Correlation of immunolabeled LM and EM images of pretangles in a severe case of CBD. In a pretangle neuron from a severe case of CBD (case 4), reticular tau immunoreactivity was denser on 3D reconstruction (A). When focusing on the denser area of round inclusion (B, C), the corresponding EM section contained abundant tau-positive straight filaments that did not form a parallel arrangement (D). These straight filaments were thicker with a diameter of 15–20 nm (E). Scale bars in A-C = 10 μm; D = 500 nm; E = 100 nm.