Comparison of the number of spheroids in T44, T44;NFL+/−, and T44;NFL−/− Tg mice. The sections were stained with 17026, a polyclonal antibody to recombinant tau protein. Note the reduction in the number of tau-positive spheroids in the bigenic mice relative to the T44 mice at 6 months of age. All photomicrographs are at the same magnification. Scale bar, 10 μm.