A magnetic colloid system for isolation of rare cells from blood for FISH analysis

To improve cell recovery of trophoblast and nucleated red blood cells from maternal blood for diagnosis of chromosomal abnormalities, we have investigated the use of a magnetic sorting system that utilizes a ferrofluid. The main advantage of this system is that the beads used are small enough to allow visualization of chromosome‐specific sequences by fluorescence in situ hybridization (FISH). The ferrofluid was validated using MAb340, a trophoblast‐specific antibody, and anti‐CD71, used to sort for nucleated red blood cells. Antigen‐positive cells could be efficiently sorted from a 1000‐fold excess of antigen‐negative cells and easily stained by FISH. We are currently evaluating its use on maternal blood samples. © 1997 John Wiley & Sons, Ltd.