Allogeneic CD4+CD25high T Cells Regulate Obliterative Bronchiolitis of Heterotopic Bronchus Allografts in Both Porcinized and Humanized Mouse Models

BACKGROUNDBronchiolitis obliterans syndrome is caused by a fibroproliferative process in lung allografts resulting in irreversible damage. In this study, we induced obliterative bronchiolitis and studied the contribution of regulatory T cells to its development in immune-deficient mice receiving heterotopic porcine bronchus transplants, and major histocompatibility complex-mismatched porcine peripheral blood mononuclear cell. Furthermore, we aimed to corroborate our findings in a humanized mouse model. METHODSHeterotopic bronchus transplantation was performed in 33 NOD.rag/γc mice, using miniature pigs as tissue donors. The recipient mice then either received saline (negative control), unsorted MHC-mismatched PBMC (positive control), PBMC enriched with CD4CD25 cells or PBMC depleted of CD4CD25 cells for reconstitution. The results were validated in 28 NOD.rag/γc mice undergoing heterotopic human bronchus transplantation and reconstitution with allogeneic human PBMC. RESULTSHistological lesions similar to those typical for obliterative bronchiolitis developed in vivo after reconstitution with allogeneic PBMC and were more severe in animals engrafted with PBMC depleted of CD4CD25 cells. In contrast, the group reconstituted with PBMC enriched with CD4CD25 cells showed well-preserved histology. The results of the humanized model confirmed those obtained in the porcinized model. CONCLUSIONSIn conclusion, both porcinized and humanized mouse models of heterotopic subcutaneous bronchus transplantation imitate the in vivo development of bronchiolitis obliterans syndrome–like lesions and reveal its sensitivity to T-cell regulation.