Mobilization of plasma cells in healthy individuals treated with granulocyte colony-stimulating factor for haematopoietic stem cell collection

In mice, the plasma cell (PC) niche in the bone marrow is close to the haematopoietic stem cell (HSC) niche. We investigated whether PCs can be mobilized into the peripheral blood (PB) in healthy donors receiving granulocyte colony-stimulating factor (G-CSF) for the induction of HSC mobilization into the PB. G-CSF increased the count of circulating PCs 6-fold, that of circulating B lymphocytes 4-fold and that of circulating HSCs 44-fold. Mobilized circulating PCs comprised CD138− (62·2%) and CD138+ (37·8%) PCs, the latter being more mature based on increased CD27, CD38 and cytoplasmic immunoglobulin expression. Mobilized PCs had a phenotype close to that of steady-state PB PCs or in vitro generated PCs, but they expressed L-selectin only weakly. Finally, a median value of 0·4 × 106/kg donor PCs – one-thirtieth of the overall PC count in a healthy adult – was grafted into patients, which could contribute to immune memory recovery.