Immunohistochemical study of flotillin-1 in the spinal cord of Lewis rats with experimental autoimmune encephalomyelitis.

We analyzed flotillin-1 expression in the spinal cords of Lewis rats with experimental autoimmune encephalomyelitis (EAE). Western blot analysis showed that flotillin-1 expression increased significantly in the spinal cords from rats at the peak stage of EAE compared with the levels in control animals (p<0.05) and declined thereafter. Immunohistochemistry demonstrated that flotillin-1 was expressed constitutively in the gray matter (particularly in the dorsal horn) of the normal rat spinal cord and in some neurons and glial cells. In EAE lesions, flotillin-1 immunoreactivity was detected in some macrophages and astrocytes, in which cathepsin D, a lysosomal marker, was localized. In the spinal cord cells in EAE, there was increased expression of flotillin-1 above the constitutive expression of flotillin-1 in normal spinal cords. Taking all these findings into consideration, we postulate that expression of flotillin-1 begins to increase when EAE is initiated and that flotillin-1 contributes to the formation of phagosomes in affected cells in EAE.