Inflammatory cells in the peripheral nervous system in motor neuron disease

We examined post-mortem material of the peripheral nervous system of 26 cases of motor neuron disease (MND) for the presence of lymphocyte subsets and macrophages. Findings were quantified and compared with those in control nerves. Lymphocytes in chronic and acute axonal degeneration were studied in sural nerve biopsy and animal material. Signs of demyelination were studied in MND and controls with infiltrates of T cells. A few T lymphocytes were scattered diffusely within the fascicles. The numbers did not differ between MND and controls. About half of the T cells was positive for CD45RA, the other half being positive for CD45RO. T cells were negative for CD25, CD54 and major histocompatibility complex (MHC)-class II. There were hardly any B lymphocytes. The numbers of lymphocytes in nerves with and without axonal degeneration did not differ. Increased MHC class II expression was present on denervated Schwann cells and macrophages in MND and in sural nerves with axonal degeneration. Macrophages were increased in number and in size, both in MND and in control material with axonal degeneration. No signs of demyelination were present either in MND or in controls. It is concluded that a T cell-mediated process in peripheral nerves in MND is very unlikely.