Influence of Platelet Depletion on Immunomagnetic CD34+ Cell Selection for Haploidentical Transplants.

Introduction: Immunomagnetic CD34+ cell selection (ICS) is a widely employed technology in auto and allotransplant settings. In particular, when an haploidentical transplant is performed an high dose of purified CD34+ cells together with an efficient T and B cells depletion are requested to minimize the risks of GVHD and EBV related lymphoma. In order to ameliorate the performances of the ICS device, we compared 73 ICS performed following the customer’s recommendations vs 20 ICS performed after 3 centrifugations in order to increase the platelet depletion of the starting leukapheresis (LKF) product.

Matherials and Methods: 93 ICS (from single or fractioned LKF product) were carried out using the Miltenyi Clinimacs device on 76 LKF collected from 37 healty donors mobilized with G-CSF alone (12μg/kg). In tab 1 are summarized the characteristics of the starting 93 pre-immunoselection products in terms of TNC, CD34+ cells, plt and T and B lymphocyte content. 73 LKF were prepared following the standard manufacturer’s protocol and the remaining 20 with an adjunctive plt depletion obtained by 3 low speed centrifugations (900 rpm).

Results: a statistical significance in terms of CD34+ cells recovery, final TNC (x10⁶) and CD34+ cell (x10⁶) absolute count was found in favour of the modified immunoselection procedure (see tab.1).

Conclusions: ICS demonstrated to be an highly efficient procedure when the Miltenyi Clinimacs device is employed. Moreover, the modification of the standard manufacturer’s technique simply by adjunctive centrifugations on the starting LKF product can further improve the recovery of stem cells maintaining, at the same time, a good purity and not influencing the T and B cells log of depletion, thus demonstrating the negative influence of plt contamination on ICS. These results are more remarkable in the context of haploidentical transplant where the plt contamination of LKF is particularly high. Table 1