title: Ultralarge von Willebrand factor multimers and normal ADAMTS13 activity in the umbilical cord blood.
abstract: BACKGROUND
  Recent studies demonstrate that deficiency of ADAMTS13, the metalloprotease that cleaves von Willebrand factor (VWF) in a shear-dependent manner, causes thrombotic thrombocytopenic purpura (TTP). Previously, ultralarge multimers of VWF were detected in the fetuses, the umbilical cords and the newborns. However, the significance of this finding is unknown.
  
  
  METHODS
  The activity of ADAMTS13 and the multimer pattern of VWF in the cord blood, as well as the VWF antigenic and ristocetin cofactor levels, were analyzed using previously published methods. The presence of ultralarge multimers was determined by densitometric analysis.
  
  
  RESULTS
  On the average, the level of VWF antigen and ristocetin cofactor activity are slightly increased in the newborns (mean+/-standard deviation, 1.66+/-0.76 and 1.45+/-0.64 U/ml, respectively). Ultralarge VWF multimers are detected in 11 of 17 umbilical cord plasma samples. However, the ADAMTS13 is normal (0.99+/-0.15 U/ml) in all but one sample in which it is mildly decreased (0.71 U/ml).
  
  
  CONCLUSIONS
  Since ADAMTS13 activity is normal, we speculate that the presence of ultralarge multimers in the umbilical cord blood may be due to the low levels of shear stress in the umbilical circulation. These results may have important implications for understanding the manifestation of ADAMTS13 deficiency during the neonatal period.
authors.affiliation: Division of Hematology, Montefiore Medical Center and Albert Einstein College of Medicine, 111 East 210th Street, Bronx, NY 10467, USA. htsai@montefiore.org
authors.forename: Han-Mou
authors.initials: HM
authors.lastname: Tsai
authors.forename: Ravindra
authors.initials: R
authors.lastname: Sarode
authors.forename: Katharine A
authors.initials: KA
authors.lastname: Downes
mesh_terms: D051722:ADAM Proteins; D000071120:ADAMTS13 Protein; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008666:Metalloendopeptidases / Q000097:blood* / Q000172:deficiency; D020836:Protein Structure, Quaternary; D011697:Purpura, Thrombotic Thrombocytopenic / Q000097:blood; D014841:von Willebrand Factor / Q000737:chemistry* / Q000378:metabolism
chemical_list: D014841:von Willebrand Factor; D051722:ADAM Proteins; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human