C3 Synthesis and CRs Expression during DiHerentiation of a Murine Stem Cell Line

Abstract C3 production, release and CRs expression during the neutrophilic differentiation of a murine non tumorigenic cell line is investigated. The murine non tumorigenic cell line 32DC13(G) which undergoes terminal differentiation into polymorphonuclear granulocytes when cultured in presence of G-CSF was selected as a suitable in vitro model for this study. The results show that as the cells progress into the differentiation program, levels of C3 mRNA increase, accompanied by increased C3 production. As differentiation progresses the cells gradually express CRs on their surface; these are undetectable on the surface of undifferentiated cells. As a consequence of CRs appearance, cells become able to bind C3 through receptorial binding. Differences were found in the modality of C3 secretion: differentiated cells tend to store C3 in their intracellular compartments rather than secrete it continuously into the medium and they respond to membrane stimulation with increased secretion of C3. Treatment of 32DC13(G) with TNF-a increased C3 production in a time- and dose-dependent fashion. Cell response to this stimulus progressively increases during the differentiation process suggesting that they acquire functionality in the signal transduction mechanisms.