Yoshifumi Kawano

Combination of recombinant cytokines fails to produce ex vivo expansion of human blood hematopoietic progenitor cells.

SummaryThe concept of ex vivo expansion of the human progenitor cell population was tested in this study. In the presence of interleukin-3 and -6 we compared the abilities of various liquid culture conditions of human blood-derived hematopoietic progenitor cells to yield a suitable condition for the expansion of blood progenitor cells. Although the best result was obtained in the gas-permeable bag culture system, the enhancement effect (maximum of 3.8-fold for granulocyte/macrophage colony-forming units and 3.0-fold for erythroid burst-forming units) lasted for only a short period (< 6 d). The results of this study are disappointing for clinical use, and attempts with currently available technology appear to be limited in their potential.

A simplified and rapid limiting dilution assay of T lymphocytes

We report here the development of an alternative limiting dilution assay (LDA) of T lymphocytes (T cells). Blood mononuclear cells were first stimulated for 60 hr with PHA and then cultured in microwells in the presence of recombinant interleukin-2 without feeder cells. After 4 days of culture, wells were scored for proliferation. Clonal expansion of T cells followed the single-hit model of the Poisson distribution. The progenitor frequency (f) in the mononuclear cells and E-rosette-positive cells from normal donors were 0.082 +/- 0.025 (n = 12) and 0.236 +/- 0.029 (n = 5), respectively, but this was markedly decreased in patients who underwent marrow-ablative chemotherapy and autografts with blood hematopoietic stem cells. This LDA system should be of value in routine use for the evaluation of T cell proliferative activities.