Immune mechanisms in acute and chronic inflammatory polyneuropathies

Disruption of synaptosomal calcium channel function by Lambert-Eaton myasthenic immunoglobulin is serum-dependent

An autoantibody to nerve terminal Ca2+ channels has been suggested to mediate the pathogenesis of the neuromuscular disorder Lambert-Eaton Myasthenic Syndrome (LEMS). We demonstrated previously that in the presence of control human serum, immunoglobulins isolated from a patient with LEMS reduced flux of Ca2+ into isolated nerve terminals during depolarization. The objective of the present study was to determine the role of serum in reducing uptake of 45Ca2+ into rat brain synaptosomes by LEMS IgG. Depolarization-dependent uptake of 45Ca2+ through voltage-gated Ca2+ channels was determined using synaptosomes incubated with control (disease-free) and LEMS IgG with or without control human serum. In the absence of human serum, LEMS IgG did not reduce uptake of 45Ca2+ into synaptosomes. However, in the presence of control human serum (10% of total incubation volume), 45Ca2+ uptake was reduced significantly by LEMS IgG (2 and 4 mg/ml), but not by IgG from disease-free patients or by 10% (v/v) control human serum alone. This concentration of serum was found to be optimal; higher concentrations produced significant reductions in Ca2+ uptake, whereas at lower concentrations the serum/IgG combination was ineffective. The depressant effect of high concentrations of serum alone on 45Ca2+ uptake was mimicked by equal concentrations of bovine serum albumin suggesting that deficits in 45Ca2+ uptake produced by high concentrations of serum were due to increased protein binding of the radiolabel. Heat-inactivating the serum abolished its ability to interact with the LEMS immunoglobulins to depress 45Ca2+ uptake. This suggested a role for complement in this effect.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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

The immune-mediated disorders of the central and peripheral nervous systems all involve humoral mechanisms in which immunoglobulin, complement and/or other mediators are implicated. The disorders can be characterized by pattern of disease activity, site of immunoglobulin synthesis, humoral mechanism of injury, and presence of one or more concurrent cellular mechanisms of injury. Control of the humoral responses is presumably T-cell dependent. While these disorders should be viewed as having both humoral and cellular components, the specific components of each disorder might predict the response to specific therapeutic approaches.