Factors that influence lymphocyte yields in lymphocytapheresis

The recent use of lymphocytapheresis to treat immune-mediated diseases such as rheumatoid arthritis prompted a study of factors that influence the cell composition of lymphocytapheresis concentrates. Following single cytapheresis procedures, using protocols recommended by manufacturers, lymphocyte yields were significantly higher with the model 2997 (IBM) and CS-3000 (Fenwal) cell separators as compared to the model 30 (Haemonetics) separator (9.8 +/- 1.1 and 7.1 +/- 1.2 X 10(9) lymphocytes, respectively, versus 4.6 +/- 1.1 X 10(9); p less than 0.01). The lymphocyte concentrate obtained with the CS-3000 separator contained the smallest number of monocytes (0.6 +/- 0.4 X 10(9) versus 1.4 +/- 1.6 and 1 +/- 0.3 X 10(9) for the model 2997 and 30 cell separators, respectively). Platelet contamination of the lymphocyte concentrate was highest with the CS-3000 (6.5 +/- 2.4 X 10(11], and erythrocyte contamination was highest when the model 30 was used (21 +/- 3.0%). Studies using the model 2997 indicated that lymphocyte yields were significantly influenced by donor pre-apheresis absolute lymphocyte counts, and for this cell separator by specific operating variables, such as channel centrifugation speed and positioning of the red cell interface during lymphocyte collection. Maximal yields were obtained when the channel centrifugation speed was 800 to 1000 rpm (equivalent to 100-150 X g) and the red cell interface was adjusted to yield a cell concentrate with a hematocrit less than 4 percent. These results suggest that it will be necessary to standardize lymphocytapheresis collection protocols in future studies to assess the role of lymphocytapheresis in the management of immune-mediated diseases such as rheumatoid arthritis.