Macrophage differentiation antigens in acute and chronic autoimmune polyneuropathies

The pathological differential diagnosis between potentially treatable autoimmune neuropathies and degenerative neuropathies is often difficult if major T-cell infiltrates are absent in sural nerve biopsies. Since it is suggested that macrophages play a central pathogenetic role in inflammatory neuropathies, we investigated the expression of macrophage differentiation antigens associated with acute (MRP14 and 27E10 antigens) and more chronic inflammation (MRP8 and 25F9 antigens) in 76 sural nerve biopsies from patients with Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, other inflammatory neuropathies, hereditary neuropathies and normal sural nerves. Macrophage differentiation antigens were immunocytochemically detected in a majority of inflammatory biopsies but rarely in non-inflammatory disease controls and normal-looking nerves. Quantification of labelled endoneurial cells revealed significantly elevated cell counts compared with controls. In individual biopsies, elevated levels of one differentiation antigen were not necessarily associated with high expression of the other antigens, pointing to functional heterogeneity of endoneurial macrophages. Endoneurial cell counts for at least one of the differentiation markers that were greater than in any of the non-inflammatory control nerves were found in two-thirds of all inflammatory biopsies, whereas T-cell counts and in particular total macrophage counts were less sensitive in picking up biopsies from patients with inflammatory neuropathies. Antibodies to macrophage differentiation antigens are additional simple and helpful diagnostic tools in differentiating autoimmune from non-inflammatory neuropathies in sural nerve biopsies.