Immunomagnetic cell selection performed for HLA haploidentical transplants with the CliniMACS device: effect of additional platelet removal on CD34+ cell recovery.

Immunomagnetic CD34+ cell selection (ICS) is a widely employed technology in autotransplant and allotransplant settings. When an haploidentical transplant is performed, a high dose of purified CD34+ cells together with efficient T and B cell depletion are required to minimize the risks of graft versus host disease (GVHD) and Epstein-Barr virus (EBV)-related lymphoma. To ameliorate the performances of the CliniMACS (Miltenyi Biotec) ICS device, we compared 73 ICS performed following the manufacturer's recommended platelet depletion versus 48 performed after adjunctive centrifugations to increase platelet depletion of the leukapheresis (LKF) product. A total of 121 ICS (from single or fractioned LKF products) were carried out on 93 LKF collected from 47 related healthy donors. A statistical significance in terms of CD34+ cell recovery (81.8% vs. 71.2%) was found in favor of the modified ICS procedure (p=0.0049) with a comparable stem cell purity and viability. The modification of the standard manufacturer's technique for increasing platelet depletion can further improve the recovery of stem cells with no influence on T and B cell depletion. These results demonstrate the negative influence exerted on CD34+ cell recovery by LKF platelet contamination.