Introduction of macromolecules into hemopoietic stem cells with an erythrocyte-ghost-mediated system

We have developed a method of introduction of macromolecules into normal human hemopoietic stem cells. The erythrocyte ghosts were loaded with diphtheria toxin fragment A (molecular weight = 22,000 daltons), which exerts cytotoxicity only in the intracellular space. Granulocyte-macrophage colonies of human bone marrow cells incubated with the above ghosts in the presence of Sendai virus decreased in number to about 10% of the control. This means that the cell fusion and the subsequent introduction of the fragment A into granulocyte-macrophage progenitors occurred at a high incidence (about 90%). This method will be useful to study intracellular events during the proliferation and differentiation of hemopoietic stem cells.