title: Quantitative analysis of Howell-Jolly bodies in children with sickle cell disease.
abstract: OBJECTIVE
  Although functional asplenia in sickle cell disease (SCD) begins early in life and has important clinical consequences, quantitative measurement of splenic function is not readily available. A novel high-throughput flow cytometric method for quantitating Howell-Jolly bodies (HJB) has been developed which isolates HJB-containing CD71(+) and CD71(-) erythrocytes. Analysis of these cell populations allows quantitative measurement of splenic filtrative function and possible chromosomal damage.
  
  
  METHODS
  Blood specimens from 147 children with SCD were analyzed using a high-throughput flow cytometric method. Enumeration of the following populations was accomplished: 1) CD71(+) reticulocytes among total erythrocytes, identifying the youngest erythroid cell population; 2) HJB-containing CD71(+) reticulocytes, which isolate young erythrocytes containing micronuclei as an index of cytogenetic damage; and 3) HJB-containing CD71(-) erythrocytes, identifying older erythrocytes containing micronuclei, indirectly measuring splenic function.
  
  
  RESULTS
  Children with HbSC (n = 24) had slightly elevated HJB frequencies, while children with HbSS (n = 125) had highly elevated frequencies within CD71(+) cells (0.44% +/- 0.40%, normal 0.12% +/- 0.06%, p < 0.001) and CD71(-) cells (2493 +/- 2303 per million RBC, normal 20 +/- 11, p < 0.001). Using a multiple regression model, the frequency of HbSS CD71(+) reticulocytes containing HJB was significantly influenced by hydroxyurea use (p < 0.0001), age (p = 0.0288), and splenectomy (p = 0.0498). Similarly, mature CD71(-) erythrocytes containing HJB were positively correlated with hydroxyurea (p = 0.0001), age (p < 0.0001), and splenectomy (p = 0.0104).
  
  
  CONCLUSIONS
  HJB quantitation by flow cytometry is a novel assay for measuring splenic function and may be valuable for investigating the efficacy and safety of therapeutic options for children with SCD.
authors.affiliation: Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. virginia.harrod@stjude.org
authors.forename: Virginia L
authors.initials: VL
authors.lastname: Harrod
authors.forename: Thad A
authors.initials: TA
authors.lastname: Howard
authors.forename: Sherri A
authors.initials: SA
authors.lastname: Zimmerman
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Dertinger
authors.forename: Russell E
authors.initials: RE
authors.lastname: Ware
mesh_terms: D000293:Adolescent; D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood* / Q000235:genetics / Q000378:metabolism; D015703:Antigens, CD / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004908:Erythrocyte Inclusions / Q000378:metabolism / Q000473:pathology*; D004912:Erythrocytes / Q000378:metabolism / Q000473:pathology; D005260:Female; D005434:Flow Cytometry / Q000379:methods*; D005838:Genotype; D006451:Hemoglobin, Sickle / Q000032:analysis; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D015162:Micronucleus Tests; D011990:Receptors, Transferrin / Q000378:metabolism; D015203:Reproducibility of Results; D012156:Reticulocytes / Q000378:metabolism / Q000473:pathology; D013156:Splenectomy
chemical_list: D015703:Antigens, CD; C068126:CD71 antigen; D006451:Hemoglobin, Sickle; D011990:Receptors, Transferrin