Separation of tumor cells by density gradient centrifugation: recent work with human tumors and a discussion of the kind of quantitation needed in cell separation experiments.

The application of centrifugation to the purification of individual kinds of cells from tumors has been reviewed. Recent applications of a previously described isokinetic gradient to the purification of subpopulations of cells from human tumors are presented. Individual kinds of cells have been separated from Hodgkin's disease by a method described previously, and the cells from Hodgkin's disease which contain the tumor associated antigen described by Order and his colleagues have been identified for the first time. The importance of the thorough documentation of cell separation procedures is discussed, and we have specifically listed several kinds of data which we believe are important in the documentation of cell separation techniques.