CD22, a B lymphocyte-specific adhesion molecule that regulates antigen receptor signaling.
The development of B lymphocytes is a highly regulated process that depends in part on lineage-specific cell surface molecules. In addition, transmembrane signals generated through the B cell antigen receptor and other surface molecules regulate B cell responses to foreign antigens. Recent studies reveal CD22 to be a functionally significant receptor during these processes. CD22 is first expressed in the cytoplasm of pro-B and pre-B cells, and on the surface as B cells mature to become IgD+. CD22 is a member of the Ig superfamily that serves as an adhesion receptor for sialic acid-bearing ligands expressed on erythrocytes and all leukocyte classes. In addition to its potential role as a mediator of intercellular interactions, signal transduction through CD22 can activate B cells and modulate antigen receptor signaling in vitro. CD22 signaling is mediated via interactions with a number of kinases and phosphatases that bind the cytoplasmic domain through phosphorylated tyrosine residues located within consensus TAM and TIM motifs. The phenotype of CD22-deficient mice suggests that CD22 is primarily involved in the generation of mature B cells within the bone marrow, blood, and marginal zones of lymphoid tissues. Most notable in CD22-deficient mice is a significant diminution of surface Ig levels in these B cell subpopulations, which suggests that CD22 functions in vivo to adjust the signaling threshold of cell surface antigen receptors. A further understanding of CD22 function is required and may reveal roles for CD22 in disease susceptibility or the development of autoimmunity.
Tedder
T F
TF
Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710, USA. tedde003@mc.duke.edu
Tuscano
J
J
Sato
S
S
Kehrl
J H
JH
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001402:B-Lymphocytes / Q000276:immunology*; D002240:Carbohydrate Sequence; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002874:Chromosome Mapping; D006801:Humans; D037102:Lectins; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D051918:Sialic Acid Binding Ig-like Lectin 2; D015398:Signal Transduction
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497867:CD22 protein, human; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D037102:Lectins; D008024:Ligands; D011947:Receptors, Antigen, B-Cell; D051918:Sialic Acid Binding Ig-like Lectin 2