Anti‐NKH‐1 antibody specifically stains unmyelinated fibres and non‐myelinating Schwann cell columns in humans

Anti-NKH-1 antibody recognizes an isoform of the neural cell adhesion molecule (N-CAM) that is involved in cell-cell interactions during embryonic stages and has been detected in skin autonomic nerves. The specificity of anti-NKH-1 antibody for human unmyelinated fibres (UF) and the distribution of the antigens recognized by this antibody at the ultrastructural level, were evaluated by immunohistochemistry and immunoelectron microscopy on nerve biopsy samples from patients with normal nerve biopsies and a variety of peripheral neuropathies. The anti-NKH-1 antibody strongly stained all unmyelinated fibres while no myelinated fibre was stained. Autonomic nerve fibres were visualized at the periphery of blood vessels. Immunoelectron microscopy showed that the antigen recognized by the antibody was located at Schwann cell-axon interfaces and in portions of joined Schwannian surfaces, i.e. along mesaxons of non-myelinating Schwann cells. Expression of NKH-1 was basically similar in normal and diseased nerves as expression of NKH-1 was similar at the level of apposed plate-like Schwann cell processes than along normal mesaxons. The extent of labelling of diseased nerves by the anti-NKH-1 antibody likely depended on the number of residual Schwann cell columns observed by light microscopy.