title: Identification of CD22 ligands on bone marrow sinusoidal endothelium implicated in CD22-dependent homing of recirculating B cells.
abstract: CD22 is a B cell-specific transmembrane protein known to function as a negative regulator of B cell signaling. It has also been implicated in cell adhesion through recognition of alpha2,6-linked sialic acids on glycans of target cells. Previous studies showed that CD22-deficient mice had a strongly reduced population of mature recirculating B cells in the bone marrow despite normal B cell development. Using a soluble recombinant form of the receptor (CD22-Fc), we demonstrate here that sialylated ligands for CD22 are expressed on sinusoidal endothelial cells of murine bone marrow but not on endothelial cells in other tissues examined. Injection of CD22-Fc revealed that the CD22 ligands in the bone marrow were accessible to the circulation. Treatment of mice with either CD22-Fc or affinity-purified anti-CD22 antibody led to an approximately 50% reduction in mature recirculating B cells in the bone marrow without affecting numbers in the spleen. Finally, consistent with the notion that CD22 is a homing receptor, we show that compared with wild-type mice, CD22-deficient animals have a lower number of immunoglobulin M-secreting plasma cells in the bone marrow.
authors.affiliation: Institute for Virology and Immunobiology, University of Würzburg, 97078 Würzburg, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Nitschke
authors.forename: H
authors.initials: H
authors.lastname: Floyd
authors.forename: D J
authors.initials: DJ
authors.lastname: Ferguson
authors.forename: P R
authors.initials: PR
authors.lastname: Crocker
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000378:metabolism*; D001402:B-Lymphocytes / Q000502:physiology*; D001853:Bone Marrow / Q000378:metabolism*; D016466:CHO Cells; D015815:Cell Adhesion Molecules; D002465:Cell Movement / Q000502:physiology*; D006224:Cricetinae; D004727:Endothelium / Q000378:metabolism; D037102:Lectins; D008024:Ligands; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019158:N-Acetylneuraminic Acid / Q000378:metabolism; D051918:Sialic Acid Binding Ig-like Lectin 2
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D037102:Lectins; D008024:Ligands; D051918:Sialic Acid Binding Ig-like Lectin 2; D019158:N-Acetylneuraminic Acid