Abstract: Objective: To explore the function of tumor derived IgG (tIgG) and whether the tIgG can inhibit T cells activity. Methods: The tIgG was purified from ovarian cancer tissue. The cord blood monocyte cells (CBMC) and cord blood lymphocyte (CBL) were isolate from human umbilical cord blood. The CBMC and CBL were stimulated with phytohaemagg lutinin (PHA) in order to let the CBMC and CBL in the state of proliferation. Carboxyfluorescein succinimidyl amino ester (CFSE) was cultured with CBMC and CBL. CFSE had no cell toxicity, which could penetrate through the cell membrane and combine the intracellular protein. The fluorescence intensity decreased with the proliferation of cells step by step, so the proliferation of these cells could be detected in flow ctytometry. The tIgG which was purified from ovarian cancer tissue was divided into three groups, 1 mg/L group, 10 mg/L group, and 100 mg/L group, and the intravenous immunoglobulin (IVIG) was also divided into three groups too. The CBMC and CBL were treated by tIgG with 1 mg/L, 10 mg/L, and 100 mg/L in order to observe the proliferation of T cells. The cells were treated with IVIG as a positive control group, and the cells were treated with phosphate buffer saline (PBS) as a negative control. The proliferation of CD4⁺ or CD8⁺ T cells were detected in CBMC and CBL. The proliferation of the T cells in CBMC and CBL after 64 h and 86 h were detected. Results: In the system of CBMC, the tIgG could suppress the proliferation of CD4⁺ or CD8⁺ T cells. The results could also be found in the system of CBL. The CD4⁺ or CD8⁺ T cells in the group which were treated with PBS were more active than those in the group which were treated with tIgG and IVIG. The suppression in the group which were treated with tIgG, was stronger than that in the group treated with IVIG. In addition, the suppression of T cells in the group which were stimulated with tIgG as 100 mg/L was more effective than that in the group which were stimulated with tIgG as 10 mg/L. This could prove that tIgG had the function of immunomodulation. Conclusion: The tIgG can be involved in immune escape of cancer.

Key words: Immunoglobulin G, Immune escape, tumor, T-lymphocytes