HLA-DR expression in peripheral neuropathies: the role of Schwann cells, resident and hematogenous macrophages, and endoneurial fibroblasts.

The expression of HLA-DR and the macrophage marker CD 68 was studied in 44 sural nerve biopsies from patients with inflammatory and non-inflammatory neuropathies and controls using immunohistochemistry on non-osmicated semithin sections, a technique that has not been used before in such a biopsy study. Most HLA-DR-immunoreactive (ir) cells were fibroblasts, macrophages or perineural cells, some were perivascular and endothelial cells, and only few were Schwann cells. Counts of immunoreactive cells revealed (a) increased HLA-DR expression in severe as compared to less severe neuropathies and to controls, (b) no correlation between the numbers of HLA-DR-ir cells and CD 68-ir macrophages, and (c) no close correlation between diagnostic groups and the number of HLA-DR-ir cells, but higher numbers in inflammatory neuropathies. We conclude that endoneurial fibroblasts and macrophages as antigen-presenting cells may be mediators in various peripheral nerve diseases, not only in inflammatory disorders.