Non-adherent peripheral blood mononuclear cells (PBMC) from 15 patients with carcinoma of the stomach and 6 normal healthy controls were assessed for natural killer cell mediated cytotoxicity (NKCMC) and antibody dependent cellular cytotoxicity (ADCC) in a 4 hour (51)Chromium release assay against target cells, K-562 and sensitized chicken red blood cells (CRBC), respectively. NKCMC and ADCC were significantly reduced in patients with respect to normal controls. However, significant enhancement in NKCMC and ADCC was observed when PBMC from patients were cultured in RPMI-1640 containing 200 IU/ml of Interleukin-2 (IL-2) for 4 days in 5% CO2 atmosphere at 37 degrees C. Augmentation of NKCMC and ADCC was also detected when a follow-up study of the patients was conducted after one month following initial trial of chemotherapy with 5-fluorouracil (5-Fu). Patients, who had undergone clinical trial with 5-Fu were better responders of IL-2 activation as reflected on NK cell and ADCC potential of these patients. Our investigations highlight the synergistic effect of 5-Fu and IL-2 on effecters of natural immunity in patients with carcinoma of the stomach, Judicious modulation of effecters may be beneficial in killing residual cancer cells in vivo.

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