Donor T-cell production of RANTES significantly contributes to the development of idiopathic pneumonia syndrome after allogeneic stem cell transplantation.

Idiopathic pneumonia syndrome (IPS) is a major cause of mortality following allogeneic stem cell transplantation (allo-SCT). Clinical and experimental data support a role for conditioning-induced inflammation and alloreactive T-cell responses in IPS pathophysiology, but the mechanisms by which donor leukocytes are ultimately recruited to the lung are not fully understood. RANTES is a chemokine ligand that is up-regulated during inflammation and promotes the recruitment of T cells and macrophages to sites of tissue damage. Using a lethally irradiated murine SCT model (B6 --> B6D2F1), we evaluated the role of donor leukocyte-derived RANTES in the development of IPS. Pulmonary mRNA and protein levels of RANTES were significantly elevated in allo-SCT recipients compared to syngeneic controls and were associated with enhanced mRNA expression of CCR5 and CCR1 and with inflammatory cell infiltration into the lung. Allo-SCT with RANTES-/- donor cells significantly decreased IPS and improved survival. Combinations of allogeneic wild-type or RANTES-/- bone marrow with wild-type or RANTES-/- T cells demonstrated that the expression of RANTES by donor T cells was critical to the development of lung injury after SCT. These data reveal that donor T cells can help regulate leukocyte recruitment to the lung after allo-SCT and provide a possible mechanism through which inflammation engendered by SCT conditioning regimens is linked to allo-specific T-cell responses during the development of IPS.