Peripheral blood lymphocyte trends in naive volunteers undergoing frequent plateletpheresis. Ten healthy male volunteers donated apheresis platelets 10 times in 12 weeks on the Haemonetics Model 30 blood processor. Blood samples were obtained at baseline and at each of the plateletpheresis procedures. The plotted points show, for each volunteer, the percentage change in total peripheral blood lymphocytes relative to that volunteer's mean lymphocyte count for the entire study period. The solid regression line shows the average change for all participants; ±2 SD confidence intervals are indicated by the dashed lines.