SELECTIVE ELIMINATION OF IMMUNOLOGICALLY COMPETENT CELLS FROM BONE MARROW AND LYMPHOCYTE CELL MIXTURES .3. IN VITRO TEST FOR DETECTION OF IMMUNOCOMPETENT CELLS IN FRACTIONATED MOUSE SPLEEN CELL SUSPENSIONS AND PRIMATE BONE MARROW SUSPENSIONS

Application of the density gradient centrifugation technique for fractionation of mouse spleen cell suspensions to primate bone marrow, as a method to separate the immunocompetent cells from the haemopoietic stem cells to be grafted, resulted in a moderate but still fatal secondary disease in the recipient. Therefore, minor changes of the separation technique for primate bone marrow were necessary. Since adequate microscopic identification of the two cell types to be separated is not possible, assays for their functional characteristics had to be developed. The impracticability of in vivo assays in primates necessitates an investigation of in vitro properties of the immunocompetent cell and haemopoietic stem cell. With regard to the immunocompetent cells, the phenomenon of transformation of lymphoid cells by phytohemagglutinin was used. The reliability of this in vitro test, called phytohemagglutinin-response test, was ascertained by quantitative comparison with the graft-versus-host assay in vivo in mice in different cell suspensions under a variety of conditions. With regard to the in vitro test for haemopoietic stem cells, a method is described which appeared to be not specifically indicative for stem cells but, nevertheless has been found to be of value as a check on the reproducibility of the separation technique. © 1969 by the Williams and Wilkins Co.