Improved immunomagnetic enrichment of CD34(+) cells from umbilical cord blood using the CliniMACS cell separation system

Background aimsCD34+ enrichment from cord blood units (CBU) is used increasingly in clinical applications involving ex vivo expansion. The CliniMACS instrument from Miltenyi Biotec is a current good manufacturing practice (cGMP) immunomagnetic selection system primarily designed for processing larger numbers of cells: a standard tubing set (TS) can process a maximum of 60 billion cells, while the larger capacity tubing set (LS) will handle 120 billion cells. In comparison, most CBU contain only 1–2 billion cells, raising a question regarding the optimal tubing set for CBU CD34+ enrichment. We compared CD34+ cell recovery and overall viability after CliniMACS processing of fresh CBU with either TS or LS.MethodsForty-six freshly collected CBU (≤ 36 h) were processed for CD34+ enrichment; 22 consecutive units were selected using TS and a subsequent 24 processed with LS. Cell counts and immunophenotyping were performed pre- and post-selection to assess total nucleated cells (TNC), viability and CD34+ cell content.ResultsTwo-sample t-tests of mean CD34+ recovery and viability revealed significant differences in favor of LS (CD34+ recovery, LS = 56%, TS = 45%, P = 0.003; viability, LS = 74%, TS = 59%, P = 0.011). Stepwise linear regression, considering pre-processing unit age, viability, TNC and CD34+ purity, demonstrated statistically significant correlations only with the tubing set used and age of unit.ConclusionsFor CD34+ enrichment from fresh CBU, LS provided higher post-selection viability and more efficient recovery. In this case, a lower maximum TNC specification of TS was not predictive of better performance. The same may hold for smaller scale enrichment of other cell types with the CliniMACS instrument.