Expression and structure of CD22 in acute leukemia.
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.
Boué
D R
DR
Department of Laboratory Medicine and Pathology, University of Minnesota School of Medicine, Minneapolis 55455-0315.
LeBien
T W
TW
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte / Q000096:biosynthesis*; D000951:Antigens, Neoplasm / Q000096:biosynthesis*; D000954:Antigens, Surface / Q000096:biosynthesis; D001402:B-Lymphocytes / Q000032:analysis; D015815:Cell Adhesion Molecules; D002462:Cell Membrane / Q000032:analysis; D003593:Cytoplasm / Q000032:analysis; D006801:Humans; D037102:Lectins; D007945:Leukemia, Lymphoid / Q000276:immunology*; D015470:Leukemia, Myeloid, Acute / Q000276:immunology*; D011499:Protein Processing, Post-Translational; D051918:Sialic Acid Binding Ig-like Lectin 2; D013601:T-Lymphocytes / Q000032:analysis
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; C497867:CD22 protein, human; D015815:Cell Adhesion Molecules; D037102:Lectins; D051918:Sialic Acid Binding Ig-like Lectin 2