FN1 and lupus nephritis: Interaction of nephritogenic human polyclonal anti-dsDNA antibodies with cultured human or rat mesangial cells induced cell proliferation, apoptosis, PKC activation, secretion of IL-6, IL-1β, TNF-α, TGF-β1, and hyaluronan, and fibronectin synthesis (37, 55, 56, 78, 79), suggesting that anti-dsDNA antibodies may contribute to mesangial expansion, hypercellularity, increased apoptosis, inflammation, and fibrogenesis observed in lupus nephritis.