Diabetes Mellitus Is a Possible Risk Factor for Nodo-paranodopathy With Antiparanodal Autoantibodies

Different binding and pathogenic effect of neurofascin and contactin-1 autoantibodies in autoimmune nodopathies

Introduction

IgG4 autoantibodies against paranodal proteins are known to induce acute-onset and often severe sensorimotor autoimmune neuropathies. How autoantibodies reach their antigens at the paranode in spite of the myelin barrier is still unclear.

Methods

We performed in vitro incubation experiments with patient sera on unfixed and unpermeabilized nerve fibers and in vivo intraneural and intrathecal passive transfer of patient IgG to rats, to explore the access of IgG autoantibodies directed against neurofascin-155 and contactin-1 to the paranodes and their pathogenic effect.

Results

We found that in vitro incubation resulted in weak paranodal binding of anti-contactin-1 autoantibodies whereas anti-neurofascin-155 autoantibodies bound to the nodes more than to the paranodes. After short-term intraneural injection, no nodal or paranodal binding was detectable when using anti-neurofascin-155 antibodies. After repeated intrathecal injections, nodal more than paranodal binding could be detected in animals treated with anti-neurofascin-155, accompanied by sensorimotor neuropathy. In contrast, no paranodal binding was visible in rats intrathecally injected with anti-contactin-1 antibodies, and animals remained unaffected.

Conclusion

These data support the notion of different pathogenic mechanisms of anti-neurofascin-155 and anti-contactin-1 autoantibodies and different accessibility of paranodal and nodal structures.

A Case of Demyelinating Neuropathy with Markedly Elevated Serum IgG4 Levels and Anti-Contactin 1 IgG4 Antibody

We herein report a 77-year-old man with a 4-month history of progressive gait and sensory disturbances of the extremities. A nerve conduction study indicated demyelinating polyneuropathy. Serum IgG4 levels and anti-contactin 1 IgG4 antibodies were markedly increased. The sural nerve biopsy specimen showed IgG4-positive plasma cell infiltration in the epineurium. Treatment with steroids resulted in an amelioration of functional status, improvement of nerve conduction parameters, decreased serum IgG4 levels, and negative conversion of anti-contactin1 antibody. Further studies are needed to clarify the significance of IgG4-positive plasma cell infiltration in anti-contactin 1 antibody-positive neuropathies.