title: Longer storage of red blood cells is associated with increased in vitro erythrophagocytosis.
abstract: OBJECTIVE
  Refrigerated storage of red blood cells (RBCs) induces numerous changes that may target the cells for erythrophagocytosis following transfusion. The influence of storage upon the phagocytosis of unseparated and fractionated young and old stored RBCs was investigated using two in vitro quantitative phagocytosis assays.
  
  
  METHODS
  Leucocyte-depleted RBC units were sampled at day 1 or 42 of storage. Young and old RBCs were fractionated at day 1 by density centrifugation and stored in paediatric packs for up to 42 days. RBCs were labelled with the fluorescent dye PKH26 and incubated with the human monocytic cell line THP-1. Erythrophagocytosis was quantified by flow cytometry and plate fluorometric assays.
  
  
  RESULTS
  A higher proportion of THP-1 cells phagocytosed RBCs stored for 42 days compared with 1 day (41% and 24% respectively; P<0·0001). This was associated with an increased mean number of RBCs phagocytosed per THP-1 cell (5·2±0·6 and 3·3±0·2 respectively; P<0·002). Erythrophagocytosis of fractionated young and old RBCs increased with longer storage duration up to 28 days (P<0·05). However, no significant differences were observed between erythrophagocytosis of young and old RBCs.
  
  
  CONCLUSIONS
  The susceptibility of stored RBCs to erythrophagocytosis significantly increased with longer storage time of the RBC units. Storage duration of RBCs had a greater influence on in vitro erythrophagocytosis than the chronological age of the RBCs at donation.
authors.affiliation: Research and Development, Australian Red Cross Blood Service, Melbourne, Vic., Australia.
authors.forename: M F
authors.initials: MF
authors.lastname: Veale
authors.forename: G
authors.initials: G
authors.lastname: Healey
authors.forename: R L
authors.initials: RL
authors.lastname: Sparrow
mesh_terms: D000199:Actins / Q000037:antagonists & inhibitors; D001793:Blood Preservation / Q000009:adverse effects; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000276:immunology; D015638:Cytochalasin D / Q000737:chemistry; D004912:Erythrocytes / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000737:chemistry; D005470:Fluorometry; D006461:Hemolysis / Q000276:immunology; D006801:Humans; D009930:Organic Chemicals / Q000737:chemistry; D010587:Phagocytosis / Q000276:immunology*; D058105:Polymerization / Q000187:drug effects; D013997:Time Factors
chemical_list: D000199:Actins; D005456:Fluorescent Dyes; D009930:Organic Chemicals; C070080:PKH 26; D015638:Cytochalasin D
keywords: RBC senescence; erythrophagocytosis; stored RBCs