Roles of the programmed cell death 1, T cell immunoglobulin mucin-3, and cluster of differentiation 288 pathways in the low reactivity of invariant natural killer T cells after chronic hepatitis B virus infection.

Abstract

One of the main responses of invariant natural killer T (iNKT) cells to antigen stimulation is the rapid production of interleukin (IL)-4 and interferon (IFN)-γ cytokines. There is a decline in the function of iNKT cells in chronic hepatitis B (CHB) patients. In this study, we explored the impact of programmed cell death 1 (PD-1), T cell immunoglobulin mucin-3 (Tim-3), and cluster of differentiation 28 (CD28) expression on iNKT cell functions in CHB patients. Flow cytometry was used to test iNKT frequencies and levels of PD-1, Tim-3, CD28, IL-4, and IFN-γ secreted by iNKT cells. An enzyme-linked immunosorbent assay (ELISA) was used to measure IL-4 and IFN-γ secretion upon α-galactosylceramide (α-GalCer) activation ex vivo. We found that the levels of expression of PD-1 and Tim-3 from iNKT cells in CHB patients were significantly higher than in healthy donors (p<0.05), but there was lower expression of CD28 (p<0.05) and an impaired capability to produce IL-4 and IFN-γ (p<0.05). In vitro α-GalCer stimulation upregulated the expression of PD-1(+) iNKT cells (p<0.05), Tim-3(+) iNKT cells (p<0.05), and CD28(+) iNKT cells (p<0.05). In response to combination therapies consisting of α-GalCer and anti-PDL1 monoclonal antibody (mAb) and/or anti-Tim-3 mAbs and/or anti-CD80/anti-CD28 mAbs, IL-4(+) and IFN-γ(+) iNKT cells demonstrated different degrees of growth (p<0.05). The functional decline of iNKT cells was closely related to the decrease in CD28 expression and the increases of Tim-3 and PD-1. In addition, clinical antiviral treatment with lamivudine could partially restore the immune function of iNKT cells in CHB patients.