Re-programming of Kupffer Cells for immune regulation in response to ConA-induced liver injury

Introduction: In the mouse model of concanavalin A (ConA) induced hepatitis Kupffer cells (KCs) secrete large amounts of hepato-destructive TNFα. Sublethal doses of ConA induce tolerance towards ConA hepatitis in mice within less than two weeks and KCs secrete large amounts of IL–10 upon a second ConA dose. This study is intended to characterize the phenotype of Kupffer cells in ConA tolerant mice. Methods: Liver mononuclear cells were isolated via gradient centrifugation from tolerant mice 14 days after ConA administration or from control mice 14 days after saline administration. KCs were stained with F4/80 and analyzed for CD68 and CD11b expression via FACS analysis. Moreover, KCs were enriched via F4/80+ MACS sorting and in vitro restimulated with LPS. TNFα and IL–10 secretion from KCs into cell culture supernatants was quantified by ELISA. Functional re-programming of liver resident KC during first ConA inflammation was tested in an in vivo approach by depleting KCs one day before first ConA treatment. After 14 days mice were restimulated with ConA and ALT activities were determined 8 hours afterwards. Results: According to data from Kinoshita et al (J Hepatol., 2010) phagocytotic KCs express CD68 whereas cytokine secreting KCs express CD11b. The relative frequencies of these populations stay stable after ConA treatment. KCs from ConA tolerant and control mice secreted similar amounts of TNFα and IL–10 upon LPS in vitro stimulation. Furthermore, in vivo, tolerance was also observed in mice that were lacking KCs during the first ConA stimulation. Conclusion: Until now, our data do not provide any proof for a re-programming of KCs during first ConA stimulation. However, a potential switch from a proinflammatory M1 macrophage phenotype to an anti-inflammatory M2 macrophage phenotype of Kupffer cells will be analyzed.