Hematopoietic stem cell transplant-related airflow obstruction

Donor B-cell alloantibody deposition and germinal center formation are required for the development of murine chronic GVHD and bronchiolitis obliterans

Chronic GVHD (cGVHD) poses a significant risk for HSCT patients. Preclinical development of new therapeutic modalities has been hindered by models with pathologic findings that may not simulate the development of human cGVHD. Previously, we have demonstrated that cGVHD induced by allogeneic HSCT after a conditioning regimen of cyclophosphamide and total-body radiation results in pulmonary dysfunction and airway obliteration, which leads to bronchiolitis obliterans (BO), which is pathognomonic for cGVHD of the lung. We now report cGVHD manifestations in a wide spectrum of target organs, including those with mucosal surfaces. Fibrosis was demonstrated in the lung and liver and was associated with CD4(+) T cells and B220(+) B-cell infiltration and alloantibody deposition. Donor bone marrow obtained from mice incapable of secreting IgG alloantibody resulted in less BO and cGVHD. Robust germinal center reactions were present at the time of cGVHD disease initiation. Blockade of germinal center formation with a lymphotoxin-receptor-immunoglobulin fusion protein suppressed cGVHD and BO. We conclude that cGVHD is caused in part by alloantibody secretion, which is associated with fibrosis and cGVHD manifestations including BO, and that treatment with a lymphotoxin-β receptor-immunoglobulin fusion protein could be beneficial for cGVHD prevention and therapy.

Does high-resolution CT has diagnostic value in patients presenting with respiratory symptoms after hematopoietic stem cell transplantation?

BACKGROUND

Hematopoietic stem cell transplantation (SCT) can be complicated by a variety of live-threatening infectious and non-infectious pulmonary complications. The management of these complications is critically dependent on the most probable diagnosis, which is in part based on imaging work-up.

METHODS

Systematic review of the literature related to the diagnostic value of high-resolution computed tomography (HRCT) in patients who underwent SCT and developed respiratory symptoms.

RESULTS

Literature review did not reveal systematic cohort studies that included patients with respiratory symptoms post-SCT who underwent HRCT and had a well-defined outcome. Most studies selected participants based on their final diagnosis instead of the indication for diagnostic testing in practice. Nevertheless, several papers clearly indicated a potential role for HRCT when complications after SCT occur. A variety of articles described the role of certain HRCT findings in the diagnosis of specific infectious complications, but less data were available for non-infectious complications.

CONCLUSION

We believe more diagnostic studies are needed to determine the value of HRCT for a specific diagnosis in SCT-recipients who present with respiratory symptoms at the transplant clinic. Currently, radiologists should be cautious since HRCT interpretation in these patients is not unambiguous.

Lung function and late pulmonary complications among survivors of hematopoietic stem cell transplantation during childhood

Hematopoietic stem cell transplantation (HSCT) is used to treat an expanding array of malignant and non-malignant disorders. Pulmonary complications represent a significant source of morbidity and mortality in HSCT recipients. Young children, whose lungs are still developing and growing, may be especially susceptible to the insults of irradiation, drug toxicities, and recurrent infections associated with immunosuppression. Late pulmonary complications, those occurring more than three months after transplantation, are often noninfectious and present with nonspecific symptomatology. Pulmonary function testing (PFT) is a mainstay of monitoring pulmonary health in HSCT recipients. The pulmonologist should be familiar with common patterns seen on PFT in recipients of HSCT during childhood. In this review, we describe the findings in studies which have examined lung function over time in patients who underwent HSCT during childhood. We discuss patterns of PFT abnormalities, associated noninfectious syndromes and their clinical implications, as well as directions for future research.

Alloimmune lung injury induced by local innate immune activation through inhaled lipopolysaccharide

BACKGROUND

Alloimmune lung injury, characterized by perivascular lymphocytic inflammation, lymphocytic bronchiolitis (LB), and obliterative bronchiolitis (OB), causes substantial morbidity and mortality after lung transplantation and bone marrow transplantation (BMT), but little is known regarding its pathogenesis. We have developed and pursued the hypothesis that local activation of pulmonary innate immunity through toll-like receptor (TLR)-4 is critical to the development of posttransplant alloimmune lung injury.

METHODS

We developed a fully major histocompatibility complex-mismatched murine BMT model without systemic graft-versus-host disease, and challenged mice with aerosolized lipopolysaccharide (LPS), a prototypic TLR4 agonist, to determine the effect upon pulmonary alloimmune lung injury.

RESULTS

LPS-exposed allogeneic BMT recipient mice developed histological and biological features of LB and OB, which were not observed in non-LPS-exposed allogeneic controls or syngeneic LPS-exposed mice. LPS-induced lymphocytic lung inflammation was dependent upon intact TLR4 signaling in donor-derived hematopoietic cells but not recipient structural lung cells, demonstrating a distinct function for TLR4 on hematopoietic cells in mediating alloimmunity.

CONCLUSIONS

We demonstrate a critical role for localized, environmentally induced innate immune activation in promoting alloimmune lung injury. Local inhibition of TLR4 signaling in pulmonary resident hematopoietic cells represents a novel and potentially important therapeutic target to prevent posttransplant rejection.

Pulmonary dysfunction in pediatric hematopoietic stem cell transplant patients: non-infectious and long-term complications

Pulmonary complications are among the most frequently encountered sequelae of pediatric hematopoietic stem cell transplantation (HSCT). Non-infectious complications are becoming increasingly more common in this unique population. This review addresses the diagnosis and management of non-infectious manifestations of lung disease in pediatric HSCT patients and briefly discusses the long-term pulmonary function of childhood HSCT survivors.

Chronic GVHD and pretransplantation abnormalities in pulmonary function are the main determinants predicting worsening pulmonary function in long-term survivors after stem cell transplantation

Pulmonary function (PF) was studied in 69 consecutive patients with hematologic diseases, with a minimum 5-year (range, 5-13 years) follow-up after allogeneic stem cell transplantation from an HLA-matched sibling. Fifty-six patients (81%) received total body irradiation based myeloablative stem cell transplantation (MT) and 13 (19%) underwent nonmyeloablative stem cell transplantation (NST). Thirty-one patients (45%) developed a late decrease in PF from baseline, 25 with a restrictive and 6 with an obstructive pattern PF abnormality. Twelve patients (17%) were symptomatic, 8 with a severe restrictive PF defect, but none required supplemental oxygen. The incidence of developing a late PF abnormality was comparable in MT (24 of 56) and NST (5 of 13; P = .51). In multivariate analysis, chronic graft-versus-host disease (relative risk, 16) and pretransplantation diffusion capacity for carbon monoxide or forced expiratory volume in the first second <80% predicted were independently associated with a late decrease in PF from baseline (relative risk, 7). Our results indicate that late PF abnormality is common after MT and NST. Patients with a low pretransplantation diffusion capacity for carbon monoxide of or forced expiratory volume in the first second who developed chronic graft-versus-host disease were most severely affected. Longer follow-up is needed to determine whether PF will continue to decrease or reach a plateau and whether more patients with PF abnormality will eventually become symptomatic.