Skip to main content

Functional Biology of Hepatic CD8+ T cells

Periodic Reporting for period 2 - FATE (Functional Biology of Hepatic CD8+ T cells)

Reporting period: 2019-01-01 to 2020-06-30

CD8+ T cells have a key role in eliminating intracellular pathogens and tumors that affect the liver. The protective capacity of these cells relies on their ability to migrate to and traffic within the liver, recognize pathogen- or tumor-derived antigens, get activated and deploy effector functions. While some of the rules that characterize CD8+ T cell behavior in the infected and cancerous liver have been characterized at the population level, we have only limited knowledge of the precise dynamics of intrahepatic CD8+ T cell conduct at the single-cell level. In preliminary data for this project we have developed several advanced imaging techniques that allow us to dissect the interactive behavior of CD8+ T cells within the mouse liver at an unprecedented level of spatial and temporal resolution. We predict that this approach, combined with unique models of hepatitis B virus pathogenesis and a new model of hepatocellular carcinoma created ad hoc for this proposal, will generate novel mechanistic insights into the spatiotemporal determinants that govern the capacity of CD8+ T cells to home and function in the virus- or tumor-bearing liver. Specifically, we plan to pursue two main goals: 1) To assess how the anatomical, hemodynamic and environmental cues that characterize hepatocellular carcinomas shape CD8+ T cell behavior and function; 2) To characterize intrahepatic T cell priming events that induce functionally defective T cell responses. Results emerging from these studies will advance our knowledge on how adaptive immunity mediates pathogen clearance and tumor elimination. This new knowledge may lead to improved vaccination and treatment strategies for immunotherapy of infectious diseases and cancer.
CD8+ T cells have a key role in eliminating intracellular pathogens and tumors that affect the liver. The protective capacity of these cells relies on their ability to migrate to and traffic within the liver, recognize pathogen- or tumor-derived antigens, get activated and deploy effector functions. While some of the rules that characterize CD8+ T cell behavior in the infected and cancerous liver have been characterized at the population level, up until the execution we had only limited knowledge of the precise dynamics of intrahepatic CD8+ T cell conduct at the single-cell level.
In data that have been recently published in Nature (Benechet et al., Nature 2019), we have now shown that priming by Kupffer cells, which are not natural targets of hepatitis B, leads to differentiation of CD8+ T cells into effector cells that form dense, extravascular clusters of immotile cells scattered throughout the liver. By contrast, priming by hepatocytes, which are natural targets of hepatitis B, leads to local activation and proliferation of CD8+ T cells but not to differentiation into effector cells; these cells form loose, intravascular clusters of motile cells that coalesce around portal tracts. Transcriptomic and chromatin accessibility analyses reveal unique features of these dysfunctional CD8+ T cells, with limited overlap with those of exhausted or tolerant T cells; accordingly, CD8+ T cells primed by hepatocytes cannot be rescued by treatment with anti-PD-L1, but instead respond to IL-2. These findings suggest immunotherapeutic strategies against chronic hepatitis B infection.
We have completed Aim 2 and are now tackling full force Aim 1 which we expect to complete before the end of the funding period.