RESUMO
Lung transplant remains the primary therapeutic option for patients with end-stage lung disease, but long-term survival rates remain suboptimal compared with other solid organ transplants. Acute cellular rejection (ACR) is a significant challenge in lung transplant recipients, with T cell-mediated mechanisms playing a major role. IL-10 is known for its immunoregulatory function, although its specific role in lung allograft rejection remains unclear. Using the mouse orthotopic lung transplant model, we investigated the role of IL-10 in regulating alloeffector T cell responses. Unexpectedly, we found that IL-10 was not required for early costimulation blockade-induced allograft acceptance. However, IL-10 deficiency or blockade resulted in increased CD4+ T cell numbers, proliferation, graft infiltration, and alloeffector responses. In the absence of IL-10, CD4+ T cell responses predominated over CD8 responses during ACR in contrast to wild-type mice. Type 1 immunity (IFN-γ) responses along with elevated CD4+NKG7+ and CD4+CD107a+ responses predominated during ACR, highlighting a critical regulatory role for IL-10 in modulating CD4+ T cell alloimmune responses. We further demonstrated increased colocalization of NKG7 and CD107a in CD4+ T cells from IL-10-deficient allografts, suggesting coordination in cytotoxic activity. Together, our findings highlight a critical role for IL-10 in regulation of cytotoxic CD4+NKG7+ T cells, an effector population that needs further investigation to elucidate their role in lung allograft rejection.
Assuntos
Aloenxertos , Rejeição de Enxerto , Interleucina-10 , Transplante de Pulmão , Animais , Camundongos , Aloenxertos/imunologia , Linfócitos T CD4-Positivos/imunologia , Rejeição de Enxerto/imunologia , Sobrevivência de Enxerto/imunologia , Interferon gama/imunologia , Interferon gama/metabolismo , Interleucina-10/imunologia , Interleucina-10/metabolismo , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Linfócitos T Citotóxicos/imunologiaRESUMO
Chronic lung allograft dysfunction is the major barrier to long-term survival in lung transplant recipients. Evidence supports type 1 alloimmunity as the predominant response in acute/chronic lung rejection, but the immunoregulatory mechanisms remain incompletely understood. We studied the combinatorial F-box E3 ligase system: F-box protein 3 (FBXO3; proinflammatory) and F-box and leucine-rich repeat protein 2 (FBXL2; anti-inflammatory and regulates TNFR-associated factor [TRAF] protein). Using the mouse orthotopic lung transplant model, we evaluated allografts from BALB/c â C57BL/6 (acute rejection; day 10) and found significant induction of FBXO3 and diminished FBXL2 protein along with elevated T-bet, IFN-γ, and TRAF proteins 1-5 compared with isografts. In the acute model, treatment with costimulation blockade (MR1/CTLA4-Ig) resulted in attenuated FBXO3, preserved FBXL2, and substantially reduced T-bet, IFN-γ, and TRAFs 1-5, consistent with a key role for type 1 alloimmunity. Immunohistochemistry revealed significant changes in the FBXO3/FBXL2 balance in airway epithelia and infiltrating mononuclear cells during rejection compared with isografts or costimulation blockade-treated allografts. In the chronic lung rejection model, DBA/2J/C57BL/6F1 > DBA/2J (day 28), we observed persistently elevated FBXO3/FBXL2 balance and T-bet/IFN-γ protein and similar findings from lung transplant recipient lungs with chronic lung allograft dysfunction versus controls. We hypothesized that FBXL2 regulated T-bet and found FBXL2 was sufficient to polyubiquitinate T-bet and coimmunoprecipitated with T-bet on pulldown experiments and vice versa in Jurkat cells. Transfection with FBXL2 diminished T-bet protein in a dose-dependent manner in mouse lung epithelial cells. In testing type 1 cytokines, TNF-α was found to negatively regulate FBXL2 protein and mRNA levels. Together, our findings show the combinatorial E3 ligase FBXO3/FBXL2 system plays a role in the regulation of T-bet through FBXL2, with negative cross-regulation of TNF-α on FBXL2 during lung allograft rejection.