each soluble fraction. Normal whole leukocytes (mostly granulocytes) contain both acid and “renal” maltases, whereas normal lymphocytes contain very little or no “renal maltase.” This isozyme is present in chronic myelocytic leukemia, but is absent in acute myeloid and chronic lymphocytic leukemia as well as in established lymphoid lines. Acid maltase is almost completely extracted with water, whereas renal maltase is extracted only with Triton. From the results, it appears that for the diagnosis of alpha glucosidase deficiency, cells should be extracted in water and centrifuged before determination. Lymphocytes, which are devoid of renal maltase, are a better diagnostic material than are granulocytes. Speculation: A specific isozyme of α-glucosidase, renal maltase, is found in the organism only in kidneys and white blood cells, whereas all other tested organs, including fibroblasts and cultured amniotic cells, do not possess this isozyme (unpublished results). Because its extractabUity differs from that of acid maltase, this property can be taken advantage of in activity determinations. The “renal” isozyme is still present in leukemic myelocytes, but not in myeloblasts. It seems, therefore, to be absent in young cells as well as in all cells of lymphocytic origin. © 1980 International Pediatric Research Foundation, Inc.