Panel I: Normal donor monitoring standards

In vitro study of immunologic changes in long-term cytapheresis donors

Several in vitro measurements of immune function were examined retrospectively in a population of active long-term cytapheresis donors (group I; n = 50) and the results were compared to age- and sex-matched controls (group II; n = 50) who had donated only whole blood. In group I, significantly different mean absolute lymphocyte counts (P = .0025), total T-cells (P = .0026) and T-helper cells (P less than .0001), and helper-to-suppressor ratios (P = .0279) were present. No differences were noted between the two groups for peripheral blood mean B-cell count, T-suppressor numbers, lymphocyte responsiveness to mitogens or alloantigen, and serum immunoglobulin level. The reduced mean absolute lymphocyte count in group I was due to the reduction in T-helper cell numbers and accounted for the imbalance in the helper-to-suppressor ratio. These disturbances are currently unexplained and, while no clinical consequences have so far become evident, there is a need to continuously monitor the immunologic status of cytapheresis donors. It is also important to determine whether reversal of the defects occurs and, if so, over what time interval.

The effect of acute and chronic leukapheresis on the natural killer (NK) cell function of normal human volunteers

Twenty-two normal volunteers had approximately eight, 2-hr-long leukapheresis procedures over a 2-year period and their natural killer (NK) cell function was prospectively measured. The NK activity of the preprocedure peripheral blood (pre-PB) was found to correlate well with the NK activity of the inital leukocytes removed by leukapheresis (I-Leuk). When the I-Leuk specimens were compared with the leukapheresis specimens removed at the termination of leukapheresis (T-Leuk), T-Leuk showed a consistent 10% increase in NK activity. When the pre-PB and the I-Leuk values were analyzed for each donor over the 2 years of the study, 18 donors revealed no significant change from their baseline NK activity, two donors showed a minimal increase in NK cell activity, and two donors displayed a minimal decrease in NK cell activity. We conclude that although leukapheresis appears acutely to boost NK cell activity, this increase is transient and small in magnitude. Most importantly, repeated leukapheresis does not appear adversely to effect this important effector function in normal donors.