Affiliation:
1. Department of Laboratory Medicine and Pathology, University of Minnesota School of Medicine, Minneapolis 55455–0315.
Abstract
Abstract
The purpose of this study was to examine the expression and structure of CD22 in B cell precursor acute lymphoblastic leukemia (BCP-ALL), acute myeloid leukemia (AML), and T cell acute lymphoblastic leukemia (T-ALL). By using immunofluorescence microscopy and flow cytometry we observed that CD22 is expressed not only in the cytoplasm (as previously reported) but also on the cell surface of virtually all (15/16) BCP-ALL examined. CD22 that was biosynthetically labeled with 35S-cysteine and immunoprecipitated from the uncommon cytoplasmic CD22- positive/surface CD22-negative BCP-ALL cells was analyzed by single- dimension sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Our results indicated that the cytoplasmic form of CD22 comigrated with 125I/lactoperoxidase-labeled surface CD22. Therefore, cytoplasmic CD22 is probably a pool of fully processed glycoprotein. We also observed unusual cases of AML (approximately 20%) that expressed cytoplasmic CD22 based on immunofluorescent staining; however, biosynthetic labeling and immunoprecipitation revealed an apparently cross-reactive protein(s) of approximately 250 to 300 kd in AML cells. No T-ALL cell lines examined expressed either cytoplasmic or surface CD22. Thus, cytoplasmic and surface expression of bona fide CD22 appears restricted to B cells, which suggests that this molecule subserves a function unique to B cells.
Publisher
American Society of Hematology
Subject
Cell Biology,Hematology,Immunology,Biochemistry
Cited by
41 articles.
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