title: Identification and characterization of the murine homologue of CD22, a B lymphocyte-restricted adhesion molecule.
abstract: The human B lymphocyte-specific Ag, CD22, is a cell adhesion molecule expressed on the surface during a narrow window of B cell development, coincident with surface IgD. A ligand for CD22 has recently been identified on human T cells as the low molecular mass isoform of the leukocyte common Ag, CD45RO. CD22 has been reported to function in the regulation of both T and B cell activation in vitro. In this study, we report the isolation and expression of a molecular cDNA clone encoding the murine homologue of CD22, mCD22. Within their predicted protein sequences, murine and human sequences overall have 62% identity, which includes 18 of 20 extracellular cysteines and six of six cytoplasmic tyrosines. BHK cells transfected with mCD22 cDNA specifically adhere to resting and activated T lymphocytes and in addition bound activated, but not resting, B cells. Five Th clones were analyzed for their ability to adhere to mCD22; two Th0 clones and one Th1 clone bound CD22+ BHK transfectants, but not all T cell clones bound CD22+ cells: another Th1 clone and a Th2 clone did not. mCD22+ BHK transfectants were also specifically bound by the B cell-specific mAb, NIM-R6, demonstrating that this mAb is specific for murine CD22. Human cell lines expressing the counter-receptors for human CD22 were also examined for adhesion to the murine CD22 homologue; the epitope responsible for B cell adhesion to CD22 is conserved, whereas the T cell epitope binding to CD22 is not. The cDNA and mAb to murine CD22 will be useful for defining the in vivo function of CD22.
authors.affiliation: Department of Microbiology, University of Washington, Seattle 98195.
authors.forename: R M
authors.initials: RM
authors.lastname: Torres
authors.forename: C L
authors.initials: CL
authors.lastname: Law
authors.forename: L
authors.initials: L
authors.lastname: Santos-Argumedo
authors.forename: P A
authors.initials: PA
authors.lastname: Kirkham
authors.forename: K
authors.initials: K
authors.lastname: Grabstein
authors.forename: R M
authors.initials: RM
authors.lastname: Parkhouse
authors.forename: E A
authors.initials: EA
authors.lastname: Clark
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000235:genetics* / Q000502:physiology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics* / Q000502:physiology; D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules; D002478:Cells, Cultured; D017124:Conserved Sequence; D006224:Cricetinae; D006801:Humans; D037102:Lectins; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D051918:Sialic Acid Binding Ig-like Lectin 2; D012799:Sialyltransferases / Q000032:analysis; D013601:T-Lymphocytes / Q000502:physiology; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497867:CD22 protein, human; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D037102:Lectins; D012333:RNA, Messenger; D051918:Sialic Acid Binding Ig-like Lectin 2; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase