Tertiary lymphoid organs drive disrupted gut to lymph node communication through association with collecting lymphatic vessels

Abstract

Abstract The concept that impaired lymphatic flow during the progression of Crohn’s disease, a major form of inflammatory bowel disease, emerged decades ago, but remains unresolved. In Crohn’s disease, tertiary lymphoid organs (TLOs) are associated with collecting lymphatic vessels (CLVs) of the mesentery that govern lymph outflow from the intestine. Whether TLOs affect lymph transport is unknown. In the TNFDARE mouse model of Crohn’s-like ileitis, TLOs formed at valve regions which supported lymphangiogenic outgrowths to the TLOs. Photoconversion approaches to study cell trafficking indicated that TLOs received immune cells traveling from the intestine but scarcely allowed their egress, effectively trapping DCs, B, and T cells. Using adoptive transfer of microbiota-dependent TCR we found reduced overall Tregs differentiation and their presence shifted from the lymph nodes to TLOs, altering intestinal-induced responses. Strikingly, although anti-TNF therapy dampens gut inflammation, TLO are refractory the therapy. Moreover, passage of soluble fluorescent tracer through TLO-rich CLVs was also impeded, indicating transport defects were intrinsic to the CLVs. Indeed, lymph flow diverted at TLO to neighboring CLV branches, where dysfunctional valves allowed lymph return to the gut wall, accompanied by lymph leakage at the TLOs. Culturing lymphatic endothelial cells with TNF demonstrate that the cytokine alone can reduce key genes found in lymphatic valves. These data indicate that TNF disrupts lymphatic valve maintenance pathways, promoting formation of mesenteric TLOs that broadly impair lymph transit of molecules and cells from the intestine, impairing immune surveillance of the mucosal barrier, altering homeostasis.