FIG 1 . Cytolytic activity of natural killer cells in an elderly population
(n = 77). LU, bytic units: the number of cells required to cause
lysis of2O% of target cells per 106 peripheral blood lymphocytes (PBL),
calculated by a simple exponential fit equation from three ratios of
effector to target cells. Median, 8.8; i, 18.2: CV, 126%.