α4 integrin levels on mobilized peripheral blood stem cells predict rapidity of engraftment in patients receiving autologous stem cell transplantation.

Rapidness of leukocyte engraftment in patients receiving peripheral blood stem cell transplantation is clinically important because the risk of fatal opportunistic infections increases with time to engraftment. Adhesion receptor molecules on hematopoietic stem cells (HSCs) have been shown to modulate homing and engraftment of HSCs. Therefore, we correlated expression levels of α4 (CD49d) and α6 (CD49f) integrins in the CD34(+) HSC compartment with time to engraftment. Leukapheresis products from 103 patients were retrospectively analyzed for CD34, CD38, CD3, CD49f, and CD49d surface molecules by multiparameter flow cytometry. High expression levels of α4 integrin, but not α6 integrin on CD34(+) cells, were associated with regular engraftment of leukocytes (days 8-19), whereas low surface expression correlated with delayed recovery (> 19 days; P < .0005). We show that α4 integrin expression levels on HSCs in leukapheresis products predict the engraftment capacity of mobilized peripheral blood stem cells in peripheral blood stem cell transplantation patients.