Modulation of CXCR1 and CXCR3 expression on NK cells via Tim-3 in a murine model of primary biliary cholangitis

Abstract

Tim-3, which is expressed on a variety of innate immune cells including NK cells, plays a key role in many autoimmune diseases. However, the immunomodulatory actions of Tim-3 on NK cells in primary biliary cholangitis (PBC) remain uncertain. Using a murine model of PBC we evaluated the expression of Tim-3 and its ligand Gal-9 in peripheral blood, liver, and spleen. Additionally, we studied Tim-3 regulation of chemokine receptors (CXCR1 and CXCR3) in vitro. Flow cytometric analysis indicated large numbers of infiltrating NK cells in the liver which exhibited high expression of Tim-3 and CXCR3. Moreover, we found overexpression of CXCR1 in liver tissue and liver-derived NK cells in PBC mice. We also observed lower levels of soluble Tim-3 in the serum of PBC mice. In vitro experiments with liver-derived NK cells from PBC mice indicated that CXCR3 was up-regulated by treatment with recombinant mouse TIM-3 Fc (rmTim-3 Fc) to activate the Tim-3 pathway. Furthermore, stimulating normal mouse spleen NK cells with poly I:C resulted in elevated expression of CXCR1 and interferon-γ release. Nonetheless, adding rmTim-3 Fc or rmGal-9 significantly down-regulated CXCR1 expression and IFN-γ release in NK cells activated by poly I:C, proposing a means to exploit the Tim-3 pathway to reverse responses in NK cells. In conclusion, our data demonstrate that dysregulation of Tim-3/Gal-9 is involved in modulating the local immune microenvironment in PBC mice. Our findings highlight the potential of Tim-3 pathway to modulate chemokine responses in NK cells during autoimmunity.

Keywords: CXCR1; CXCR3; NK cells; Primary biliary cholangitis; Tim-3.