Abstract

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.