A role for TNF receptor type II in leukocyte infiltration into the lung during experimental idiopathic pneumonia syndrome.

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.

The absence of donor-derived IL-13 exacerbates the severity of acute graft-versus-host disease following allogeneic bone marrow transplantation.

Acute graft versus host disease (aGVHD) after allogeneic bone marrow transplantation (allo-BMT) predominantly involves a Th1-type cytokine response. Interestingly, the Th2-cytokine, Interleukin-13 (IL-13), produced by alloreactive donor T cells in vitro was recently shown to correlate with clinical aGVHD severity. Using an established mouse model, we show that the systemic cytokine milieu following allo-BMT with IL-13-/- donors is characterized by decreases in serum Th2 cytokines and an increase in serum TNFalpha, and ultimately correlates with higher aGVHD mortality compared to allogeneic controls. In vitro studies further demonstrate that both exogenous and T cell-derived IL-13 can regulate TNFalpha production by macrophages following lipopolysaccharide stimulation. Thus, donor-derived IL-13 may have a role in modulating inflammatory cytokine release that is associated with aGVHD.

CCR1/CCL5 (RANTES) receptor-ligand interactions modulate allogeneic T-cell responses and graft-versus-host disease following stem-cell transplantation.

Acute graft-versus-host disease (GVHD) and leukemic relapse are serious complications of allogeneic stem-cell transplantation (SCT). Recruitment of activated T cells to host target tissues or sites of leukemic infiltration (graft-versus-leukemia [GVL]) is likely mediated by chemokine receptor-ligand interactions. We examined the contribution of donor cell CCR1 expression to the development of GVHD and GVL using a well-established murine SCT model (B6 --> B6D2F1) and CCR1-deficient mice (CCR1(-/-)). Allo-SCT with CCR1(-/-) donor cells significantly reduced systemic and target organ GVHD severity, and CCR1 expression on both T cells and accessory cells contributed to GVHD mortality. Significant GVL activity was preserved following CCR1(-/-) SCT, but the survival advantage diminished with increasing tumor burden. We then explored the effects of CCR1 expression on allo-specific T-cell responses. Although cytolytic effector function was maintained on a per-cell basis, T-cell proliferation and IFNgamma secretion were significantly reduced both in vivo and in vitro. T-cell function was partially dependent on interactions between CCR1 and CCL5. Collectively, these data demonstrate that CCR1 expression on donor cells contributes to the development of both GVHD and GVL, and suggest that CCR1/CCL5 receptor-ligand interactions modulate allo-specific T-cell responses occurring in this context.

Donor CD4+ T-cell production of tumor necrosis factor alpha significantly contributes to the early proinflammatory events of graft-versus-host disease.

OBJECTIVE: Tumor necrosis factor alpha (TNFalpha) is an old foe in allogeneic bone marrow transplantation (allo-BMT) promoting acute graft-versus-host disease (aGVHD). We investigated to what extent donor T cells contribute to TNFalpha production. METHODS: Lethally irradiated B6D2F1 mice were transplanted with bone marrow (BM) and T cells from syngeneic B6D2F1 or allogeneic B6 donors and assessed for cytokine production, aGVHD, and survival. RESULTS: Analysis of serum TNFalpha kinetics in recipients of allogeneic B6 wild-type BM and wild-type T cells revealed that TNFalpha levels peaked around day 7 after allo-BMT, whereas TNFalpha was undetectable in syngeneic controls. TNFalpha was produced by both host and donor cells. Further exploration showed that specifically donor CD4(+) but not CD8(+) T cells were the primary donor cell source of TNFalpha at this early time point; numbers of TNFalpha expressing splenic CD4(+) T cells were higher than CD8(+) T cells 7 days after allo-BMT, and maximal serum TNFalpha levels were detected following allo-BMT with only CD4(+) T cells compared to levels found in allogeneic recipients of only wild-type CD8(+) or to only CD4(+) TNFalpha(-/-) T cells. Concurrent with increased TNFalpha levels, early clinical aGVHD and mortality were more severe following allo-BMT with either wild-type CD4(+) and CD8(+) or CD4(+) T cells only. CONCLUSION: Our data demonstrate that in addition to residual host cells donor CD4(+) T cells significantly contribute to the proinflammatory cytokine milieu engendered early after allo-BMT through the production of TNFalpha. These findings support strategies focusing on TNFalpha neutralization as primary treatment for aGVHD.

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.

Blockade of CXCR3 receptor:ligand interactions reduces leukocyte recruitment to the lung and the severity of experimental idiopathic pneumonia syndrome.

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-gamma and TNF-alpha 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-gamma (Mig)) and CXCL10 (IFN-gamma-inducible protein 10 (IP-10)) can be induced in a variety of cell types by IFN-gamma alone or in combination with TNF-alpha. 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-gamma-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.

Donor-derived TNF-alpha regulates pulmonary chemokine expression and the development of idiopathic pneumonia syndrome after allogeneic bone marrow transplantation.

Idiopathic pneumonia syndrome (IPS) is a significant cause of mortality after allogeneic bone marrow transplantation (allo-BMT), and tumor necrosis factor-alpha (TNF-alpha) is a significant effector molecule in this process. However, the relative contribution of donor-versus host-derived TNF-alpha to the development of IPS has not been elucidated. Using a lethally irradiated parent --> 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-alpha, elevated numbers of donor-derived TNF-alpha-secreting T cells, and increased pulmonary macrophage production of TNF-alpha to lipopolysaccharide (LPS) stimulation. Allo-BMT with TNF-alpha(-/-) donor cells resulted in significantly reduced IPS severity, whereas utilization of TNF-alpha-deficient mice as BMT recipients had no effect on IPS. We next determined that TNF-alpha 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-alpha 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-alpha is critical to the development of IPS and reveal a heretofore unknown mechanism for T-cell-derived TNF-alpha in the evolution of this process.

A critical role for CCR2/MCP-1 interactions in the development of idiopathic pneumonia syndrome after allogeneic bone marrow transplantation.

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 --> F1 mouse BMT model. Compared with syngeneic controls, pulmonary expression of MCP-1 and CCR2 mRNA was significantly increased after allo-BMT. Transplantation of CCR2-deficient (CCR2-/-) donor cells resulted in a significant reduction in IPS severity compared with transplantation of wild-type (CCR2+/+) cells and in reduced bronchoalveolar lavage (BAL) fluid cellularity and BAL fluid levels of tumor necrosis factor-alpha (TNF-alpha) and soluble p55 TNF receptor (sTNFRI). In addition, neutralization of MCP-1 resulted in significantly decreased lung injury compared with control-treated allogeneic recipients. Experimental data correlated with preliminary clinical findings; patients with IPS have elevated levels of MCP-1 in the BAL fluid at the time of diagnosis. Collectively, these data demonstrate that CCR2/MCP-1 interactions significantly contribute to the development of experimental IPS and suggest that interventions blocking these receptor-ligand interactions may represent novel strategies to prevent or treat this lethal complication after allo-BMT.

Defective phagocytosis and clearance of Pseudomonas aeruginosa in the lung following bone marrow transplantation.

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, B6D2F(1) 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-alpha by AMs, and decreased levels of TNF-alpha and IFN-gamma in the bronchoalveolar lavage fluid following infection. Expression of the beta(2) 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.