Development of bronchiolitis obliterans syndrome (BOS), chronic lung allograft rejection, is a major obstacle to long-term success from lung transplantation. De novo antibodies (Abs) to mismatched donor HLA are strongly associated with development of BOS. In experimental mouse model of obliterative airway disease (OAD), we have identified metallothionein 1 (Mt1) as one of the early genes induced following ligation of MHC with specific Ab. Metallothioneins are known to participate in heavy metal detoxification and suppress regulatory T cell differentiation. In this study, we examined effector function(s) of Mt1 in anti-MHC induced murine OAD. We determined development of OAD and immune responses to lung-associated self-antigens (SAgs), K alpha 1 Tubulin (Ka1T) and Collagen V (ColV), following MHC class I ligation by anti-MHC in Mt1 deficient (Mt1^-/-) mice. Mt1^-/- and WT mice were administered intrabronchially with anti-H-2K^b or isotype control Abs for 30 days and evaluated for small airway obstruction and fibrosis by histopathology, and elicitation of immune responses to lung associated antigens (Ka1T and ColV) by ELISA and ELISPOT. Frequency of regulatory T cells (CD49b⁺ and LAG3⁺) in lungs was quantitated by multicolor flow cytometry and production of IL-10 by lung leukocytes was assessed by quantitative PCR and luminex assays. MHC class I Ab (H-2K^b) significantly reduced OAD in Mt1^-/-, bronchiolar obstruction, epithelial hyperplasia and peribronchiolar fibrosis were similar to isotype control. Anti-H-2K^b administered WT mice, on the other hand, demonstrated bronchiolar obstruction compared to that of isotype control. Concomitantly, MHC class I ligation in WT induced higher Ka1T and ColV specific auto-Abs, and IL-17 and IFN-γ secreting T cells compared to that in Mt1^-/-. Further analysis of the regulatory T cells indicated a reverse trend; higher accumulation of regulatory T cells and greater IL-10 response was found in Mt1^-/- over WT. Overall, loss of Mt1 abrogated anti-MHC induced OAD and resulted in significantly lesser Abs and T cell responses to lung SAgs. Using a murine model of anti-MHC induced OAD, we have identified Mt1, an important player, involved in the early inflammation and pathogenesis. In this model, functional loss of Mt1 reduced pathologic propensity induced by anti-MHC and conferred protection by eliciting anti-inflammatory cytokine and regulatory T cells.

CITATION INFORMATION: Nayak D, Zhou F, Benshoff N, Mohanakumar T. Metallothionein Accelerates Anti-MHC Induced Small Airway Obliteration and Fibrosis by Negatively Regulating IL-10 and Regulatory Cells. Am J Transplant. 2016;16 (suppl 3).

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