Inhibitors of Haemopoietic Cell Proliferation?: Specificity of Action Within the Haemopoietic System

The specificity of action of mature blood cell extracts on their own progenitor cells was investigated by measuring their effects on the structuredness of the cytoplasmic matrix (SCM) using the technique of fluorescence polarization. Changes in SCM induced by the various extracts are probably closely related to the proliferation state of the cells. Saline extracts of lymphocytes, granulocytes and erythrocytes (LNE, GCE and RCE respectively) have been partially purified by ultrafiltration into selected molecular weight ranges and each tested against proliferative populations of lymphoid, granulocytic and erythroid cells. In all cases, complete specificity of effect on SCM was found, LNEs affecting only lymphoid cell populations, GCEs affecting only the granulocytic cell populations and RCEs affecting only erythroid cells. In each case, with the possible exception of the RCEs, the active fractions reside in the molecular weight ranges reported in the literature for cell extracts possessing proliferation inhibitory properties.