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Chronic lung allograft rejection is associated with a progressive form of constrictive bronchiolitis that targets conducting airways while sparing larger airways as well as terminal bronchioles and the alveolar surface.

SUMMARYChronic rejection after organ transplantation is defined as a humoral-and cell-mediated immune response directed against the allograft. In lung transplantation, chronic rejection is nowadays clinically defined as a cause of chronic lung allograft dysfunction (CLAD), consisting of different clinical phenotypes including restrictive allograft syndrome (RAS) and bronchiolitis obliterans syndrome (BOS). However, the differential role of humoral and cellular immunity is not investigated up to now. Explant lungs of patients with end-stage BOS (n = 19) and RAS (n = 18) were assessed for the presence of lymphoid (B and T cells) and myeloid cells (dendritic cells, eosinophils, mast cells, neutrophils, and macrophages) and compared to nontransplant control lung biopsies (n = 21). All myeloid cells, with exception of dendritic cells, were increased in RAS versus control (neutrophils, eosinophils, and mast cells: all P < 0.05, macrophages: P < 0.001). Regarding lymphoid cells, B cells and cytotoxic T cells were increased remarkably in RAS versus control (P < 0.001) and in BOS versus control (P < 0.01). Interestingly, lymphoid follicles were restricted to RAS (P < 0.001 versus control and P < 0.05 versus BOS). Our data suggest an immunological diversity between BOS and RAS, with a more pronounced involvement of the B-cell response in RAS characterized by a structural organization of lymphoid follicles. This may impact future therapeutic approaches.

SummaryDespite a worldwide need to expand the lung donor pool, approximately 75% of lung offers are not accepted for transplantation. We investigated the impact of liberalizing lung donor acceptance criteria during the last decade on the number of effective transplants and early and late outcomes in our center. All 514 consecutive lung transplants (LTx) performed between Jan 2000 and Oct 2011 were included. Donors were classified as matching standard criteria (SCD; n = 159) or extended criteria (ECD; n = 272) in case they fulfilled at least one of the following criteria: age >55 years, PaO 2 /FiO 2 at PEEP 5 cmH 2 O < 300 mmHg at time of offer, presence of abnormalities on chest X-ray, smoking history, presence of aspiration, presence of chest trauma, or donation after circulatory death. Outcome parameters were primary graft dysfunction (PGD) grade at 0, 12, 24, and 48 h after LTx, time to extubation, stay in intensive care unit (ICU), early and late infection, acute rejection and bronchiolitis obliterans syndrome (BOS), and survival. Two hundred and seventy-two recipients (63.1%) received ECD lungs. PGD grade at T0 was similar between groups, while at T12 (<0.01), T24 (<0.01), and T48 (<0.05), PGD3 was observed more often in ECDs. ICU stay (P < 0.05) was longer in ECDs compared with SCDs. Time to extubation, respiratory infections, acute rejection, lymphocytic bronchiolitis, BOS, and survival were not different between groups. Accepting ECDs contributed in increasing the number of lung transplants performed in our center. Although this lung donor strategy has an impact on early postoperative outcome, liberalizing criteria did not influence long-term outcome after LTx.

Chronic lung allograft dysfunction (CLAD) remains a frequent and troublesome complication after lung transplantation. Apart from bronchiolitis obliterans syndrome (BOS), a restrictive phenotype of CLAD (rCLAD) has recently been recognized, which occurs in approximately 30% of CLAD patients. The main characteristics of rCLAD include a restrictive pulmonary function pattern with a persistent decline in lung function (FEV1, FVC and TLC), persistent parenchymal infiltrates and (sub)pleural thickening on chest CT scan, as well as pleuroparenchymal fibroelastosis and obliterative bronchiolitis on histopathologic examination. Once diagnosed, median survival is only 6 to 18 months compared with 3 to 5 years with BOS. In this perspective we review the historic evidence for rCLAD and describe the different diagnostic criteria and prognosis. Furthermore, we elaborate on the typical radiologic and histopathologic presentations of rCLAD and highlight risk factors and mechanisms. Last, we summarize some opportunities for further research including the urgent need for adequate therapy. In this perspective we not only assess the current knowledge, but also clarify the existing gaps in understanding this increasingly recognized complication after lung transplantation.

Chronic lung allograft dysfunction (CLAD) remains the major barrier to long-term success after lung transplantation. This report compares gross and microscopic features of lungs removed from patients receiving a redo-transplant as treatment for CLAD.Lungs donated by patients with either the bronchiolitis obliterans syndrome (BOS) or restrictive allograft syndrome (RAS) phenotype of CLAD and appropriate control lungs (eight per group) were airinflated, frozen solid and kept frozen while a multi-detector computed tomography (MDCT) was obtained. The lung was then cut into 2-cm thick transverse slices and sampled for micro-CT and histopathology.The MDCT showed reduced lung volume with increased lung weight and density in RAS versus BOS and control ( p<0.05). Although pre-terminal bronchioles were obstructed in both phenotypes, RAS lungs showed a reduction of pre-terminal bronchioles ( p<0.01). Micro-CT and matched histopathology showed that RAS was associated with reduced numbers of terminal bronchioles/lung compared to BOS and controls ( p<0.01), with expansion of the interstitial compartment and obliteration of the alveolar airspaces by fibrous connective tissue.RAS is associated with greater destruction of both pre-terminal and terminal bronchioles. Additionally, the interstitial compartments are expanded and alveolar airspaces are obliterated by accumulation of fibrous connective tissue. @ERSpublications Restrictive allograft syndrome is associated with greater destruction of both pre-terminal and terminal bronchioles

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There were major differences in cytokine and chemokine expression in our different study groups. Especially IL-6, but also IP-10/CXCL10, and VEGF may be interesting mediators in RAS.