Donor Batf3 inhibits murine lung allograft rejection and airway fibrosis

Radiation-induced fibrosis: Mechanisms and therapeutic strategies from an immune microenvironment perspective

Radiation-induced fibrosis (RIF) is a severe chronic complication of radiotherapy (RT) manifested by excessive extracellular matrix (ECM) components deposition within the irradiated area. The lung, heart, skin, jaw, pelvic organs and so on may be affected by RIF, which hampers body functions and quality of life. There is accumulating evidence suggesting that the immune microenvironment may play a key regulatory role in RIF. This article discussed the synergetic or antagonistic effects of immune cells and mediators in regulating RIF's development. Several potential preventative and therapeutic strategies for RIF were proposed based on the immunological mechanisms to provide clinicians with improved cognition and clinical treatment guidance.

Surgeon-dependent histopathological variations in minor alloantigen-mismatched mouse lung transplantation

Background

The mouse orthotopic single lung transplant (LTx) model is an important scientific tool to explore LTx immunology. C57BL/10J (B10, H-2b) to C57BL/6J (B6, H-2b) minor alloantigen-mismatched LTx exhibits mild acute rejection and chronic fibrosis, mimicking human LTx, where acute rejection is dampened by immunosuppressants and chronic lung allograft dysfunction (CLAD) develops over time. However, we have observed variations in allograft histology across experiments, which were not explained by animal vendor or experimental conditions. The purpose of this study was to evaluate those variations objectively.

Methods

We performed a retrospective review of B10-to-B6 LTx performed in our laboratory 2012-2019. Only LTx without experimental interventions (eg, immunomodulatory agents or genetic modifications) examined at day 28 was eligible for this study. Mice from each surgeon were selected and divided into 3 groups to represent early, middle, and late timepoints in their mouse LTx experience (143 LTx from 5 surgeons). Histology from these LTx was graded in a randomized and blinded manner. Pathological variations and trajectories were graphed; logistic regression analyses were performed for statistical assessment.

Results

Distribution and trajectories of pathological outcomes were significantly different across surgeons. In multivariable logistic regression analyses, surgeon was associated with pathological outcomes whereas case number was not. Longer warm ischemia time was associated with more severe pleural fibrosis.

Conclusions

The B10 to B6 single LTx model can be a powerful tool to recapitulate CLAD-like histology. However, this is a challenging operation and surgeon-dependent variability in histopathological findings needs to be taken into account when designing experimental protocols.

The Immunopathology of Pulmonary Rejection after Murine Lung Transplantation

To improve outcomes following lung transplantation, it is essential to understand the immunological mechanisms that result in chronic graft failure. The associated clinical syndrome is termed chronic lung allograft dysfunction (CLAD), which is known to be induced by alloimmune-dependent (i.e., rejection) and alloimmune-independent factors (e.g., infections, reflux and environmental factors). We aimed to explore the alloimmune-related mechanism, i.e., pulmonary rejection. In this study, we use a murine orthotopic left lung transplant model using isografts and allografts (C57BL/6 or BALB/c as donors to C57BL/6 recipients), with daily immunosuppression (10 mg/kg cyclosporin A and 1.6 mg/kg methylprednisolone). Serial sacrifice was performed at days 1, 7 and 35 post-transplantation (n = 6 at each time point for each group). Left transplanted lungs were harvested, a single-cell suspension was made and absolute numbers of immune cells were quantified using multicolor flow cytometry. The rejection process followed the principles of a classic immune response, including innate but mainly adaptive immune cells. At day 7 following transplantation, the numbers of interstitial macrophages, monocytes, dendritic cells, NK cells, NKT cells, CD4+ T cells and CD8+ T and B cells were increased in allografts compared with isografts. Only dendritic cells and CD4+ T cells remained elevated at day 35 in allografts. Our study provides insights into the immunological mechanisms of true pulmonary rejection after murine lung transplantation. These results might be important in further research on diagnostic evaluation and treatment for CLAD.

Donor IL-17 receptor A regulates LPS-potentiated acute and chronic murine lung allograft rejection

Chronic lung allograft dysfunction (CLAD) is a major complication after lung transplantation that results from a complex interplay of innate inflammatory and alloimmune factors, culminating in parenchymal and/or obliterative airway fibrosis. Excessive IL-17A signaling and chronic inflammation have been recognized as key factors in these pathological processes. Herein, we developed a model of repeated airway inflammation in mouse minor alloantigen-mismatched single-lung transplantation. Repeated intratracheal LPS instillations augmented pulmonary IL-17A expression. LPS also increased acute rejection, airway epithelial damage, and obliterative airway fibrosis, similar to human explanted lung allografts with antecedent episodes of airway infection. We then investigated the role of donor and recipient IL-17 receptor A (IL-17RA) in this context. Donor IL-17RA deficiency significantly attenuated acute rejection and CLAD features, whereas recipient IL-17RA deficiency only slightly reduced airway obliteration in LPS allografts. IL-17RA immunofluorescence positive staining was greater in human CLAD lungs compared with control human lung specimens, with localization to fibroblasts and myofibroblasts, which was also seen in mouse LPS allografts. Taken together, repeated airway inflammation after lung transplantation caused local airway epithelial damage, with persistent elevation of IL-17A and IL-17RA expression and particular involvement of IL-17RA on donor structural cells in development of fibrosis.