Humoral factors in inflammatory disorders of the central and peripheral nervous system

[Plasmapheresis in neurology. Critical analysis of indications and protocols]

Therapeutic plasmapheresis (plasma exchange) in neurology is a matter of discussion. We review the main articles on clinical trials, both controlled and uncontrolled, trying to establish the efficacy and safety of the procedure. Humoral aspects involved in the genesis of the disorder play an important role for its indication in the present time. In myasthenia gravis indications for plasmapheresis are established: in the preparation for thymectomy, in patients with respiratory insufficiency and requiring respiratory prosthesis, after long immunosuppression therapy with rebound effect, when all other forms of therapy failed, and in neonatal myasthenia gravis with special technics. We discuss the indication of plasmapheresis in Guillain-Barré syndrome, multiple sclerosis, chronic inflammatory demyelinating polyneuromyelopathy, HTLV-1 myelopathy, HIV peripheral neuropathy and myelopathy, paraproteinemias, polymyositis, and dermatomyositis. Indications for other diseases are mentioned. Reference is made to the results we observed in 31 cases followed consecutively at Hospital dos Servidores, Rio de Janeiro, from June 1984 to June 1990. In our series 26 were myasthenic patients, 4 patients presented Guillain-Barré syndrome, and 1 multiple sclerosis. Therapeutic plasmapheresis protocols suggested by us are summarized.

In vivo effects of sera from Guillain-Barré subgroups: an electrophysiological and histological study on rat nerves

Serum from 20 patients with Guillain-Barré syndrome (GBS), 10 healthy controls and 10 patients with recent cytomegalovirus, Epstein-Barr virus, or Campylobacter jejuni/coli infections was injected into rat sciatic nerve. The 20 GBS patients consisted of 2 groups of 10 patients with different electrophysiological and clinical disease patterns. The main aim of the study was to investigate possible differences in humoral (auto)-immunity between these subgroups. We found no statistically significant differences in electrophysiological or histological parameters between nerves injected with sera from the 2 GBS groups. The sera of the GBS groups caused significantly more compound muscle action potential reduction at 3 to 5 days postinjection than the healthy control sera. No significant difference in nerve conduction was found between nerves injected with GBS serum and serum of patients with proven infections without GBS. Histological analysis of the same nerves that were studied electrophysiologically showed no significant differences in demyelination or other histological parameters between patients and controls at 5 days postinjection. Based on the findings in this study that sera of GBS groups with important differences in disease pattern and sera of patients with proven infection but without GBS show similar in vivo effects on rat nerves, we suggest it may be more likely that these effects are caused by aspecific serum factors associated with immune-system activation, especially by precedent infections, than by specific disease-related factors such as anti-myelin antibodies.

Immunological specificity and cross-reactivity of anti-acetylcholine receptor and anti-presynaptic membrane receptor antibodies in myasthenia gravis

Antibodies against acetylcholine receptor (AChR), a protein that binds to alpha-bungarotoxin (alpha-BuTx), are characteristic for myasthenia gravis (MG) and are considered to be of importance in the pathogenesis of the disease. Antibodies against a beta-BuTx binding protein, presynaptic membrane receptor (PsmR), have also been reported in most MG patients. We have analysed the specificity and cross-reactivity of antibodies to bovine AChR and PsmR in sera from 11 patients with MG. More than 90% of antibodies to PsmR were adsorbed specifically by PsmR conjugated affinity chromatography. Similarly, more than 90% of anti-AChR antibodies were absorbed by AChR conjugated affinity chromatography. Specificities of antibodies from affinity chromatography were also confirmed by ELISA and agarose isoelectric focusing. However, the antibodies to PsmR and AChR from MG patients' sera showed about 45-55% cross-reactivity, and there was a high correlation between serum levels of both antibodies. The demonstration of anti-PsmR antibodies could be important in documenting presynaptic damage and understanding the pathogenetic process in MG.