A Protective Role of Donor B Cells against Ischemia-Reperfusion Injury in a Minor-Mismatched Mouse Lung Transplant Model

Abstract

<h3>Purpose</h3> We showed that recipient B cells are necessary for the development of chronic allograft fibrosis after ischemia-reperfusion injury (IRI) in a C57BL/10 (B10, H-2^b)-to-C57BL/6 (B6, H-2^b) minor alloantigen-mismatched mouse orthotopic lung transplant model. Whether donor-derived B cells play a specific role in this phenomenon is unknown. We hypothesized that donor B cells play a minimal role in the recipient. <h3>Methods</h3> We performed B10-to-B6 lung transplants with either prolonged (6h at 4°C followed by 45 min at 37°C and 15min anastomosis time) or minimal (1h at 4°C followed by 15min anastomosis time) antecedent storage using congenic donors and recipients. Donors were given anti-CD20 antibody or isotype control on day -2 (Fig 1A). Necropsies were performed at days +3 and +28. Allografts were histologically assessed in a blinded manner. Flow cytometry was used to evaluate immune cell populations at days 0 (pre-transplant donor samples), +3, and +28 (post-transplant samples). <h3>Results</h3> In the context of prolonged storage, anti-CD20 treatment was associated with early postoperative deaths not seen in the other groups (Fig 1B). At day 28, prolonged storage allografts exhibited fibrosis, with anti-CD20 treatment enhancing vascular fibrosis in surviving mice, but without impact on immune cell populations (Fig 1C). To better understand how anti-CD20 donor-treatment is impacting the allograft early post-transplant, we assessed the grafts at day 3: Both prolonged storage groups had severe IRI although, somewhat surprisingly, acute lung injury score was decreased by anti-CD20. Donor-derived B cells were reduced, and donor-derived neutrophils and monocytes were increased in the anti-CD20 group (Fig 1D). <h3>Conclusion</h3> Unexpectedly, our results suggest that donor-derived B cells have a protective role against IRI possibly via augmentation of neutrophils and monocytes in the donor graft. Further investigation is now underway.