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Expression and structure of CD22 in acute leukemia
1Department of Laboratory Medicine and Pathology, University of Minnesota School of Medicine, Minneapolis 55455-0315.
Blood
|May 1, 1988
Summary
CD22, a protein crucial for B cells, is found on the surface and in the cytoplasm of B cell precursor acute lymphoblastic leukemia (BCP-ALL). This finding suggests CD22 plays a role unique to B cell development.
Area of Science:
- Immunology
- Cell Biology
- Hematology
Background:
- CD22 is a known B cell marker, typically found intracellularly.
- Previous studies suggested CD22 expression was limited to the cytoplasm.
Purpose of the Study:
- To investigate 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).
Main Methods:
- Immunofluorescence microscopy
- Flow cytometry
- Biosynthetic labeling with 35S-cysteine
- Immunoprecipitation
- SDS-PAGE
Main Results:
- CD22 is expressed on both the cell surface and in the cytoplasm of nearly all BCP-ALL samples (15/16).
- Cytoplasmic CD22 in BCP-ALL cells is a fully processed glycoprotein, similar to surface CD22.
- AML samples (approx. 20%) showed cytoplasmic expression, but it was a cross-reactive protein, not bona fide CD22.
- No CD22 expression (cytoplasmic or surface) was detected in T-ALL cell lines.
Conclusions:
- Bona fide CD22 expression (cytoplasmic and surface) is restricted to B cells.
- CD22 likely has a function unique to B cells.
- The presence of surface CD22 on BCP-ALL may have diagnostic or therapeutic implications.