Expression of inhibitory natural killer receptors on tumor-infiltrating CD8+ T lymphocyte lineage in human endometrial carcinoma

To investigate the expression of natural killer receptors (NKRs) within the human tumor milieu, we directly examined the in vivo expressions of various NKRs on tumor-infiltrating lymphocytes (TILs) derived from human endometrial carcinoma (EC). In total, 22 patients with stage IA-IIIA EC were enrolled. TILs were isolated from tissue specimens by means of a mechanical dispersal technique. The subpopulations of immunocytes were quantified, and expressions of NKRs on CD8+ T cells were analyzed by triple-color flow cytometry. CD8+ T cells express higher ratios of CD94 and NKG2A in TILs than in peripheral blood mononuclear cells (PBMCs) in human EC. Flow cytometry reveals that 15.90% of CD3+CD8+ TILs compared with 2.10% of CD3+CD8+ PBMCs express the NKG2A molecules (P < 0.001). The percentage expressions of CD94 are 8.40% in CD3+CD8+ TILs and 3.80% in CD3+CD8+ PBMCs (P= 0.013). The numbers of CD8+ T cells expressing CD158b and NKB1 are higher in CD3+CD8+ PBMCs in EC than in normal (CD158b: 10.70% vs 2.60%, P < 0.001; NKB1: 2.20% vs 0.40%, P= 0.018, respectively). Increased expression of CD94/NKG2A restricted to tumor-infiltrating CD8+ T cell subsets may shape the cytotoxic responses, which indicate a possible role of tumor escape from host immunity in human EC.