Role for CXCR6 in recruitment of activated CD8⁺ lymphocytes to inflamed liver

Hepatic infiltration of activated CD8 lymphocytes is a major feature of graft-vs-host disease (GvHD). Chemoattractant cytokines and their receptors are key regulators of lymphocyte trafficking, but the involvement of chemoattractant receptors in the physiologic recruitment of cells into the inflamed liver has not been defined. The present study examines the role of the chemokine receptor CXCR6, which is highly expressed by liver-infiltrating CD8 T cells. Hepatic accumulation of donor CD8, but not donor CD4, lymphocytes was significantly reduced in GvHD induced by transfer of CXCR6^-/-, H-2D^b lymphocytes into BDF₁, H-2D^bxd recipients. To determine whether altered recruitment contributes to the reduced accumulation, CXCR6 ^-/- or wild-type splenic lymphocytes participating in an active GvHD response were isolated and transferred i.v. into secondary recipients with active GvHD, and the short term (6-h) recruitment of transferred cells to the inflamed liver was assessed. CXCR6^-/- CD8 (but not CD4) cells displayed a significant (33%) reduction in liver localization, whereas frequencies in blood of CXCR6^-/- and wild-type CD8 cells were similar. Proliferation and apoptosis of liver-infiltrating donor CD8 cells were unaffected. We conclude that CXCR6 helps mediate the recruitment of activated CD8 lymphocytes in GvHD-induced hepatitis and may be a useful target to treat pathological inflammation in the liver.