Umbilical cord blood as a source of CD34 positive haematopoietic stem cells.

In this paper we have used a monoclonal antibody to CD34 an antigen expressed solely on stem cells, and stem cell colony assays to show that umbilical cord blood has nearly the same number of functional stem cells as compared to normal bone-marrow. The number of CD34+ve cells in cord blood being 2 to 2.7 per cent, whereas bone-marrow had 3 to 3.5 per cent. The multi-potent colony forming cells (CFU-GEMM) were 60 +/- 18 in cord blood per 2 x 10(5) mononuclear cells (MNCs), whereas normal bone-marrow had 70 +/- 10 per 2 x 10(5) MNCs. Enrichment of these stem cells on Percoll gradients was successful for normal bone-marrow but not for cord blood.

Enhancement of haemopoietic stem cell adherence to bone-marrow derived stroma by phyto-haemagglutinin treated leucocyte conditioned medium (PHA-LCM).

Stem cell adhesion to bone-marrow derived stroma, plays a crucial role in haemopoiesis. However, there is very little information as to the nature of the adhesion molecule. In this paper we have shown that human bone-marrow derived stroma can be established in tissue culture. This stroma is able to adhere human bone-marrow mononuclear cells including the multipotent stem cell, viz. CFU-GEMM. Their adherence increases when the stroma is treated with lymphokines in the form of PHA-treated leucocyte conditioned medium (PHA-LCM). Triton X-100 extracts of the untreated and PHA-LCM treated stroma were analysed on single dimension PAGE. It was observed that PHA-LCM treated stromal extracts showed two extra bands and an increase in the density of a band of approximately 14 kDa. Whether these changes have anything to do with the increased adhesion of stem cell is not yet known.