Haematopoietic stem cells (HSCs) — from which all mature cells in the blood and immune system are derived — have enormous clinical potential for the reconstitution of immunity in patients with malignancies or diseases of the haematopoietic system. This month, two articles describe how different aspects of HSC transplantation could be improved to increase this therapeutic potential.
On page 878, Brian Sorrentino describes how our knowledge of the molecular pathways that control HSC self-renewal is being applied to the in vivo and in vitro amplification of HSCs. This should improve the rate of immune reconstitution and allow the use of HSCs from new sources such as umbilical-cord blood, which is currently limited by the small number of cells obtained. Functional immune reconstitution is also hampered by the slow recovery of the T-cell compartment, which increases the risk of opportunistic infections. Marcel van den Brink and colleagues (page 856) discuss clinical strategies that are being developed to speed up T-cell recovery after HSC transplantation. These include the co-transfer of committed lymphoid progenitors or ex vivo-generated T cells, strategies to increase thymic output, and the manipulation of hormones and growth factors that are involved in T-cell development and survival.
