PECAM1 and myeloid sarcoma: The results of the present study, together with the findings of other investigators, suggest that IFN-β1a, through its stabilizing effects on the cerebral endothelial cells, decreases the number of released CD31+EMP and the pre- and post-treatment plasma levels of CD31+EMP, and that these levels may serve as a surrogate measure of disease activity in MS and patients' response to therapy.