Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic autoimmune disorder 
caused by an IgG-mediated reduction in number of presynaptic voltage-gated 
calcium channels (VGCC) at the neuromuscular junction. In at least 50% of cases, 
the stimulus for antibody production may be VGCC on small cell lung cancer 
(SCLC). In this study membranes isolated from a human small cell lung cancer 
xenograft (Mar), that bound [3H]PN200-110, a VGCC antagonist, were subjected to 
Western blotting using plasma from 12 LEMS patients and eight controls. Although 
one band recognised by 3/12 LEMS IgGs might be associated with the VGCC, a 
number of other proteins were recognised both by LEMS plasma, and by plasma from 
patients with other disorders. The results illustrate the difficulties found 
using Western blotting with autoimmune plasma to identify specific polypeptides 
in a crude antigen preparation.