Bone marrow transplantation (BMT) is an important therapeutic option for a variety of malignant and nonmalignant disorders. Unfortunately, BMT recipients are at increased risk of infection, and in particular, pulmonary complications occur frequently. Although the risk of infection is greatest during the neutropenic period immediately following transplant, patients are still vulnerable to pulmonary infections even after neutrophil engraftment. We evaluated the risk of infection in this postengraftment period by using a well-established mouse BMT model. Seven days after syngeneic BMT, B6D2F1 mice are no longer neutropenic, and by 3 wk, they demonstrate complete reconstitution of the peripheral blood. However, these mice remain more susceptible throughout 8 wk to infection after intratracheal administration of Pseudomonas aeruginosa; increased mortality in the P. aeruginosa-infected BMT mice correlates with increased bacterial burden in the lungs as well as increased systemic dissemination. This heightened susceptibility to infection was not secondary to a defect in inflammatory cell recruitment to the lung. The inability to clear P. aeruginosa in the lung correlated with reduced phagocytosis of the bacteria by alveolar macrophages (AMs), but not neutrophils, decreased production of TNF-α by AMs, and decreased levels of TNF-α and IFN-γ in the bronchoalveolar lavage fluid following infection. Expression of the β2 integrins CD11a and CD11c was reduced on AMs from BMT mice compared with wild-type mice. Thus, despite restoration of peripheral blood count, phagocytic defects in the AMs of BMT mice persist and may contribute to the increased risk of infection seen in the postengraftment period.

Idiopathic pneumonia syndrome (IPS) is a frequently fatal complication after allogeneic stem cell transplantation (allo-SCT) that responds poorly to standard immunosuppressive therapy. The pathophysiology of IPS involves the secretion of inflammatory cytokines including IFN-γ and TNF-α along with the recruitment of donor T cells to the lung. CXCR3 is a chemokine receptor that is expressed on activated Th1/Tc1 T cell subsets and the expression of its ligands CXCL9 (monokine induced by IFN-γ (Mig)) and CXCL10 (IFN-γ-inducible protein 10 (IP-10)) can be induced in a variety of cell types by IFN-γ alone or in combination with TNF-α. We used a lethally irradiated murine SCT model (B6 → bm1) to evaluate the role of CXCR3 receptor:ligand interactions in the development of IPS. We found that Mig and IP-10 protein levels were significantly elevated in the bronchoalveolar lavage fluid of allo-SCT recipients compared with syngeneic controls and correlated with the infiltration of IFN-γ-secreting CXCR3+ donor T cells into the lung. The in vivo neutralization of either Mig or IP-10 significantly reduced the severity of IPS compared with control-treated animals, and an additive effect was observed when both ligands were blocked simultaneously. Complementary experiments using CXCR3−/− mice as SCT donors also resulted in a significant decrease in IPS. These data demonstrate that interactions involving CXCR3 and its primary ligands Mig and IP-10 significantly contribute to donor T cell recruitment to the lung after allo-SCT. Therefore, approaches focusing on the abrogation of these interactions may prove successful in preventing or treating lung injury that occurs in this setting.

Idiopathic pneumonia syndrome (IPS) is a major complication after allogeneic bone marrow transplantation (allo-BMT) and involves the infiltration of donor leukocytes and the secretion of inflammatory cytokines. We hypothesized that leukocyte recruitment during IPS is dependent in part upon interactions between chemokine receptor 2 (CCR2) and its primary ligand monocyte chemoattractant protein-1 (MCP-1). To test this hypothesis, IPS was induced in a lethally irradiated parent 3

Idiopathic pneumonia syndrome (IPS) is a significant cause of mortality after allogeneic bone marrow transplantation (allo-BMT), and tumor necrosis factor-␣ (TNF-␣) is a significant effector molecule in this process. However, the relative contribution of donor-versus host-derived TNF-␣ to the development of IPS has not been elucidated. Using a lethally irradiated parent 3 F1 mouse IPS model, we showed that 5 weeks after transplantation allo-BMT recipients developed significant lung injury compared with syngeneic controls, which was associated with increased bronchoalveolar lavage (BAL) fluid levels of TNF-␣, elevated numbers of donorderived TNF-␣-secreting T cells, and increased pulmonary macrophage production of TNF-␣ to lipopolysaccharide (LPS) stimulation. Allo-BMT with TNF-␣ ؊/؊ donor cells resulted in significantly reduced IPS severity, whereas utilization of TNF-␣-deficient mice as BMT recipients had no effect on IPS. We next determined that TNF-␣ secretion from both donor accessory cells (monocytes/macrophages) and T cells significantly contributed to the development of IPS. Importantly, the absence of donor T-cell-derived TNF-␣ resulted in a significant decrease in inflammatory chemokine production in the lung and near complete abrogation of IPS.Collectively, these data demonstrate that donor TNF-␣ is critical to the development of IPS and reveal a heretofore unknown mechanism for T-cell-derived TNF-␣ in the evolution of this process.

