Expression and structure of CD22 in acute leukemia
DR Boue and TW LeBien
Department of Laboratory Medicine and Pathology, University of Minnesota
School of Medicine, Minneapolis 55455-0315.
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.
Volume 71,
Issue 5,
pp. 1480-1486,
05/01/1988
Copyright © 1988 by The American Society of Hematology
