Tertiary Lymphoid Organs promote allograft rejection

Abstract Tertiary lymphoid organs (TLOs) are ectopic lymphoid structures that arise in non-lymphoid tissues and are frequently observed in tissue affected by non-resolving chronic inflammation. If TLOs are beneficial or detrimental in transplantation is controversial. We investigate the role of TLO and LTbR in transplantation by manipulating the LTa-LTbR pathway. Using a mouse allo kidney transplantation model, we found that preformed intragraft TLO are sufficient to precipitate rejection in recipients lacking all secondary lymphoid organs (SLO)(LTbRko). In WT recipients with a complete set of SLO, intragraft TLO accelerated rejection (MST=63 vs. 225 d). Donor grafts that cannot form TLO (LTbRko) prolonged allograft survival (MST 24 vs 11 d) in an acute kidney rejection model. Intravital imaging confirmed that T and B cell activation takes place in renal TLO upon migration of naïve T and B cells and prolonged interactions with dendritic cells. T cells produced IFNg and Confetti+/+ B cells clonally expanded within TLO. In summary, intragraft TLO are sufficient for and accelerate allograft rejection. Local immune responses are initiated and maintained in intragraft TLO, while disruption of TLO formation in the allograft leads to prolonged allograft survival. TLO support T and B cell activation as well as local DSA formation. These findings highlight the importance of TLO in local immune responses with implications for cancer, autoimmunity and transplantation.