Plasma and IgG obtained from 10 Lambert-Eaton myasthenic syndrome (LES) patients 
(5 with carcinoma, 5 without associated cancer), 6 healthy subjects, and 1 
patient with small-cell lung cancer (SCLC) were examined in their ability to 
recognize chromaffin cell antigens on Western blots. The pattern of antigen 
recognition was compared with the magnitude of inhibition of voltage-dependent 
calcium and sodium currents recorded with the patch-clamp technique from 
chromaffin cells. Eight of the 11 patients with LES and/or SCLC recognized 
plasma membrane proteins and 9 of the patients' IgG interacted with cytoplasmic 
antigens with no apparent pattern of antigen recognition between patients. Also, 
there was no obvious band pattern distinguishing patients with LES from those 
with LES and concurrent SCLC. Eighty percent of the LES patients' antibodies 
were capable of reducing the calcium current (ICa) in chromaffin cells. One of 
the novel findings of this study is that 30% of the patients had produced 
antibodies which were able to inhibit both calcium and sodium currents (INa). 
The heterogeneous response of the IgG on the Western blots does not appear to 
correlate with the efficacy of reducing the inward currents.