Abstract
The neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) plays an important role in immune privilege by its suppression of inflammation, and its induction of regulatory T cells. This finding led us to test the possibility that we can use alpha-MSH to suppress autoimmune diseases, and promote re-establishment of immune tolerance to autoantigens. To test this possibility, SJL mice with experimental autoimmune encephalomyelitis (EAE) were injected with alpha-MSH at the first signs of paralysis. The alpha-MSH-treated mice in comparison with untreated EAE mice had a profound diminishment in the severity and tempo of EAE. The spleen cells in alpha-MSH-treated EAE produced TGF-beta in response to PLP-antigen stimulation in contrast to untreated mice spleen cells that produced IFN-gamma. When the alpha-MSH-treated EAE mice were reimmunized there was a delay of a week before the second episode of EAE. Although this delay maybe because of the induction of TGF-beta-producing spleen cells by the alpha-MSH-treatment, it was not adequate to suppress IFN-gamma-production by PLP-antigen stimulated spleen cells from untreated mice, nor able to suppress the eventual second episode of EAE. Therefore, the injection of alpha-MSH at the onset of paralysis is extremely effective in diminishing the severity and tempo of EAE, and the subsequent induction of potential PLP-specific Treg cells suggests that an alpha-MSH therapy could be attempted as part of a therapeutic regiment to impose immunoregulation and immunosuppression on an autoimmune disease of the central nervous system.