Cluster of differentiation 9 (CD9), a protein of the tetraspanin family present in the paranode of Ranvier, was identified as a potential candidate antigen using human cauda equina as the substrate for IP studies with typical CIDP cases but, again, this was not confirmed in ICC experiments using CD9-transfected HEK cells. This evidence concerns the gene PMP22 and intrahepatic cholangiocarcinoma.