Objective: To investigate the immune tolerance inducing effects of soluble human leucocyte antigen G1 (sHLA-G1) on natural killer (NK) cells and T cells.
Methods: A recombinant plasmid expressing sHLA-G1 was constructed and transfected into human lymphoblastoid cells LCL721.221. sHLA-G1 in the supernatant was purified by immuno-affinity chromatography and then added into the culture of NK cells obtained from the peripheral blood mononuclear cells of 3 unrelated individuals. Target cells, K562 cells, were added too. The killing rate of NK was calculated. Peripheral blood lymphocytes (PBLs) were obtained and stimulated by Ebstein-Barr-virus-transformed B lymphoblastoid cell line (EBV-LCL). The proliferation of the T cells in the mixed lymphocyte culture was examined by enzyme linked immunosorbent assay. The antigen-specific T cells in the peripheral blood was activated. sHLA-G1 was added into the culture. Then the T cells were suspended in the solution of fluorescence isothiocyanate (FITC)-annexin-V. Flow cytometry was used to detect the fluorescent intensity of FITC so as to examine the apoptosis of T cells.
Results: sHLAG-1 inhibited the cytotoxicity of NK cells dose-dependently. sHLAG-1 inhibited the proliferation of activated T cells, and induced the apoptosis of T cells dose-dependently, with a dose-saturation character and without antigen-specificity.
Conclusion: sHLAG-1 is a kind of immune tolerance inducing molecule.