title: CD2 identifies a monocyte subpopulation with immunoglobulin E-dependent, high-level expression of Fc epsilon RI.
abstract: BACKGROUND
  Fc epsilon RI expression by monocytes can affect monocyte function via multiple mechanisms, thereby potentially influencing the generation of allergic inflammation. Previous studies on the in vivo regulation of monocyte Fc epsilon RI expression by ambient IgE have yielded conflicting results.
  
  
  OBJECTIVE
  We hypothesized that monocyte Fc epsilon RI expression is limited to a specific monocyte subset, and that within that subset Fc epsilon RI surface expression is correlated to serum IgE.
  
  
  METHODS
  Study 1: Blood was obtained from non-allergic subjects (n=14) and subjects with allergic asthma (n=18), hypereosinophilic syndrome (n=2), hyper-IgE syndrome (n=6), and helminth infection (n=4). Study 2: Blood was obtained from allergic subjects in a clinical trial of omalizumab before and during study drug treatment. Monocyte surface Fc epsilon RI expression was measured using flow cytometry.
  
  
  RESULTS
  Fc epsilon RI expression was significantly greater in the CD2(high) vs. CD2(low) monocyte subsets (31% vs. 1.9% median Fc epsilon RI+, respectively). In asthmatic and non-atopic healthy control subjects, CD2(low) monocytes expressed little or undetectable Fc epsilon RI. In study 1, Fc epsilon RI expression was highly correlated to serum IgE in the CD2(high), but not in the CD2(low) monocyte subpopulation (R values of 0.67 and 0.41, respectively). In study 2, omalizumab, but not placebo, caused a significant and sustained decline in Fc epsilon RI expression within the CD2(high) monocyte subset.
  
  
  CONCLUSIONS
  CD2 defines a monocyte subset with high Fc epsilon RI expression, whose magnitude is highly correlated to serum IgE. As such, this new description of CD2(high) monocytes as Fc epsilon RI-bearing cells suggests that they may be potential targets of anti-IgE immunomodulatory therapies.
authors.affiliation: The Laboratory of Allergic Diseases, NIAID, National Institute of Health, Bethesda, MD 20892-1881, USA.
authors.forename: Y X
authors.initials: YX
authors.lastname: Cheng
authors.forename: B
authors.initials: B
authors.lastname: Foster
authors.forename: S M
authors.initials: SM
authors.lastname: Holland
authors.forename: A D
authors.initials: AD
authors.lastname: Klion
authors.forename: T B
authors.initials: TB
authors.lastname: Nutman
authors.forename: T B
authors.initials: TB
authors.lastname: Casale
authors.forename: D D
authors.initials: DD
authors.lastname: Metcalfe
authors.forename: C
authors.initials: C
authors.lastname: Prussin
mesh_terms: D000328:Adult; D031164:Ambrosia; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D001249:Asthma / Q000276:immunology; D018801:CD2 Antigens / Q000032:analysis*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology*; D016130:Immunophenotyping; D018950:Lipopolysaccharide Receptors / Q000032:analysis; D008297:Male; D009000:Monocytes / Q000276:immunology*; D000069444:Omalizumab; D017455:Receptors, IgE / Q000032:analysis*; D006255:Rhinitis, Allergic, Seasonal / Q000188:drug therapy / Q000276:immunology; D018709:Statistics, Nonparametric
chemical_list: D000893:Anti-Inflammatory Agents; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D018801:CD2 Antigens; D018950:Lipopolysaccharide Receptors; D017455:Receptors, IgE; D000069444:Omalizumab; D007073:Immunoglobulin E