ABSTRACT
CD1d-restricted invariant natural killer T (iNKT) cells are known as potent early regulatory cells of immune responses. Besides the established roles in the regulation of inflammation and autoimmune disease, studies have shown that iNKT cells have important roles in tumor surveillance and the control of tumor metastasis. Here we found that the absence of iNKT cells markedly decreased the total number of intestinal polyps in APCMin/+ mice, a model for colorectal cancer. Polyp iNKT cells were enriched for interleukin-10 (IL-10)- and IL-17-producing cells, showed a distinct phenotype being CD4+, NK1.1- CD44int, and PD-1lo, and they were negative for the NKT cell transcription factor promyelocytic leukemia zinc-finger. The absence of iNKT cells was associated with a reduced frequency of regulatory T (Tregs) cells and lower expression levels of FoxP3 protein and transcript uniquely in the polyps, and a switch to an inflammatory macrophage phenotype. Moreover, in iNKT cell-deficient APCMin/+ mice, expression of T-helper (TH) 1-associated genes, such as IFN-γ and Nos2, was increased in polyps, concomitantly with elevated frequencies of conventional CD4+ and CD8+ T cells in this tissue. The results suggest that a population of regulatory iNKT cells locally promote intestinal polyp formation by enhancing Treg cells and immunosuppression of antitumor TH1 immunity.
Subject(s)
Colorectal Neoplasms/immunology , Intestines/immunology , Natural Killer T-Cells/immunology , Polyps/immunology , T-Lymphocytes, Regulatory/immunology , Th1 Cells/immunology , Adenomatous Polyposis Coli Protein/genetics , Animals , Disease Models, Animal , Forkhead Transcription Factors/metabolism , Humans , Immunosuppression Therapy , Interferon-gamma/metabolism , Intestines/pathology , Lymphocyte Activation , Lymphocyte Count , Mice , Mice, Mutant Strains , Mutation/geneticsABSTRACT
The endogenous glycosphingolipid sulfatide is a ligand for CD1d-restricted type II natural killer T (NKT) lymphocytes. Through the action of these cells,sulfatide treatment has been shown to modulate the immune response in mouse models for autoimmune diseases, infections and tumour immunity. Sulfatide exists naturally in different organs including the pancreas, where sulfatide colocalizes with insulin within the Langerhans islet b-cells, targets for the immune destruction in type 1 diabetes (T1D). Human T1D patients, but not patients with type 2 diabetes nor healthy individuals, have autoantibodies against sulfatide in serum, suggesting that sulfatide induces an immune response in the natural course of T1D in humans. Here, we investigate sulfatide as an autoantigen and a modulator of autoimmune disease in the murine model forT1D, the non-obese diabetic (NOD) mice. We demonstrate that aged NOD mice displayed serum autoantibody reactivity to sulfatide; however, this reactivity did not correlate with onset of T1D. Repeated administration of sulfatide did not result in an increase in serum reactivity to sulfatide. Moreover, a multidose sulfatide treatment of female NOD mice initiated at an early (5 weeks of age),intermediate (8 weeks of age) or late (12 weeks of age) phase of T1D progression did not influence the incidence of disease. Thus, we demonstrate that a fraction of NOD mice develop autoantibody reactivity to sulfatide; however, we fail to demonstrate that sulfatide treatment reduces the incidence of T1D in this mouse strain.
