In the last decade there has been increasing awareness of the importance of thymus gland function in the reconstitution of host immunity following hematopoietic transplantation. A functional thymus contributes to foster T compartment reconstitution, with an increased diversity of T receptor rearrangement, and a more physiological distribution of the functional subpopulations. Palifermin, a keratinocyte growth factor (KGF) approved for reducing the incidence and severity of oral mucositis, has been proposed as a possible strategy for improving thymus function and immune reconstitution after hematopoietic transplantation. In vitro and animal models show palifermin to protect the thymus from chemo-/radiotherapy induced damage, increasing thymic production, accelerating immune reconstitution, improving response to vaccines, and reducing the incidence of graft-versus-host disease in animal models. To date, no studies have analyzed this possible application in humans. This study reports preliminary data on immune reconstitution in 50 autologous transplant recipients (30 treated with palifermin and 20 controls). The results suggest that palifermin at the doses and involving the regimens indicated for the prevention of oral mucositis has no effect upon thymus gland function in adult patients, and induces no changes in T immune recovery (either CD4 or CD8) or in the percentage of functional T subpopulations or T helper lymphocytes.