In vitro induction of CD25+ CD4+ regulatory T cells by the neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH).
Recently, we have found that the neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) not only suppresses IFN-gamma production, but also induces TGF-beta1 production by activated effector T cells. These alpha-MSH- treated effector T cells function as regulatory T cells in that they suppress IFN-gamma production and hypersensitivity mediated by other effector T cells. Experimental autoimmune uveoretinitis (EAU) was suppressed in its severity and incidence in mice that were injected with primed T cells activated in vitro by APC and antigen in the presence of alpha-MSH. Moreover, it appeared that alpha-MSH had converted a population of effector T cells polarized to mediate hypersensitivity into a population of T cells that now mediated immunoregulation. To characterize these alpha-MSH- treated T cells, primed T cells were TCR-stimulated in the presence of alpha-MSH in vitro and their lymphokine profile was examined. Such effector T cells displayed enhanced levels of TGF-beta1 production and no IFN-gamma or IL-10, with IL-4 levels remaining unchanged in comparison with inactivated T cells. In addition, if soluble TGF-beta receptor II was added to cocultures of alpha-MSH-treated T cells and activated Th1 cells, the alpha-MSH-treated T cells could not suppress IFN-gamma production by the Th1 cells. These results suggest that alpha-MSH induces T cells with a regulatory lymphokine pattern, and that through their production of TGF-beta1 these cells suppress other effector T cells. Examination of the alpha-MSH-treated T cells showed that alpha-MSH did not alter the phosphorylation of CD3 molecules following TCR engagement. Primed T cells express the melanocortin 5 receptor (MC5r), a receptor that is linked to an intracellular signalling pathway shared by other cytokine receptors. Blocking the receptor with antibody prevented alpha-MSH from suppressing IFN-gamma production by the activated regulatory T cells, suggesting that alpha-MSH immunoregulation is through the MC5r on primed T cells. Surface staining and cell sorting of the alpha-MSH- treated primed T cells showed that the regulatory T cells are CD25+ CD4+ T cells. From these results we find that alpha-MSH can mediate the induction of CD25+ CD4+ regulatory T cells. These regulatory T cells require specific antigen for activation, but through non-specific TGF-beta1-mediated mechanisms they can suppress other effector T cells.
Taylor
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A
Schepens Eye Research Institute and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts 02114, USA. awtaylor@vision.eri.harvard.edu
Namba
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K
D000818:Animals; D001327:Autoimmune Diseases / Q000097:blood / Q000188:drug therapy / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000276:immunology; D005434:Flow Cytometry; D007371:Interferon-gamma / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000276:immunology; D018043:Receptors, Corticotropin / Q000378:metabolism; D015375:Receptors, Interleukin-2 / Q000378:metabolism*; D044101:Receptors, Melanocortin; D012173:Retinitis / Q000097:blood / Q000188:drug therapy / Q000276:immunology*; D012177:Retinol-Binding Proteins / Q000276:immunology; D016212:Transforming Growth Factor beta / Q000096:biosynthesis; D000521:alpha-MSH / Q000494:pharmacology*; D000099214:Retinol-Binding Proteins, Interstitial
D005136:Eye Proteins; D007371:Interferon-gamma; D010446:Peptide Fragments; D018043:Receptors, Corticotropin; D015375:Receptors, Interleukin-2; D044101:Receptors, Melanocortin; D012177:Retinol-Binding Proteins; D016212:Transforming Growth Factor beta; D000521:alpha-MSH; D000099214:Retinol-Binding Proteins, Interstitial; C086971:melanocortin 5 receptor