A total of 33 leukaphereses were performed with the IBM continuous flow centrifuge on 28 normal healthy donors for the purpose of obtaining increased yields of granulocytes for infusion into leukopenic recipients. The pretreatment of donors within a 10- to 12-hour period prior to pheresis with a double dose of dexamethasone and the addition of hydroxyethyl starch to the input line of the continuous flow centrifuge, significantly increased the total quantity and efficiency of granulocyte collected as compared to a donor group receiving a single dose of dexamethasone in addition to hydroxyethyl starch. A mean of 25.5 x 10^9 total granulocytes were collected in addition to an efficiency of 2.11 x 10^9 granulocytes harvested per liter of blood processed in the doubledose- treated donors, in contrast to 19.6 x 10^9 total granulocytes collected and an efficiency of 1.82 x 10^9 granulocytes harvested per liter of blood processed in the single dose donor group. The results of the present study demonstrate that elevated quantities of granulocytes can be collected from normal donors by scheduling a double dose of dexamethasone prior to the pheresis procedure.

The results of 38 HL-A and other antigen matching studies revealed an inverse relationship between the percent of donor-recipient serologic discordance and increases in recipient granulocyte levels 1 h after infusion of donor cells. Selected unrelated, parent, and sibling donors possessing mean percent serologic discordances of 33, 22, and 16, respectively, increased postinfusion granulocyte counts by 10, 46, and 117%, respectively. A mean of 1.58 x 10^10 total granulocytes collected from sibling donors was associated with a significant elevation of recipient levels, as compared to unfavorable results with the infusion of 2.05 x 10^10 and 2.31 x 10^10 total granulocytes harvested from less compatible parent and selected unrelated donors, respectively.