Fig. 4.

Perivascular loss of aquaporin 4-reactivity. A Localization and immunohistochemical characterization of leaky vessels allowing antibody entry into the CNS parenchyma. Shown here is the lesion load of individual animals, projected in red onto brain and spinal cord schemes provided by Paxinos and Watson [33] as guide lines (Aa, Ah, Am). The ends of the black arrows indicate the exact location of the vessels reacted in consecutive sections with anti-mouse IgG (Ab, Ai, An, brown), anti-complement C9neo (Ac, Ao, red), ED1 (Ad, Aj, Ap, brown), anti-AQP4 (Ae, Ak, Aq, brown), anti-GFAP (Af, Ar, brown), and anti-CD3 (Ag, Al, as, brown). In all sections, counterstaining was done with hematoxylin to reveal nuclei (blue). B Histological characterization of perivascular lesions found in the brain (Ba, Bc, Be) and spinal cord (Bb, Bd, Bf) of Lewis rats injected daily with the monoclonal AQP4-specific murine E5415A IgG and sacrificed after 120 h. Consecutive sections were stained with anti-AQP4 (Ba, Bb; brown), ED1 (Bc, Bd; brown), and anti-complement C9neo (Be, Bf; red). Counterstaining was done with hematoxylin to reveal nuclei (blue). C Demonstration of neutrophils in and of a near-complete absence of T cells from perivascular lesions. Consecutive lesions derived from spinal cord (Ca, Cb, Ce) and brain (Cc, Cd, Cf) of Lewis rats injected daily with the monoclonal AQP4-specific murine E5415A IgG and sacrificed after 120 h, and were reacted with antibodies against AQP4 (Ca, Cc, Cg, Ch) and against CD3 (Cb, Cd, Ce, Cf). The squares with dotted lines in Ca and Cc outline areas shown in higher magnification in Cg and Ch, respectively, to demonstrate the presence of neutrophils. The arrows in cb and cd point to CD3-positive T cells, and the squares with straight lines shown in Cb and Cd indicate lesion areas shown in higher magnification in Ce and Cf, respectively, to show single T cells