The purpose of the present study was to investigate the role of latency-associated peptide (LAP)⁺CD4⁺T cells in hepatocellular carcinoma (HCC) immunity. Flow cytometric analysis was performed to detect the proportion of LAP⁺CD4⁺ T cells among the peripheral blood mononuclear cells (PBMCs) of 30 HBV-infected HCC patients at the pre-operative and post-operative stages, as well as 30 hepatitis B virus (HBV)-infected volunteers as a control group. Furthermore, tumor tissues and peri-tumor tissues from 28 patients with HCC, as well as hepatic tissues from 28 HBV-infected patients with benign lesions were subjected to immunohistochemical analysis with double staining for LAP and CD4, and the average number of the LAP⁺CD4⁺T cells in each visual field was quantified. The results indicated that the proportion of LAP+CD4+ T cells in the PBMCs of patients with HCC was significantly higher than that in the control group (1.84±0.85 vs. 0.73±0.39%, P=0.019), while it was significantly reduced after the operation (1.07±0.35, P=0.021), but still slightly, if not significantly, higher compared with that in the control group (P=0.342). Furthermore, the number of LAP⁺CD4⁺ T cells per high-magnification microscopic field (magnification, ×400) in the HCC tissues was 11.25±3.00, which was significantly higher than that in the peri-cancer tissues (5.75±1.00) and that in the HBV-infected hepatic tissues around benign lesions (2.61±0.83). In peri-cancer tissues, LAP⁺CD4⁺ T cells were also significantly more abundant than in control tissues. Furthermore, in the HCC tissues, LAP⁺CD4⁺ T cells were present as clusters in the tumor stroma and closely associated with CD4⁺ T lymphocytes. By contrast, in the peri-cancer liver tissues and HBV-infected hepatic tissues around benign lesions, LAP⁺CD4⁺ T cells were sparsely distributed. LAP⁺CD4⁺ T cells have marked inhibitory effects, and in the peripheral blood and tumor tissues of patients with HCC, they have an important role in the suppression of anti-tumor immunity and in the immune evasion of tumor cells.

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