Immunohistochemical analysis of sural nerve biopsies from CIDP patients revealed significantly reduced Cldn5 expression at endoneurial endothelial junctions, even in regions lacking overt edema, suggesting that immune processes selectively downregulate Cldn5, potentially increasing barrier permeability to leukocytes and pathogenic antibodies [131]. This evidence concerns the gene CLDN5 and chronic inflammatory demyelinating polyradiculoneuropathy.