Involvement of Fas/Fas ligand system in the spinal cords of HTLV-I-associated myelopathy.
To investigate whether the Fas/Fas ligand (FasL) system is involved in the pathogenesis of HTLV-I associated myelopathy (HAM), expression of Fas/FasL in the spinal cord lesions of HAM patients was examined by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR). Fas was preferentially expressed on infiltrating T cells in active-chronic lesions of HAM. FasL expression was up-regulated on various cells, mainly microglia/macrophages in active-chronic lesions. In contrast, Fas expression was markedly down-regulated in inactive-chronic lesions of HAM patients who had a long duration of illness. The expressions of Fas/FasL in inactive-chronic lesions were comparable to those of normal controls. In normal controls, vascular endothelial cells constitutively displayed both Fas and FasL immunoreactivity, while microglia expressed FasL. RT-PCR confirmed constitutive expression of both Fas mRNA and FasL mRNA in the spinal cords of HAM patients, and in controls. Our results indicate that Fas/FasL system is involved in the inflammatory process in the central nervous system of HAM patients.