SUPPRESSIVE INTERACTION OF BREAST-CANCER PATIENTS SERA ON INTERLEUKIN-2 INDUCED STIMULATION OF NATURAL-KILLER-CELLS

As NK cells have a main role in controlling the appearance and spreadi ng of malignancies, as well as in the success of LAK therapy, the acti vity of NK cells in breast cancer patients was investigated and an imp airment was found in all clinical stages. Pretreatment with IL-2 great ly enhanced this activity. In vitro study of the effect of sera of 33 breast cancer patients in clinical stage IV of disease with metastases on NK cell activity of healthy controls showed that all sera had an i nhibitory effect, the average obtained inhibition being 44% compared t o control sera, while in one third it was over 60%. In in vitro condit ions these pooled sera also interfered with the activating effect of I L-2, while removal of the sera prior to IL-2 treatment gave optimal ac tivation of NK cells. The inhibitory effect of sera is not induced by molecules of low molecular weight. The greatest inhibition was found w ith dialyzed sera which excludes substances below 10,000 D, such as pr ostaglandins. Moreover, molecules of greater molecular weight, includi ng soluble IL-2 receptors, could be responsible for this effect, as in our group of investigated sera the average level of these molecules w as increased. The obtained data indicate the need for determining the presence of different factors in an individual patient which could int erfere with the successful application of IL-2 and LAK cells to cancer patients with the hope of improving clinical response rate.