Effect of storage on lymphocyte surface markers in whole blood units

Pretransplant transfusions of stored donor-specific blood have been shown to improve renal allograft survival while reducing the frequency of lymphocytotoxic antibody production when compared with fresh blood. As part of studies to define the mechanism(s) of this phenomenon, we have monitored lymphocyte surface markers during storage of four units of whole blood. Both mononuclear cell preparations (obtained by density gradient centrifugation) and whole blood preparations were analyzed using monoclonal antibodies and a flow cytometer enabling lymphocytes to be distinguished from other white cells and nonviable cells. In both cell preparations, the percentage of viable lymphocytes expressing CD3 (all T cells), CD4 (T helper cells), CD8 (T suppressor cells,) HLA-class I (A,B,C), or HLA-DR antigens remained stable for at least 14 days, although median fluorescence intensity declined for the first three markers. After day 14, the number of viable lymphocytes recovered from a standard volume of whole blood was insufficient for further assessment of surface markers, even though the white cell count (determined by cell volume) remained near original levels. Thus the distribution of viable lymphocyte subpopulations defined by surface markers was stable for at least two weeks in stored blood; however, a nonspecific loss of lymphocyte viability began after 10 days of storage. These findings suggest that loss of cell viability, rather than loss of specific lymphocyte subpopulations, may be related to the mechanism by which pretransplant transfusion of stored blood improves renal allograft survival without inducing a high incidence of lymphocytotoxic antibody.