title: A role in B cell activation for CD22 and the protein tyrosine phosphatase SHP.
abstract: CD22 is a membrane immunoglobulin (mIg)-associated protein of B cells. CD22 is tyrosine-phosphorylated when mIg is ligated. Tyrosine-phosphorylated CD22 binds and activates SHP, a protein tyrosine phosphatase known to negatively regulate signaling through mIg. Ligation of CD22 to prevent its coaggregation with mIg lowers the threshold at which mIg activates the B cell by a factor of 100. In secondary lymphoid organs, CD22 may be sequestered away from mIg through interactions with counterreceptors on T cells. Thus, CD22 is a molecular switch for SHP that may bias mIg signaling to anatomic sites rich in T cells.
authors.affiliation: Wellcome Trust Immunology Unit, Department of Medicine, University of Cambridge, School of Clinical Medicine, UK.
authors.forename: G M
authors.initials: GM
authors.lastname: Doody
authors.forename: L B
authors.initials: LB
authors.lastname: Justement
authors.forename: C C
authors.initials: CC
authors.lastname: Delibrias
authors.forename: R J
authors.initials: RJ
authors.lastname: Matthews
authors.forename: J
authors.initials: J
authors.lastname: Lin
authors.forename: M L
authors.initials: ML
authors.lastname: Thomas
authors.forename: D T
authors.initials: DT
authors.lastname: Fearon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000276:immunology* / Q000378:metabolism; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology* / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology*; D015815:Cell Adhesion Molecules; D002478:Cells, Cultured; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins; D037102:Lectins; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D051918:Sialic Acid Binding Ig-like Lectin 2; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497867:CD22 protein, human; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D007075:Immunoglobulin M; D047908:Intracellular Signaling Peptides and Proteins; D037102:Lectins; D011994:Recombinant Proteins; D051918:Sialic Acid Binding Ig-like Lectin 2; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse