Enhanced activation of B cells in a granulocyte colony-stimulating factor-mobilized peripheral blood stem cell graft

In a randomized study that compared human leucocyte antigen-identical allog eneic granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral bl ood stem cell (PBSC) versus bone marrow (BM) transplantation, the expressio n of activation markers, CD23, CD25 and CD45RO by B cells, was compared in blood before and after G-CSF mobilization and in PBSC versus BM grafts. The fractions of CD23(+) and CD25(+) B cells were higher in PBSC than in BM gr afts. Moreover, we observed a G-CSF-induced increase in B-cell fractions in blood as well as in PBSC grafts when compared with BM grafts. Such an enha nced B-cell activation could contribute to the accelerated kinetics of immu no-haematological reconstitution, the occurrence of acute haemolysis in the ABO minor incompatibility setting, as well as the increased incidence of c hronic graft-versus-host disease observed after PBSC transplantation.