Effect of apoA-I on the activity human purified PLTP. Panel A, PLTP isolated from human plasma was pre-incubated for 2 hours at room temperature in the presence of increasing concentrations of apoA-I and thereafter assayed for phospholipid transfer activity. As a control, 50 μg apoA-I were added to the reaction mixture in the absence of PLTP. A linear relationship between apoA-I concentration and PLTP activity was observed (R2 = 0.969). Dots and error bars represent mean ± SD calculated from triplicates. Panel B, apoA-I was pre-incubated with non-specific rabbit polyclonal antibodies (NS IgG) and anti-apoA-I rabbit polyclonal antibodies (R314) and the effects on PLTP activity were evaluated. Figures are representative for three independent experiments. Bars and error bars represent mean ± SD calculated from triplicates. **P < 0.01.