Neuraminidase treatment reduces NK cell cytotoxicity. (A) FACS analysis of PSA expression with and without Clostridium perfringens Neuraminidase treatment. (B) CD56+ cells with and without Neuraminidase treatment were investigated in a 4 h-killing assay. Data shown are the average mean ± SEM from one out of three independent experiments (C) Comparison of killing efficiencies at the target effector ratio 1:50 shows a significant reduction of cytotoxicity after Neuraminidase treatment. Data shown are the average mean ± SEM from three independent experiments (p = 0.0025). Control refers to the killing efficiency of untreated NK cells. (D) Comparison of vitality with and without neuraminidase treatment shows no significant difference. Data shown are the average mean ± SEM from three independent experiments.