Preferential production of IgG2 antibodies by parenchymal lung B-lymphocytes during lung allograft rejection

Zbtb7a induction in alveolar macrophages is implicated in anti-HLA-mediated lung allograft rejection

Chronic rejection significantly limits long-term success of solid organ transplantation. De novo donor-specific antibodies (DSAs) to mismatched donor human leukocyte antigen after human lung transplantation predispose lung grafts to chronic rejection. We sought to delineate mediators and mechanisms of DSA pathogenesis and to define early inflammatory events that trigger chronic rejection in lung transplant recipients and obliterative airway disease, a correlate of human chronic rejection, in mouse. Induction of transcription factor zinc finger and BTB domain containing protein 7a (Zbtb7a) was an early response critical in the DSA-induced chronic rejection. A cohort of human lung transplant recipients who developed DSA and chronic rejection demonstrated greater Zbtb7a expression long before clinical diagnosis of chronic rejection compared to nonrejecting lung transplant recipients with stable pulmonary function. Expression of DSA-induced Zbtb7a was restricted to alveolar macrophages (AMs), and selective disruption of Zbtb7a in AMs resulted in less bronchiolar occlusion, low immune responses to lung-restricted self-antigens, and high protection from chronic rejection in mice. Additionally, in an allogeneic cell transfer protocol, antigen presentation by AMs was Zbtb7a-dependent where AMs deficient in Zbtb7a failed to induce antibody and T cell responses. Collectively, we demonstrate that AMs play an essential role in antibody-induced pathogenesis of chronic rejection by regulating early inflammation and lung-restricted humoral and cellular autoimmunity.

IL-17-dependent cellular immunity to collagen type V predisposes to obliterative bronchiolitis in human lung transplants

Bronchiolitis obliterans syndrome (BOS), a process of fibro-obliterative occlusion of the small airways in the transplanted lung, is the most common cause of lung transplant failure. We tested the role of cell-mediated immunity to collagen type V [col(V)] in this process. PBMC responses to col(II) and col(V) were monitored prospectively over a 7-year period. PBMCs from lung transplant recipients, but not from healthy controls or col(IV)-reactive Goodpasture's syndrome patients after renal transplant, were frequently col(V) reactive. Col(V)-specific responses were dependent on both CD4+ T cells and monocytes and required both IL-17 and the monokines TNF-alpha and IL-1beta. Strong col(V)-specific responses were associated with substantially increased incidence and severity of BOS. Incidences of acute rejection, HLA-DR mismatched transplants, and induction of HLA-specific antibodies in the transplant recipient were not as strongly associated with a risk of BOS. These data suggest that while alloimmunity initiates lung transplant rejection, de novo autoimmunity mediated by col(V)-specific Th17 cells and monocyte/macrophage accessory cells ultimately causes progressive airway obliteration.