GFAP expression of human Schwann cells in tissue culture

We have studied the expression of the intermediate filament (IF) proteins, vimentin and glial fibrillary acidic protein (GFAP), in cultured human Schwann cells (SC) from patients with different neuropathies and normal control cases. SC cultures from sural nerve biopsies of 8 subjects with axonal neuropathies, 8 with demyelinating neuropathies and 3 normal controls were included in this study and processed with double immunofluorescence technique, using anti-vimentin and anti-GFAP antibodies, during the 2nd, 4th and 6th week of culture. Five cultures incubated with anti-GFAP antibodies were also processed for immunoelectron microscopy. Specificity tests of the used antibodies were performed. We have found that: (1) cultured human SC constantly express vimentin; (2) SC from normal controls are GFAP-negative in the first period of culture; (3) SC from pathologic nerves can contain GFAP-immunoreactive IF and the percentage of GFAP-positive SC is higher in axonal than in demyelinating neuropathies; (4) during the permanence in culture human SC from both normal and pathologic cases acquire the ability to synthesize GFAP. The obtained data suggest that the removal from axonal contact and the resulting loss of myelinating function induce a cytoskeletal cellular response in human SC characterized by the cytoplasmic accumulation of GFAP-immunoreactive IF.

Direct immunofluorescence in sural nerve biopsies

Direct immunofluorescence (DIF) has been carried out in 66 sural nerve biopsies using antibodies against human IgG, IgA, IgM, C3, C4, albumin, fibrinogen, and kappa- and lambda-chains. In 37 out of 63 (59%) different neuropathies immunoglobulins or other plasma proteins were found within the peripheral nerves. IgM along the myelin sheaths were found in monoclonal IgM-K-associated demyelinating peripheral neuropathy and chronic inflammatory demyelinating peripheral neuropathy. IgM within the perineurium were detected in hereditary, diabetic, paraneoplastic, paraproteinemic and neuropathies of unknown cause. In inflammatory, vasculitic, hereditary and toxic neuropathies fibrinogen, albumin, IgG and IgA were variably observed in endoneurium, endoneurial vessels, perineurium and epineurial vessels. In our experience DIF appears to be just an unspecific marker of sural nerve pathology. In selected cases however DIF may be helpful in the diagnosis or in better understanding the pathogenetic mechanisms of the disease.