Liver environment and HCV replication affect human T-cell phenotype and expression of inhibitory receptors

Abstract

Background & aims: There is an unclear relationship between inhibitory receptor expression on T cells and their ability to control viral infections. Studies of human immune cells have been mostly limited to T cells from blood, which is often not the site of infection. We investigated the relationship between T-cell location, expression of inhibitory receptors, maturation, and viral control using blood and liver T cells from patients with hepatitis C virus (HCV) and other viral infections.

Methods: We analyzed 36 liver samples from HCV antibody-positive patients (30 from patients with chronic HCV infection, 5 from patients with sustained virological responses to treatment, and 1 from a patient with spontaneous clearance) with 19 paired blood samples and 51 liver samples from HCV-negative patients with 17 paired blood samples. Intrahepatic and circulating lymphocytes were extracted; T-cell markers and inhibitory receptors were quantified for total and virus-specific T cells by flow cytometry.

Results: Levels of the markers PD-1 and 2B4 (but not CD160, TIM-3, or LAG-3) were increased on intrahepatic T cells from healthy and diseased liver tissues compared with T cells from blood. HCV-specific intrahepatic CD8(+) T cells from patients with chronic HCV infection were distinct in that they expressed TIM-3 along with PD-1 and 2B4. In comparison, HCV-specific CD8(+) T cells from patients with sustained virological responses and T cells that recognized cytomegalovirus lacked TIM-3 but expressed higher levels of LAG-3; these cells also had different memory phenotypes and proliferative capacity.

Conclusions: T cells from liver express different inhibitory receptors than T cells from blood, independent of liver disease. HCV-specific and cytomegalovirus-specific CD8(+) T cells can be differentiated based on their expression of inhibitory receptors; these correlate with their memory phenotype and levels of proliferation and viral control.

Keywords: CMV; Costimulation; HCV; IHL; Immune Regulation; Inflammation; PBMC; T-Cell Exhaustion; cytomegalovirus; hepatitis C virus; intrahepatic lymphocyte; peripheral blood mononuclear cell.