Enrichment of bone marrow and blood progenitor (CD34+) cells by density gradients with sufficient yields for transplantation.

We have evaluated the use of iso-osmolar Percoll density gradients to enrich CD34+ hematopoietic progenitor cells and to reduce T cells for purposes of bone marrow or mobilized peripheral blood cell transplantation (BMT or PBCT). Samples from 12 normal BM donors and 11 patients undergoing mobilization of PB cells using chemotherapy and G-CSF were placed over a five-step density gradient from 40 to 50% Percoll. In BM, low-density fractions 1 to 3 (40 to 45% Percoll) accounted for 3% of starting nucleated cells with a 10- to 20-fold enrichment of hematopoietic progenitors (CD34+ cells) and a 20-fold reduction of CD4+ and CD8+ T cells. In PB, fractions 1 to 3 accounted for 20 to 30% of the starting nucleated cells with a five-fold enrichment of hematopoietic progenitors. Based on these values, such populations have been used for clinical transplantation using a single apheresis. The reduced cell numbers in the low-density fractions can facilitate tumor purging, and the reduced T cell numbers present in the marrow may ameliorate graft-vs.-host disease.