1. A method for assessing changes in cardiovascular homeostasis, comprising: a. obtaining a biological specimen from a test subject suspected of having a cardiovascular disorder, a biological specimen comprising a mixed cell population suspected having target cells from the group consisting of endothelial cells, subpopulations of endothelial cells, epithelial cells, and combinations thereof; b. contacting said biolgical specimen with a preservative capable of stabilizing said mixed population; c. mixing said biological specimen with colloidal magnetic particles coupled to a monoclonal antibody which binds specifically to said target cells, to the substantial exclusion of other specimen components; d. subjecting the specimen-magnetic particle mixture to a high gradient magnetic field to produce a separated cell fraction enriched in magnetic particle-bound target cells; and e. analyzing said enriched fraction for the presence of target cells, the presence of said target cells is indicative of an change in homeostasis.