The present invention provides human CD34-negative progenitor cells for the use in protecting the vascular endothelium from immunologically mediated cytotoxic reactions of a subject at risk of, or afflicted with, vascular inflammatory disease. Also provided are a method for producing the human CD34-negative progenitor cells and a method for determining the ability of CD34-negative progenitor cells to protect the vascular endothelium from immunologically mediated cytotoxic reactions.
