Ex vivo expansion of T, NK and CD34+ cells from umbilical cord blood.

Umbilical cord blood stem cell transplantation (CBSCT) has made significant progress in treatment of lethal congenital or malignant disorders. Both the incidence and severity of GVHD from CBSCT were lower than that from bone marrow and peripheral blood stem cell transplantation, particularly for adult patients, but these advantages were also associated with higher rates of relapse. The immune-mediated effect of natural killer and cytotoxic T cells against residual tumor cells were shown to prevent relapse and to induce remission after bone marrow transplantation. To explore possibility of ex vivo expansion of T, NK and CD34(+) cells from umbilical cord blood, cord blood was expanded ex vivo with different combinations of cytokines, T and NK cells proliferation and differentiation were observed. CB MNCs were separated in Ficoll-Isopaque column and cultured in IMDM for 14 days with different recombinant cytokines. Cultured cells were collected and analyzed for progenitor/stem cell immunophenotyping at day 0, 3, 7, and 14 by using flow cytometry. The results indicated that all test groups cultured with different combinations of SCF, IL-3, IL-6, IL-7, IL-2 showed significant expansion of UCB MNC, compared with the group without cytokines. All test groups showed expansion effects on CD34(+) cells, CD34(+) percentage went up from 1.6% in fresh CB to the highest 11.9% in group D (SCF + IL-3, IL-6, IL-2). The CD34(+) cells peak displayed at day 7 of culture in group A and D, while in other two groups B and C appeared at day 14 of culture. The expansion multiple of CD34(+) cells in all test groups at day 7 of culture were from 10 to 50. The average value of CD3(+) T cell in fresh UCB was 18.7 +/- 4.3%, the CD3(+) T cells decreased sharply in the medium without any interleukin, while obvious increase were observed in the other test groups containing different combinations of cytokines. The maximal expansion multiple of CD3(+) T cells reached 2 times of the fresh UCB level. CD56(+) cells amounted to 3.6 +/- 1.9% of fresh UCB, CD56(+) cell number increased significantly only in medium containing IL-2. It is concluded that T cells, NK cells as well as stem/progenitor cells can be expanded in the same time from CB-MNC with the combinations of cytokines.