INTERLEUKIN-6 AND ERYTHROPOIETIN ACT AS DIRECT POTENTIATORS AND INDUCERS OF IN-VITRO CYTOPLASMIC PROCESS FORMATION ON PURIFIED MOUSE MEGAKARYOCYTES

Mouse megakaryocytes were purified using a rabbit antimouse platelet s erum, and magnetic beads were conjugated with an antirabbit IgG antibo dy. The purified cells were 95.8 +/- 1.2% megakaryocytes, and the reco very and viability of the megakaryocytes were 70 +/- 18.4% and 80 +/- 13.4%, respectively. The effects of recombinant erythropoietin (Epo), interleukin-6 (IL-6), and IL-1 beta on these purified megakaryocytes w ere studied. Epo and IL-6 significantly increased DNA synthesis in the se cells, but IL-1 beta did not. Similarly, both Epo and IL-6, but not IL-1 beta, increased the acetylcholinesterase (AchE) activity in the megakaryocytes. Epo and IL-6 stimulated the megakaryocytes to form cyt oplasmic processes, which are considered to represent in vitro proplat elet formation. This process formation was inhibited by the addition o f colchicine to the cultures. It was concluded that Epo and IL-6 are n ot only direct potentiators of megakaryocytes, but also inducers of in vitro cytoplasmic process formation on megakaryocytes.