Background:: Ileal involvement in Crohn's disease (CD) is associated with NOD2 mutations and granulocyte‐macrophage colony stimulating factor autoantibodies (GM‐CSF Ab), and GM‐CSF blockade promotes ileitis in Nod2/Card15‐deficient (C15KO) mice. RALDH2‐expressing dendritic cells (DC) and IL‐4 promote CCR9 imprinting and small bowel homing of T lymphocytes, in conjunction with CCL25 expression by ileal epithelial cells (IEC). We hypothesized that GM‐CSF neutralization promotes ileal disease by modulating expression of CCL25 by IEC and CCR9 by T lymphocytes via Nod2‐dependent and independent pathways.
Methods:: CCL25 and CCR9 expression were determined in pediatric CD patients stratified by GM‐CSF Ab. Ileitis was induced in C15KO mice via GM‐CSF Ab administration followed by nonsteroidal antiinflammatory drug (NSAID) exposure, and expression of CCL25, CCR9, FOXP3, intracellular cytokines, and RALDH2 was determined in IEC and immune cell populations.
Results:: The frequency of CCL25+ IEC and CCR9+ T lymphocytes was increased in CD patients with elevated GM‐CSF Ab. In the murine model, GM‐CSF blockade alone induced IEC CCL25 expression, and reduced the frequency of mesenteric lymph node (MLN) CD4+FOXP3+ cells, while Card15 deficiency alone enhanced MLN DC RALDH2 expression. Both GM‐CSF neutralization and Card15 deficiency were required for downregulation of MLN DC IL‐10 expression; under these conditions NSAID exposure led to an expansion of IL‐4+ and IL‐17+ CCR9+ lymphocytes in the ileum.
Conclusions:: GM‐CSF prevents ileal expansion of CCR9+ lymphocytes via Nod2‐dependent and independent pathways. CCR9 blockade may be beneficial in CD patients with elevated GM‐CSF Ab.
1 Gastroenterology, Hepatology, and Nutrition, Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, Ohio
2 Pulmonary Biology, Cincinnati Children's Hospital Medical Center and the University of Cincinnati College of Medicine, Cincinnati, Ohio
*Reprints: MLC 2010, 3333 Burnet Ave., Cincinnati, OH 45229
Received 5 January 2011; Accepted 12 January 2011
Published online 4 March 2011 in Wiley Online Library (wileyonlinelibrary.com).
Grant sponsor: Crohn's and Colitis Foundation of America; Grant sponsor: Broad Medical Research Program; Grant sponsor: AGA Foundation for Digestive Health and Nutrition; Grant sponsor: Integrative Morphology and Flow Cytometry cores of the National Institutes of Health (NIH)‐supported Cincinnati Children's Hospital Research Foundation Digestive Health Center; Grant Number: 1P30DK078392‐01; Grant sponsor: NIH; Grant Numbers: T32 DK07727 R01 DK078683 R01 DK068164.
Supported by the Crohn's and Colitis Foundation of America (to L.A.D.), the Broad Medical Research Program (to L.A.D.), AGA Foundation for Digestive Health and Nutrition (to C.M.S.), the Integrative Morphology and Flow Cytometry cores of the National Institutes of Health (NIH)‐supported Cincinnati Children's Hospital Research Foundation Digestive Health Center (1P30DK078392‐01), and NIH grants T32 DK07727 (to C.M.S), R01 DK078683 (to L.A.D.) and R01 DK068164 (to L.A.D.).
This work was previously presented in abstract form at the 2009 Digestive Diseases Week and CCFA Advances in IBD Meetings.