PDCD1 and hepatocellular carcinoma: In this setting, multidimensional flow cytometry analysis of human HCC-infiltrating lymphocytes reveals an enrichment of CD4+ T-cells [107] which involve unconventional activated cells expressing both activation markers, such as the inducible co-stimulatory molecule (ICOS), and inhibitory receptors such as T-cell immunoreceptor with Ig and ITIM domains (TIGIT) and PD-1.