Increased production of interferon-gamma by tumour infiltrating T lymphocytes in nasopharyngeal carcinoma: indicative of an activated status.

Undifferentiated nasopharyngeal carcinomas (UNPC) are characterised by an association with Epstein-Barr virus and an abundant lymphoid stroma. We studied the functional status of the infiltrating T cells in ten UNPC biopsies using an immunohistochemical approach. Twelve non-NPC biopsies were included as controls. Tumour cells of UNPC were positive for HLA class I (10/10) and II (8/10), LMP1 (3/10), and CD86 (6/10). Tumour infiltrating T cells (TILs) were detected with antibodies directed at CD3, CD4, and CD8, and shown to be comparable to that in the control biopsies. Although expression of CD28 was shown to be decreased in TILs, expression of CD25 and IFN-gamma at a relatively high percentage could be consistently detected in the UNPC biopsies. These data suggest that TILs in UNPC are in an activated status, and this T cell response is possibly directed at the tumour cells.