title: Human B cells express a CD45 isoform that is similar to murine B220 and is downregulated with acquisition of the memory B-cell marker CD27.
abstract: BACKGROUND
  Differences between human and murine B cells exist at all stages of B-cell development, including the stage of memory B-cell formation. B cells in mice are identified with the pan-B-cell-specific CD45 isoform, B220. In initial studies in humans, it appeared that B220 expression did not include all B cells. This study was performed to expand on those preliminary findings.
  
  
  METHODS
  Multiparameter flow cytometric detection of B220 expression on B cells was combined with a variety of B-cell markers.
  
  
  RESULTS
  In contrast to mice, B220 was not a pan-B-cell marker in humans but was downregulated in the majority of B cells that acquired the human memory B-cell marker, CD27, whereas a minor memory B-cell subset remained B220(+), suggesting differences in differentiation.
  
  
  CONCLUSIONS
  The B220 isoform in humans is developmentally regulated in humans, tied to the acquisition of a memory phenotype, and as such can be used as a differentiation-specific CD45 isoform, akin to the use of CD45 isoforms to distinguish between naive and memory T-cell subsets. Patients with immunodeficiency disorders, associated with defective memory B-cell generation and absent or reduced CD27(+) B cells, showed a corresponding lack of B220 downregulation consistent with altered differentiation of B-cell subsets.
authors.affiliation: Department of Laboratory Medicine, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, Maryland, USA. bleesingjacobh@uams.edu
authors.forename: Jack J H
authors.initials: JJ
authors.lastname: Bleesing
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Fleisher
mesh_terms: D000328:Adult; D000361:Agammaglobulinemia / Q000276:immunology / Q000473:pathology; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D015415:Biomarkers; D018956:CD5 Antigens / Q000378:metabolism; D015536:Down-Regulation / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology*; D007536:Isomerism; D017493:Leukocyte Common Antigens / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D018956:CD5 Antigens; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7; D017493:Leukocyte Common Antigens