Increased expression of cytotoxic and activation markers on macaque NK-cell subsets from SIV-infected animals. (A) Representative polychromatic flow cytometric overlay depicting coordinate but variable expression of intracellular granzyme B and perforin by all peripheral blood NK subsets. (B) Mean fluorescence intensities of granzyme B (top panel) and perforin (bottom panel) and (C) percentages of positive cells above background of cell-surface CD69 are shown for each of the NK subsets in naive and SIV-infected animals. Only significant P values are shown for naive versus SIV-infected comparisons. Mann-Whitney test; *P < .05; **P < .01; ***P < .001.