Dextran sulphate sodium increases splenic Gr1(+)CD11b(+) cells which accelerate recovery from colitis following intravenous transplantation

While Gr1(+)CD11b(+) cells are known to regulate immune responses and accumulate in most cancer tissues, the function of Gr1(+)CD11b(+) cells in inflammation is poorly understood. We investigated the role of Gr1(+)CD11b(+) cells in a dextran sulphate sodium (DSS)-treated mouse model of ulcerative colitis (UC). C57BL/6 mice were treated with 2% DSS in drinking water for 5 days. Disease progression and recovery were assessed by body weight, disease activity index score (DAI) score and colon length. Splenic Gr1(+)CD11b(+) cell number was greatly increased during the recovery phase of DSS-induced colitis. DSS-derived splenic Gr1(+)CD11b(+) cells were administered intravenously to recipient (C57BL/6) mice during the early phase of DSS treatment. The transplanted splenic DSS-induced Gr1(+)CD11b(+) cells improved DSS-induced colitis and promoted efficient colonic mucosal healing. We found that the CD11b(+) single positive cells increased in the course of DSS-induced colitis in lamina propria. The transplantation of splenic Gr1(+)CD11b(+) cells induced feedback suppression of myeloid-lineage cell development. Namely, the transplantation of splenic Gr1(+)CD11b(+) cells greatly suppressed the migration of CD11b(+) single positive cells to the lamina propria. Further, transplantation of Gr-1(+)CD11b(+) cells greatly suppressed the increase of the same population, especially during the late phase of DSS colitis both in spleen and bone marrow.