Red blood cells with elevated cytoplasmic Ca(2+) are primarily taken up by splenic marginal zone macrophages and CD207+ dendritic cells.
The normal red blood cell (RBC) life span may be significantly reduced when RBCs are stored under blood bank conditions, resulting in a reduced 24-hour survival after transfusion. The damage of stored RBCs is probably multifactorial as stored RBCs share features of both senescence and suicidal RBC death (eryptosis). Since an increased intracellular Ca(2+) concentration ([Ca(2+) ]i ) is one key feature of eryptosis, we here investigated if stored human RBCs had increased [Ca(2+) ]i and the mechanisms behind uptake of such RBCs in a murine model.



The intracellular Ca(2+) content of RBCs was determined using the Ca(2+) probe Fluo-3 and flow cytometry. In vivo uptake of Ca(2+) ionophore-treated murine RBCs (Ca(2+) -RBCs) was investigated in recipient mice, using flow cytometry and immunohistochemical analysis.



A small fraction of human RBCs accumulated [Ca(2+) ]i during storage for up to 42 days under blood bank conditions. In a murine model, where fresh or Ca(2+) -RBCs were transfused, Ca(2+) -RBCs were mainly trapped by MARCO+ splenic marginal zone macrophages and CD11c+ CD207+ dendritic cells (DCs) within 1 hour after transfusion. In marked contrast, freshly transfused RBCs aging normally in circulation were cleared much slower and preferentially by F4/80+ red pulp macrophages. CD47 on the Ca(2+) -RBCs did not affect their clearance by splenic phagocytic cells.



A small fraction of RBCs accumulate [Ca(2+) ]i during storage, and in a murine model such RBCs are recognized by splenic macrophages and DCs in ways similar to what has been reported for nucleated apoptotic cells.
Department of Integrative Medical Biology and the, Umeå University, Umeå, Sweden.
Anders
A
Larsson
Department of Community Medicine and Rehabilitation, Section for Sports Medicine, Umeå University, Umeå, Sweden.
Andreas
A
Hult
Department of Integrative Medical Biology and the, Umeå University, Umeå, Sweden.
Anna
A
Nilsson
Department of Integrative Medical Biology and the, Umeå University, Umeå, Sweden.
Mattias
M
Olsson
Department of Integrative Medical Biology and the, Umeå University, Umeå, Sweden.
Per-Arne
PA
Oldenborg
D000818:Animals; D015703:Antigens, CD; D001793:Blood Preservation; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D003713:Dendritic Cells / Q000276:immunology*; D000072817:Eryptosis; D004912:Erythrocytes / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D037181:Lectins, C-Type; D008264:Macrophages / Q000276:immunology*; D037241:Mannose-Binding Lectins; D051379:Mice; D013154:Spleen / Q000166:cytology
D015703:Antigens, CD; C121916:CD207 protein, human; D037181:Lectins, C-Type; D037241:Mannose-Binding Lectins; D002118:Calcium