HUMAN MONOCYTES ENHANCE INTESTINAL STEM CELL (ISC) SURVIVAL

Introduction: Innate lymphoid cells (ILC) are innate immune cells, which is classified into ILC1, ILC2 and ILC3, each of which play an important role in maintaining intestinal homeostasis through rapid immune response to pathogens.In addition, there have been no data about dynamics of ILC and it is still controversial that ILC move between organs through vascular or lymphoid vessels.We have established the method to analyze lymphoid cells flowing in the intestinal lymph by cannulating tubes into lymphatic duct (J Leucocyte Biol 2001).We aimed to clarify how each subset of ILC draining from intestinal mucosa to MLNs by using this system.In addition, changes of subset of ILC in small intestinal lamina propria lymphocytes (SI-LPL) and MLNs were investigated in several intestinal inflammation models.Methods: (1) Wistar male rats were used to collect the lymph fluids by cannulating the thoracic duct.In some rats (5 weeks), mesenteric lymphadenectomy (MLNx) was performed to make lymph fistula, and then thoracic duct was cannulated 4weeks later.Thoracic duct lymphocytes (TDL) were collected for a day (~10 7 cells) restrained in the Bollmann cage and analyzed by flow cytometory.(2) We used three models of inflamed intestine; emulsifier-induced diarrheal enteritis, ovalbumin (OVA)-induced allergic enteritis, and indomethacin (IND)-induced enteritis.C57BL/6J and BALB/c mice were used.A kind of emulsifier polisorbate 80 (P80), known to cause chronic intestinal inflammation, was taken by drinking water (1.0 % v/w) for 8 weeks.Allergic enteritis was induced by OVA.IND (5mg/kg, i.p.) was administered for two days.We examined the compositional change of ILC of SI-LPL and MLNs in each model by flow cytometory.Results: (1) Although percentage was small (less than 0.01% of TDL), we identified ILC directly in the lymph in normal rat.Four weeks after MLNx, we could obtain more ILC, which composed 0.1% of total TDL including mainly ILC1 and ILC3.ILC2 was increased in inflamed condition induced by IND.(2)Total ILC composed about 3.0% of SI-LPL in control mice.In P80induced enteritis, total ILC increased to about 4.4%, among which ILC1 increased along with significant increase of ILC1 in MLNs.In OVA-induced enteritis, total ILC increased in SI-LPL and MLNs, among which inflammatory ILC2 (ST2 -KLRG high ILC2) increased dramatically.In IND-induced enteritis, although total ILC decreased in SI-LPL, all subsets significantly increased in MLNs.Conclusions: We identified for the first time ILC in TDL.Dramatic increase in the number of ILCs after removal of MLNs suggested that ILC efflux from intestinal mucosa to MLNs through lymphatics physiologically.Changes in composition