IntroductionAllogeneic stem cell transplantation (allo-SCT) is an important therapy for a number of malignant and nonmalignant diseases. The broader application of allo-SCT is limited by several complications, including the development of graft-versus-host disease (GVHD) and pulmonary toxicity. Diffuse lung injury can occur in 25% to 55% of allo-SCT recipients. [1][2][3][4][5][6] In approximately 50% of patients, infectious organisms are not identified, and these cases have been defined as idiopathic pneumonia syndrome (IPS). IPS is associated with mortality rates of more than 70% despite the use of high-dose steroids, broad-spectrum antimicrobial agents, and aggressive supportive measures. 1,4 This form of lung injury is characterized by complex pathophysiology involving cytotoxicity from irradiation and chemotherapy, 7,8 the production of inflammatory cytokines, 9-14 and the recruitment of both donor T cells and accessory cells. 12,[15][16][17] The expression of several chemokines is also increased in the lung after allogeneic SCT, [18][19][20][21] and recent data from our group have shown mechanistic links between specific chemokine receptor-toligand interactions and the recruitment of donor T cells, monocytes, and macrophages to the lung during IPS. 19,21 Regulated on activation, normal T-cell-expressed and secreted (RANTES/ CCL5) is a member of the CC chemokine family of proteins that is strongly chemoattractant for activated T cells, monocytes, eosinophils, and basophils. 22,23 Increased RANTES expression has been shown in a number of experimental systems, including those modeling transplantation rejection, 24 sclerodermatous GVHD, 25 and acute lung injury after allo-SCT. [18][19][20] RANTES can be produced by several cell types including fibroblasts, 26 epithelial [27][28][29] and endothelial cells, 30,31 activated T cells, 32 and macrophages, 33 and its expression can be induced by proinflammatory cytokines including tumor necrosis factor ␣ (TNF␣), interleukin-1 ␤ (IL-1␤), and interferon ␥ (IFN␥). 20,[26][27][28][29]31 CCR1 and CCR5 are the primary receptors for RANTES. These receptors are expressed on a variety of cells including activated Th1/Tc1 lymphocytes, macrophages, and immature dendritic cells, but neither receptor binds exclusively to RANTES. 34 We used a well-established murine SCT model, wherein IPS develops following myeloablative conditioning and in the context of major and minor histocompatibility differences between donor and recipient, to study the role of RANTES of leukocyte infiltration into the lung. IPS in this system is dependent upon the infusion of allogeneic T cells, along with the pretransplant radiation dose, 35 and involves the recruitment of alloreactive CD4 ϩ and CD8 ϩ T cells to the lung. 19,20,35 Although the severity of IPS is exacerbated by the addition of cytoxan to total body irradiation (TBI) in a related SCT model, 16 the effects of "chemotherapy only" conditioning regimens on For personal use only. on June 19, 2019. by guest www.bloodjournal.org From the develop...

Idiopathic pneumonia syndrome (IPS) is a frequently fatal complication following allogeneic stem cell transplantation (allo-SCT). Experimental models have revealed that TNF-alpha contributes to pulmonary vascular endothelial cell (EC) apoptosis, and modulates the infiltration of donor leukocytes into the lung parenchyma. The inflammatory effects of TNF-alpha are mediated by signaling through the type I (TNFRI) or type II (TNFRII) TNF receptors. We investigated the relative contribution of TNFRI and TNFRII to leukocyte infiltration into the lung following allo-SCT by using established murine models. Wild-type (wt) B6 mice or B6 animals deficient in either TNFRI or TNFRII were lethally irradiated and received SCT from allogeneic (LP/J) or syngeneic (B6) donors. At week 5 following SCT, the severity of IPS was significantly reduced in TNFRII-/- recipients compared to wt controls, but no effect was observed in TNFRI-/- animals. Bronchoalveolar lavage fluid (BALF) levels of RANTES and pulmonary ICAM-1 expression in TNFRII-/- recipients were also reduced, and correlated with a reduction of CD8(+) cells in the lung. Pulmonary inflammation was also decreased in TNFRII-/- mice using an isolated MHC class I disparate model (bm1 --> B6), and in bm1 wt mice transplanted with B6 TNF-alpha-/- donor cells. Collectively, these data demonstrate a role for TNF-alpha signaling through TNFRII in leukocyte infiltration into the lung following allo-SCT, and suggest that disruption of the TNF-alpha:TNFRII pathway may be an effective tool to prevent or treat IPS.

Biology of Blood and Marrow Transplantation 10 (2004) 20-20. doi:10.1016/j.bbmt.2003.12.078Received by publisher: 0000-01-01Harvest Date: 2016-01-04 12:23:26DOI: 10.1016/j.bbmt.2003.12.078Page Range: 20-2

Biology of Blood and Marrow Transplantation 11 (2005) 46-47. doi:10.1016/j.bbmt.2004.12.137Received by publisher: 0000-01-01Harvest Date: 2016-01-04 12:23:26DOI: 10.1016/j.bbmt.2004.12.137Page Range: 46-4