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CD Markers

CD22


Reviewers: Nat Pernick, M.D., PathologyOutlines.com, Inc. (see Reviewers page)
Revised: 22 December 2010, last major update December 2010
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.

General
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● Pan B cell marker helpful for diagnosis of hairy cell leukemia

Terminology
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● Also called B lymphocyte cell adhesion molecule (BL-CAM), Sialic acid binding immunoglobulin-like lectin/Siglec-2

Physiology
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● Inhibits B cell receptor signaling via alpha 2,6 sialic acid ligand binding activity; also binds CD45 and has adhesion properties of a lectin (J Exp Med 2002;195:1207)
● May localize B cells in lymphoid tissues
● Ligand is CD75

Clinical features
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● Shows variability in flow cytometry expression between specimens from same patient (Am J Clin Pathol 2002;117:615), may be due to delayed processing (Cytometry B Clin Cytom 2010 Sep 24 [Epub ahead of print])
● Leukemic cells from infants with newly diagnosed preB leukemia may express CD22 with exon 12 deletion (Proc Natl Acad Sci USA 2010;107:16852)
● Epratuzumab (anti-CD22 antibody) may have therapeutic value as part of radioimmunotherapy in non-Hodgkin's lymphoma (J Clin Oncol 2010;28:3709); is also being investigated as an immunotoxin

Uses for pathologists
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● Pan B cell marker; helpful for diagnosis of hairy cell leukemia
● Aberrant CD22 expression is useful to detect monoclonal B cells of CLL admixed with benign polyclonal B cells (Am J Clin Pathol 2005;123:826

Positive stains - normal
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● B cells (considered a pan B cell antigen), dendritic cells, basophils

Positive stains - disease
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● Hairy cell leukemia; also pre B ALL
● Blastic plasmacytoid dendritic cell neoplasm (Cytometry B Clin Cytom 2009;76:237)
● Staining of other B cell leukemias/lymphomas is variable (Am J Clin Pathol 2002;117:615)

Negative stains
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● Myeloblasts, plasma cells

Micro images
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Normal tonsil

Additional references
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MIM 107266

End of CD Markers > CD22


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