Effects of cord blood transfer on the hematopoietic recovery following sublethal irradiation in MRL lpr/lpr mice.

The potential of cord blood (CB) to serve as a rich source of stem cells and stem cell factors is receiving increasing attention. In addition, perhaps because of the early ontogeny of these cells or the lack of surface antigens, cord blood stem cells do not appear to require close identity with the recipient. In the present pilot study, we investigated the presence of a hematopoiesis enhancing effect (HEE) by assaying the ability of human cord blood cells to augment hematopoiesis across a species barrier. For these experiments, autoimmune-prone MRL-Ipr/Ipr mice were exposed to sublethal levels of irradiation and cord blood administration to study the role of factors present in human cord blood in augmenting the rate of lymphopoiesis. This strain was chosen because of the increased presence of peripheral T and B subpopulations, namely the B-1 and CD4/CD8 double negative T-cell subpopulations, which do not arise directly from bone marrow precursors, but rather accumulate with age. MRL-Ipr/Ipr mice were sublethally irradiated and reconstituted with syngeneic bone marrow (BM) cells or with human cord blood cells or peripheral blood mononuclear cells (PBMC), or were left unreconstituted. At 2 weeks post-treatment, lymphoid populations in the spleen and lymph nodes were studied as a measure of hematopoiesis. Factors present in cord blood were able to augment hematopoiesis over that which occurred endogenously. At 2 weeks postirradiation, recipients of BM cells displayed the fastest rate of peripheral lymphoid recovery, nonreconstituted mice showed the slowest lymphoid recovery, and recipients of cord blood recovered their lymphoid populations at an intermediate rate. Similarly, myelopoiesis was increased in irradiated SJL/J recipients of human cord blood. Thus, human cord blood cells appear to produce/induce factors that may act as an adjunct to increase stem-cell activity.