Cytotoxic activity of human decidual natural killer cells against k562 cell line and its hla-g transfectant

Problem: Due to high abundance of decidual CD56+ NK cells in close contact with extravillous trophoblast cells, influence of HLA-G molecule on FasL-mediated cytotoxicity was investigated. Methods of study: Decidual mononuclear cells were isolated by density gradient and decidual lymphocytes were collected immediately or after overnight culture. Cytolytic activity of magnetically separated CD56+ cells against K562 and K562-HLA-G was analyzed by PKH-26 and flow cytometry. RT-PCR was performed to detect perforin and FasL mRNAs in decidual lymphocytes cultured overnight. Results: After overnight culture within decidual mononuclear cells, decidual NK cells express FasL mRNA and are able to induce FasL protein expression in close contact with HLA-G molecule. Freshly isolated or overnight cultured CD56+ cells similarly lyse K562 and K562-HLA-G cells. Both perforin and FasL are equally involved in the lysis of K562, while FasL represents a dominant mechanism of cytotoxicity for K562-HLA-G, although perforin is employed. Conclusions: HLA-G induces FasL protein in NK cells which significantly contributes to the lysis of K562-HLA-G targets, indicating the importance of Fas/FasL-mediated killing. Supported by the Ministry of Science, Republic of Croatia (Grant No. 0062029) and EMBIC project (No. 512040, LSHM-CT-2004-512040)