- Complement factor 5 is a quantitative trait gene that modifies liver fibrogenesis in mice and humans. Hillebrandt, S., Wasmuth, H.E., Weiskirchen, R., Hellerbrand, C., Keppeler, H., Werth, A., Schirin-Sokhan, R., Wilkens, G., Geier, A., Lorenzen, J., Köhl, J., Gressner, A.M., Matern, S., Lammert, F. Nat. Genet. (2005)