[Immunomodulatory effect of serum on NK cells in vitro in healthy individuals]

The regulatory role of the immune system in malignancies is realized through cytotoxic cells. The main cytotoxic cells that destroy tumor cells are NK cells. Considering this, the activity and regulation of NK cell function is of significance in malignant diseases. Our previous studies showed that different sera had a profound effect on the NK activity of breast cancer patients. In this work we tried to investigate these effects on the NK cell activity of healthy individuals. Our data indicate that the FCS has a profound stimulative effect on the activity of NK cells of healthy donors. We also found that healthy control serum induces a significant inhibition of NK cell activity of these donors. Compared to this effect of healthy sera, sera of breast cancer patients with early clinical stage I-III induced a significant activation of NK cell activity while sera of patients with advanced breast cancer, stage IV with generalized metastases, gave a significant decrease of the NK cell activity of healthy individuals. In this study several sera of patients with stage IV of the disease without metastases gave the greatest inhibition of the NK cell activity which were not found in our previous more extensive investigations of this type of sera. We confirmed that the investigated sera displayed the same effects on the activity of NK cells of healthy persons as they did on NK cells of breast cancer patients. These findings not only indicate the cause of the impaired NK cell activity in patients with malignant disease but also give an indication for immunotherapeutic approaches.