Memory T-lymphocytes are the main population of tumor-infiltrating lymphocytes obtained from human primary liver tumors.

The phenotypic characteristics of freshly isolated tumor-infiltrating lymphocytes (TIL) obtained from human liver tumors were analyzed by two-color flow cytometry. TIL consisted of mainly CD3+ T-lymphocytes (70-80%). The ratio of CD4/CD8 in TIL from primary and metastatic liver tumors and autologous peripheral blood lymphocytes (A-PBL) was 1.3, 1.1 and 1.3, respectively. The majority of CD3+ T-lymphocytes (mean +/- SD; 95 +/- 11%) expressed T-cell antigen receptor (TCR) alpha/beta, and gamma/delta TCR positive T-cells were only 5 +/- 4.5% in TIL from both primary and metastatic liver tumors. TIL showed significantly higher percentages of transient activation markers, such as CD25 (Tac) and HLA-DR, than A-PBL. TIL also contained significantly more populations of CD3+ CD45RO+ T-lymphocytes, which are considered to be expressed on primed (memory) T-lymphocytes, than A-PBL. Furthermore, TIL from primary liver tumors demonstrated significantly higher percentages of CD3+ CD45RO+ T-cells than those from metastatic liver tumors. These data indicate that TIL from human liver tumors are an apparently distinct population from A-PBL, and that local immune responses against human primary and metastatic liver tumors might be different. Moreover, TIL from primary liver tumors consisted of mainly activated or primed (memory) T-cells, suggesting that they were sensitized and activated by autologous tumor cells in vivo. These observations may imply the possibility of adoptive immunotherapy using TIL against human primary liver tumors.