XCL1 and viral infectious disease: The Gene ontology based two datasets of different expression genes (XCL1+ CD8+ T cell vs all other cells (including hepatocytes, B cell, NK, etc.); XCL1+ CD8+ T cell vs other CD8+ T cells), also supported that XCL1+ CD8+ T cells play a key role in anti-tumor immunity, specifically in HCC patients with virus infections (Figure 2d).