No significant differences in the expression of activating or inhibitory receptors on NK cells at baseline between asymptomatic and symptomatic individuals. Percentages of NK cells expressing (A) the activating receptors NKG2C or NKG2D, or (B), the inhibitory receptors NKG2A, KIR2DL1, KIR2DL2/L3/S2, or KIR3DL1. Percentages were calculated as the number of cells positive for the specified receptor out of the number of total NK cells (CD56+). No significant differences were observed between the asymptomatic (n = 42) vs. symptomatic (n = 46) groups for any of the receptors based on Mann Whitney U test.