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Evidence is accumulating that anti-ganglioside antibodies may well mediate both Miller Fisher syndrome and the acute motor axonal form of Guillain-Barré syndrome 1 but such antibodies are not present in most patients with the more common demyelinating forms of Guillain-Barré syndrome. T cells are thought to play an important part in the pathogenesis of the neuropathy in these patients, by analogy with experimental allergic neuritis and from histological studies of biopsy and postmortem peripheral nerve material. Furthermore many anti-ganglioside antibodies are of the IgG isotype normally requiring T cell help in their production.
We have previously proposed that γδ T cells might have a role in the pathogenesis of inflammatory demyelinating neuropathy after Campylobacter jejuni infection of the gut, because of their potential to react with carbohydrate ligands.2 It is possible to culture γδ T cell lines from peripheral nerve biopsy material from patients with demyelinating forms of Guillain-Barré syndrome2 and demonstrate immunostained γδ T cells in nerve infiltrates.3 CD1 is an essential presentational molecule in the interaction of γδ T cells and their ligands and we and others have shown that CD1 is upregulated in biopsy material from both Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy.3,4
To investigate the hypothesis that γδ T cells from patients with Guillain-Barré syndrome might respond to non-protein antigens, we carried out a 6 day proliferation assay using peripheral blood mononuclear cells (PBMCs) from 23 patients with Guillain-Barré syndrome using techniques similar to those previously reported.5 Nine of these patients were known to have serological evidence of preceding C jejuni infection. An isolate of C jejuni cultured from a patient with Guillain-Barré syndrome (Penner type 04) was used at a concentration of 5 μg/ml and treated with a standard protocol of proteinases to abrogate T cell responses to peptides.6 The effectiveness of this protocol in removing peptides was assessed by overloading an SDS-PAGE gel with this antigen and confirming that no protein remained in the preparation. Patients with multiple sclerosis, other neurological diseases, and healthy controls were studied for comparison. Proliferative responses among these groups are shown in figure 1. Proliferative responses greater than normal controls or other neurological diseases (stimulation index ≥10) were seen in two patients with Guillain-Barré syndrome and in two patients with multiple sclerosis. In one patient with Guillain-Barré syndrome the stimulation index was >52 times the background level.
Ethical permission was obtained to peform sural nerve biopsies in eight patients with Guillain-Barré syndrome after C jejuni infection and expression of CD1b by immunohistochemistry was upregulated in seven, confirming similar findings to those found in two patients studied by Khalili-Shirazi et al.3
Our results suggest that a proportion of patients with demyelinating disorders show evidence of proliferative responses to non-protein antigens. Our results are still preliminary and we propose further work to determine the exact nature of the responsible antigen so that we can compare our results with serological detection of specific anti-ganglioside antibodies. The results are remarkable as it is known that very many different carbohydrate antigenic determinants are present in different strains of C jejuni and our antigen was obtained from a single isolate, providing an extremely limited array of possible antigens. Whereas we anticipated such responses in patients with Guillain-Barré syndrome the positive results in patients with multiple sclerosis are also of interest. These results would accord with studies implicating immunity to non-protein antigens in multiple sclerosis, including a study in which it was possible to generate ganglioside specific clones from patients with multiple sclerosis that were restricted by CD1b.7
Further study of non-classic T cell responses in both Guillain-Barré syndrome and multiple sclerosis may prove informative.
We acknowledge support for our ongoing research from both The Wellcome Trust and the Guillain-Barré Syndrome Support Group and are grateful to Dr Cheeseborough for advice about the C jejuni serology.