Effect of granulocytic chalone on the growth rate of continuous cell lines propagated in vitro : a new assay system

The progress of research on granulocytic chalone has been hampered by a lack of reliable assay systems. This paper reports the use of continuous cell lines growing in liquid suspension culture as a new method for assessing the effect of granulocytic chalone on cell proliferation. Partially purified granulocytic chalone (PPGC) was added to cultures of a rat myeloid cell line (W25), a human myeloid cell line (HL60), a human B lymphocytic cell line (8392), and a human T lymphocytic cell line (8402). The growth rate of the target cell populations was directly assessed by serial cell counts. PPGC pretreatment resulted in a significant inhibition of cell proliferation of the 2 myeloid permanent cell lines, while the growth rate of the lymphocytic cell lines was not affected. Moreover, inhibition of cell proliferation was spontaneously reversed when PPGC treatment was discontinued. Since PPGC from ox leucocytes displayed an inhibitory effect on cell proliferation which was specific to the myeloid cells, spontaneously reversible and not species-specific, it appears to have all the essential properties of a granulocytic chalone.