OBSTRUCTED LYMPHATIC TRANSPORT AND LEAKAGE DRIVEN BY MESENTERIC TERTIARY LYMPHOID ORGANS IS A FEATURE OF CROHN’S DISEASE MOUSE MODEL

Abstract

Abstract Pioneer reports of Crohn’s disease (CD) suggested that impaired lymphatic flow might drive its pathogenesis but remains unsettled. Nodules of tertiary lymphoid organs (TLO) are found in association with collecting lymphatic vessels (CLVs) of the mesentery that normally conducts lymph outflow from the intestine. Whether TLOs affect lymph transport is unknown. In the TNFΔARE mouse model of Crohn’s-like ileitis, TLOs are found in valves regions. Using lymphatic reporters and photoconversion to study cell trafficking from the intestine, our findings indicated that TLOs halts immune cells traveling from the inflamed ileum to the lymph node, effectively trapping DCs, B, and T cells, and impacting the development of microbe tolerogenic regulatory T cells. Lymphatic transport defects were intrinsic to the CLVs because the soluble fluorescent tracer’s passage through TLO was also blocked. Lymph blockage promoted retrograde lymphatic flow returning towards the gut wall due to incapable valves. Moreover, significant lymph leakage was found, specifically at the TLOs. Neutralizing anti-TNF mAb treatment into TNFΔARE mice is ineffective in eliminating TLOs or restoring lymphatic trafficking when administered in female mice with advanced disease. In males, the therapy was able to restore forward flow to the lymph node. However, even in the presence of TNF inhibition, both sexes demonstrated TLO lymph leakage. Thus, mesenteric TLOs that form during chronic ileitis drive broadly impaired lymph transit of molecules and cells from the intestine that is only partially reversible by neutralizing the cytokine cascade underlying the disease and establish a perennial tissue alteration.