Co-localization of secretoneurin immunoreactivity and macrophage infiltration in the lesions of experimental autoimmune encephalomyelitis.

Secretoneurin, a novel neuropeptide, has recently been shown to attract monocytes. In our present study we have tested whether the local presence of secretoneurin within the CNS of the rat may influence the topographical distribution of inflammatory infiltrates in acute T-cell mediated encephalomyelitis. Experimental allergic encephalomyelitis was induced by passive transfer of myelin basic protein-reactive T-lymphocytes and the distribution of T-cells and macrophages was studied at day 3, 4 and 7 after transfer. In the same sections secretoneurin immunoreactivity was visualized by immunohistochemistry. A clustering of macrophages, but not of T-lymphocytes, was seen at sites of secretoneurin immunoreactivity in all stages of experimental autoimmune encephalomyelitis. Our data indicate for the first time that local neuropeptides may play a role in leucocyte recruitment into inflammatory lesions of the CNS.