Defective natural killer activity in gastric cancer patients: possible involvement of suppressor factor receptor.

The mechanism of defective natural killer (NK) activity in gastric cancer patients was studied with respect to the soluble immune suppressor factor receptor on NK cells. Phycoerythrin (PE)-conjugated anti-CD8 and -CD16 antibodies were used for the determination of NK phenotype, and fluorescein isothiocyanate (FITC)-conjugated wheat germ agglutinin (WGA) was for the lymphocyte surface receptor of soluble immune suppressor factor (SISF). It was found that NK activity of peripheral blood lymphocytes (PBLs) isolated from gactric cancer patients decreased with tumor progression in spite of an increasing tendency of their CD16+ population. The WGA+ population of PBLs inversely increased in parallel with cancer progression and a significant negative correlation was found between NK activity and the WGA+ population. Two-color flow cytometry showed a significant increase of WGA+ cells in the CD8dim and CD16+ population in advanced cancer patients. It is suggested that an increase of surface receptors for SISF on NK cells may, in part, cause the diminished NK activity in gastric cancer patients.