THE USE OF COUNTERFLOW CENTRIFUGAL ELUTRIATION FOR THE DEPLETION OF T-CELLS FROM UNRELATED DONOR BONE-MARROW

Transplantation of marrow from unrelated donors is associated with an increased incidence and severity of graft-versus-host disease (GVHD). In an attempt to minimize GVHD without compromising engraftment, unrel ated donor marrow was depleted of lymphocytes by counterflow centrifug al elutriation (CCE), and a fixed dose of 0.5 x 10(6) CD3+ T cells/kg, as measured in real time by flow cytometry, was added back to the gra ft. Patients received cyclosporine (CYA) and corticosteroids for GVHD prophylaxis and to facilitate engraftment. In the first cohort (study I), 7 patients received busulfan (16 mg/kg) and cyclophosphamide (120 mg/kg) (CY) and one patient received CY (200 mg/kg) + 1260 cGy fractio nated TBI. Of 6 who were evaluable for both engraftment and rejection, 4 rejected their graft. The study was terminated, and the protocol wa s modified (study H) by the addition of antithymocyte globulin (ATG) t o the pre-BMT and post-BMT therapy. Twelve patients received CY + TBI as above plus ATG given pre-BMT and post-BMT. Ten of twelve who receiv ed ATG engrafted. Twelve patients from studies I and II were evaluable for acute GVHD. Two developed grade I acute GVHD. Two patients develo ped grade II acute GVHD, 2 patients developed grade III GVHD, and 1 pa tient developed grade IV acute GVHD. Two of three cases of acute GVHD (> grade II) occurred later than day 100 after BMT concomitant with re duction of immunosuppressive therapy. The rate of engraftment was sign ificantly higher in study II (p = .054). In numbers of CD34+ cells inf used, numbers of CFU-GM infused, and numbers of nucleated cells infuse d did not correlate with engraftment. We conclude that (a) in contrast to the results seen in recipients of marrow from HLA-matched sibling donors, the depletion of unrelated donor marrow of all but 0.5 x 10(6) CD34+ cells/kg together with CYA + corticosteroids was not sufficient to facilitate engraftment. The use of a more immunosuppressive regime n containing TBI and ATG appeared to improve engraftment. (b) The redu ction of the graft T cell dose to 0.5 x 10(6) CD34+ cells/kg resulted in a higher incidence of acute GVHD than that seen in recipients of ma rrow from genotypically identical donors whose marrow was similarly pr ocessed.