Humoral immune responses mediate the development of a restrictive phenotype of chronic lung allograft dysfunction
Keizo Misumi, David S. Wheeler, Yoshiro Aoki, Michael P. Combs, Russell R. Braeuer, Ryuji Higashikubo, Wenjun Li, Daniel Kreisel, Ragini Vittal, Jeffrey Myers, Amir Lagstein, Natalie M. Walker, Carol F. Farver, Vibha N. Lama
Keizo Misumi, David S. Wheeler, Yoshiro Aoki, Michael P. Combs, Russell R. Braeuer, Ryuji Higashikubo, Wenjun Li, Daniel Kreisel, Ragini Vittal, Jeffrey Myers, Amir Lagstein, Natalie M. Walker, Carol F. Farver, Vibha N. Lama
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Research Article Pulmonology Transplantation

Humoral immune responses mediate the development of a restrictive phenotype of chronic lung allograft dysfunction

Abstract

Understanding the distinct pathogenic mechanisms that culminate in allograft fibrosis and chronic graft failure is key in improving outcomes after solid organ transplantation. Here, we describe an F1 → parent orthotopic lung transplant model of restrictive allograft syndrome (RAS), a particularly fulminant form of chronic lung allograft dysfunction (CLAD), and identify a requisite pathogenic role for humoral immune responses in development of RAS. B6D2F1/J (H2-b/d) donor lungs transplanted into the parent C57BL/6J (H2-b) recipients demonstrated a spectrum of histopathologic changes, ranging from lymphocytic infiltration, fibrinous exudates, and endothelialitis to peribronchial and pleuroparenchymal fibrosis, similar to those noted in the human RAS lungs. Gene expression profiling revealed differential humoral immune cell activation as a key feature of the RAS murine model, with significant B cell and plasma cell infiltration noted in the RAS lung allografts. B6D2F1/J lung allografts transplanted into μMt–/– (mature B cell deficient) or activation-induced cytidine deaminase (AID)/secretory μ-chain (μs) double-KO (AID−/−μs−/−) C57BL/6J mice demonstrated significantly decreased allograft fibrosis, indicating a key role for antibody secretion by B cells in mediating RAS pathology. Our study suggests that skewing of immune responses determines the diverse allograft remodeling patterns and highlights the need to develop targeted therapies for specific CLAD phenotypes.

Authors

Keizo Misumi, David S. Wheeler, Yoshiro Aoki, Michael P. Combs, Russell R. Braeuer, Ryuji Higashikubo, Wenjun Li, Daniel Kreisel, Ragini Vittal, Jeffrey Myers, Amir Lagstein, Natalie M. Walker, Carol F. Farver, Vibha N. Lama

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Figure 1

Murine orthotopic lung transplant model of F1 → parent (B6D2F1/J → C57BL/6J) strain combination develop chronic rejection.

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Murine orthotopic lung transplant model of F1 → parent (B6D2F1/J → C57BL...
Single left lung transplants were performed (isografts, B6D2F1/J → B6D2F1/J; RAS allografts, B6D2F1/J → C57BL/6J) and lung explants were either used to obtain lung homogenate (hydroxyproline and elastin assay) or were paraffin embedded for histology (H&E, trichrome and Picrosirius red staining). (A) Gross histopathology of control isograft and RAS allograft lungs, showing the transplanted lung on the left (L) and the native recipient lung on the right (R). The isografts were pink and inflated, while the allografts appeared dark and shrunken. (B) Quantitative assessment of fibrosis in lung allografts. Hydroxyproline content in graft lung homogenates was measured in triplicates and repeated twice (n = 10 isografts, 11 day 28 allografts, 9 day 40 allografts). Collagen staining intensity was measured in tissue sections stained with Picrosirius red using NIH ImageJ. Isografts (day 28), n = 6; RAS allografts (day 28), n = 7; RAS allografts (day 40), n = 6. Pleural collagen was detected in Masson’s trichrome–stained sections, and thickness of this collagen rind was measured using NIH ImageJ. n = 4 mice per group. One-way ANOVA with post hoc Dunnett’s. (C) Representative sections with H&E and trichrome staining (blue) demonstrating pleural and bronchovascular bundle fibrosis in allografts at day 28 and 40 after transplantation. n = 9 transplanted mice were used for histology in each group. Scale bars: 40 μm. (D) Elastica Van Gieson staining demonstrating elastin deposition along the pleura and interstitium in a day 40 allograft, compared with the isograft.(n = 5 isografts and 6 day 40 allografts). Scale bars: 300 μm. (E) Elastin was quantified in the transplant lungs harvested at day 28; n = 5 isografts and 6 RAS allografts. Unpaired, 2-tailed t test. Data are expressed as mean ± SEM.