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 an d stem cell factors is receiving increasing attention. In addition, perhaps because of the early ontogeny of these cells or the lack of surface antige ns, 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 he matopoiesis enhancing effect (HEE) by assaying the ability of human cord bl ood cells to augment hematopoiesis across a species barrier. For these expe riments, autoimmune-prone MRL-lpr/lpr 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 s train was chosen because of the increased presence of peripheral T and B su bpopulations, namely the B-l and CD4/CD8 double negative T-cell subpopulati ons, which do not arise directly from bone marrow precursors, but rather ac cumulate with age. MRL-lpr/ lpr mice were sublethally irradiated and recons tituted with syngeneic bone marrow (BM) cells or with human cord blood cell s or peripheral blood mononuclear cells (PBMC), or were left unreconstitute d, At 2 weeks post-treatment, lymphoid populations in the spleen and lymph nodes were studied as a measure of hematopoiesis, Factors present in cord b lood were able to augment hematopoiesis over that which occurred endogenous ly, At 2 weeks postirradiation, recipients of BM cells displayed the fastes t rate of peripheral lymphoid recovery, nonreconstituted mice showed the sl owest lymphoid recovery, and recipients of cord blood recovered their lymph oid populations at an intermediate rate. Similarly, myelopoiesis was increa sed in irradiated SJL/J recipients of human cord blood, Thus, human cord bl ood cells appear to produce/induce factors that may act as an adjunct to in crease stem-cell activity.