title: Mast cells in systemic mastocytosis have distinctly brighter CD45 expression by flow cytometry.
abstract: OBJECTIVE
  We sought to determine the significance of bright CD45 expression on mast cells in cases of systemic mastocytosis vs mast cells in bone marrows uninvolved by systemic mastocytosis and compare this CD45 expression with CD25 and CD2 expression on mast cells.
  
  
  METHODS
  Multiparameter flow cytometry was performed on 31 cases of systemic mastocytosis and 70 bone marrow cases that were not involved by systemic mastocytosis. Bright expression of CD45 was defined as more than 20% of CD117+ mast cells showing brighter CD45 expression than the average expression level of lymphocytes.
  
  
  RESULTS
  Mast cells with bright CD45 expression were seen in 26 systemic mastocytosis cases and three bone marrows uninvolved by systemic mastocytosis (sensitivity, 84%; specificity, 96%). CD25 alone had a greater sensitivity (100%) but lower specificity (93%) compared with bright CD45 for identifying abnormal mast cells, while CD2 alone had lower sensitivity but higher specificity. To reach a specificity of 100%, CD25 together with bright CD45 on mast cells was the optimal combination to detect cases of systemic mastocytosis.
  
  
  CONCLUSIONS
  A combination of bright CD45 and CD25 appears to specifically identify abnormal mast cells in cases of systemic mastocytosis. Further studies will be necessary to confirm these results.
authors.affiliation: From the Departments of Pathology and karen.chisholm@childrens.harvard.edu.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Chisholm
authors.affiliation: From the Departments of Pathology and.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Merker
authors.affiliation: Medicine, Stanford University School of Medicine, Stanford, CA, and.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Gotlib
authors.affiliation: From the Departments of Pathology and.
authors.forename: Gary
authors.initials: G
authors.lastname: Gitana
authors.affiliation: From the Departments of Pathology and.
authors.forename: Martina
authors.initials: M
authors.lastname: Lefterova
authors.affiliation: From the Departments of Pathology and.
authors.forename: James L
authors.initials: JL
authors.lastname: Zehnder
authors.affiliation: Department of Pathology, University of New Mexico School of Medicine, Albuquerque.
authors.forename: Tracy I
authors.initials: TI
authors.lastname: George
authors.affiliation: From the Departments of Pathology and.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Arber
authors.affiliation: From the Departments of Pathology and.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Ohgami
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001853:Bone Marrow / Q000276:immunology; D001854:Bone Marrow Cells / Q000378:metabolism / Q000473:pathology; D018801:CD2 Antigens / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D053645:Interleukin-2 Receptor alpha Subunit / Q000378:metabolism; D017493:Leukocyte Common Antigens / Q000378:metabolism*; D008297:Male; D008407:Mast Cells / Q000378:metabolism* / Q000473:pathology; D034721:Mastocytosis, Systemic / Q000378:metabolism* / Q000473:pathology*; D008875:Middle Aged; D019009:Proto-Oncogene Proteins c-kit / Q000276:immunology / Q000378:metabolism*; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D018801:CD2 Antigens; C508017:IL2RA protein, human; D053645:Interleukin-2 Receptor alpha Subunit; D019009:Proto-Oncogene Proteins c-kit; D017493:Leukocyte Common Antigens; C516769:PTPRC protein, human
keywords: Bone marrow; CD45; Flow cytometry; Systemic mastocytosis