B cell-mediated maintenance of CD169 cells is critical for liver regeneration.

The liver has an extraordinary capacity to regenerate through activation of key molecular pathways. However, central regulators controlling liver regeneration remain insufficiently studied. Here, we show that B cell-deficient animals failed to induce sufficient liver regeneration after partial hepatectomy (PHx). Consistently, adoptive transfer of B cells could rescue defective liver regeneration. B cell-mediated lymphotoxin beta production promoted recovery from PHx. Absence of B cells coincided with loss of splenic cluster of differentiation 169-positive (CD169(+)) macrophages. Moreover, depletion of CD169(+) cells resulted in defective liver regeneration and decreased survival, which was associated with reduced hepatocyte proliferation. Mechanistically, CD169(+) cells contributed to liver regeneration by inducing hepatic interleukin-6 (IL-6) production and signal transducer and activator of transcription 3 activation. Accordingly, treatment of CD169(+) cell-depleted animals with IL-6/IL-6 receptor rescued liver regeneration and severe pathology following PHx. Conclusion: We identified CD169(+) cells to be a central trigger for liver regeneration, by inducing key signaling pathways important for liver regeneration. (HEPATOLOGY 2018;68:2348-2361).