Suppression of monocyte mediated anti U562 cytotoxicity by soluble factors in the serum of cancer patients and in the supernatant of K562 cell culture

Anti U562 cytotoxicity of monocytes isolated from blood of patients with alimentary tract cancer was shown to be depressed compared to monocytes of healthy individuals. A serum factor was demonstrated in the patients which depressed the cytotoxicity of healthy donor monocytes. Such suppressive factor was also produced by the K562 cell line and its production was blocked by indomethacin, a prostaglandin synthesis inhibitor, as well as by thymus preparations TFX and Thymex L.