ABSTRACT
We examined the in vivo behavior of liver natural killer T cells (NKT cells) by intravital fluorescence microscopic imaging of mice in which a green fluorescent protein cDNA was used to replace the gene encoding the chemokine receptor CXCR6. NKT cells, which account for most CXCR6(+) cells in liver, were found to crawl within hepatic sinusoids at 10-20 microm/min and to stop upon T cell antigen receptor activation. CXCR6-deficient mice exhibited a selective and severe reduction of CD1d-reactive NKT cells in the liver and decreased susceptibility to T-cell-dependent hepatitis. CXCL16, the cell surface ligand for CXCR6, is expressed on sinusoidal endothelial cells, and CXCR6 deficiency resulted in reduced survival, but not in altered speed or pattern of patrolling of NKT cells. Thus, NKT cells patrol liver sinusoids to provide intravascular immune surveillance, and CXCR6 contributes to liver-based immune responses by regulating their abundance.
Subject(s)
Killer Cells, Natural/immunology , Liver/enzymology , Receptors, Chemokine/immunology , Animals , Chemokine CXCL16 , Chemokine CXCL6 , Chemokines, CXC/genetics , Genes, Reporter , Green Fluorescent Proteins/genetics , Mice , Mice, Transgenic , Receptors, CXCR , Receptors, CXCR6 , Receptors, Chemokine/genetics , Receptors, Scavenger/geneticsABSTRACT
Although T helper (T(H)) cell-mediated immunity is required to effectively eliminate pathogens, unrestrained T(H) activity also contributes to tissue injury in many inflammatory and autoimmune diseases. We report here that the T(H) type 1 (T(H)1)-specific Tim-3 (T cell immunoglobulin domain, mucin domain) protein functions to inhibit aggressive T(H)1-mediated auto- and alloimmune responses. Tim-3 pathway blockade accelerated diabetes in nonobese diabetic mice and prevented acquisition of transplantation tolerance induced by costimulation blockade. These effects were mediated, at least in part, by dampening of the antigen-specific immunosuppressive function of CD4(+)CD25(+) regulatory T cell populations. Our data indicate that the Tim-3 pathway provides an important mechanism to down-regulate T(H)1-dependent immune responses and to facilitate the development of immunological tolerance.
