Major histocompatibility complex class II expression and macrophage responses in genetically proven Charcot-Marie-Tooth type 1 and hereditary neuropathy with liability to pressure palsies

This study examined major histocompatibility complex (MHC) class II expression and macrophage infiltration in sural nerve biopsies from patients with genetically proven Charcot-Marie-Tooth (CMT) 1A and 1B and hereditary neuropathy with liability to pressure palsies (HNPP) by immunocytochemistry. In both young and older patients with duplication of the PMP22 gene, MHC class II expression was consistently up-regulated and not closely related to the extent of macrophage infiltration. On the other hand, MHC class II expression was more variable in CMT1A and CMT1B caused by point mutations and in HNPP. The extent of nerve pathology as assessed by teased fiber preparations or electron microscopy was not predictive for the degree of MHC class II expression in CMT1/HNPP. We conclude that MHC class II up-regulation is a common feature in hereditary neuropathies. As shown for the animal model of globoid cell dystrophy, it is conceivable that increased expression of MHC class II molecules in CMT1 and HNPP accelerates nerve pathology.