The recognition of self-antigens and autoimmune disease

GM-CSF promotes inflammatory dendritic cell formation but does not contribute to disease progression in experimental autoimmune myocarditis

BACKGROUND

Granulocyte macrophage-colony stimulating factor (GM-CSF) is critically required for the induction of experimental autoimmune myocarditis (EAM), a model of post-inflammatory dilated cardiomyopathy. Its specific role in the progression of myocarditis into end stage heart failure is not known.

METHODS AND RESULTS

BALB/c mice were immunized with myosin peptide and complete Freund's adjuvant at days 0 and 7. Heart-infiltrating inflammatory CD133(+) progenitors were isolated from inflamed hearts at the peak of inflammation (day 21). In the presence of GM-CSF, inflammatory CD133(+) progenitors up-regulated integrin, alpha X (CD11c), class II major histocompatibility complex, CD80 and CD86 co-stimulatory molecules reflecting an inflammatory dendritic cell (DC) phenotype. Inflammatory DCs stimulated antigen-specific CD4(+) T cell proliferation and induced myocarditis after myosin peptide loading and adoptive transfer in healthy mice. Moreover, GM-CSF treatment of mice after the peak of disease, between days 21 and 29 of EAM, transiently increased accumulation of inflammatory DCs in the myocardium. Importantly, bone marrow-derived CD11b(+) monocytes, rather than inflammatory CD133(+) progenitors represent the dominant cellular source of heart-infiltrating inflammatory DCs in EAM. In contrast, GM-CSF treatment neither affected numbers of heart-infiltrating CD45(+) and CD3(+) T cells nor the development of post-inflammatory fibrosis.

CONCLUSIONS

GM-CSF treatment promotes formation of inflammatory DCs in EAM. In contrast to the active roles of GM-CSF and DCs in EAM induction, GM-CSF-induced inflammatory DCs neither prevent resolution of active inflammation, nor contribute to post-inflammatory cardiac remodelling. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Cardiac Pathways of Differentiation, Metabolism and Contraction.

Beta-arrestin and arrestin are recognized by autoantibodies in sera from multiple sclerosis patients

Multiple sclerosis (MS), one of the most common chronic neurologic diseases, is characterized by the presence of multiple plaques of demyelination throughout the central nervous system. Although the etiology of the disease has not been established, it is believed to involve autoimmune mechanisms. We have examined sera from patients with MS for the presence of antibodies to antigens from brain and retina. Immunoblot analysis of soluble fraction of proteins from bovine brain revealed a prominent band at 45 kDa stained with sera of 8-14 patients with MS. In two patients with MS, serum antibody titers during relapse were higher compared with those when the patients were in remission. These antibodies were undetectable in cerebrospinal fluid of our MS patients and additionally were absent in sera of patients with other neurological diseases and normal control subjects. Furthermore, immunoblot analysis of the soluble fraction from bovine retinal rod outer segments revealed a prominent protein band at 48 kDa stained with MS sera. This antigen was purified to homogeneity from bovine retinal outer segments and identified as arrestin. Additionally, sera from MS patients reacted with purified beta-arrestin 1, a 45-kDa protein homologous to arrestin that is found in various tissues. Using limited proteolysis of arrestin and a competitive ELISA test with a synthetic peptide, we identified the recognition site(s) for antibodies in sera of MS patients at a dominant immunogenic site on arrestin located at the C-terminal region of the molecule. We suggest that the presence of circulating antibodies reactive with beta-arrestin or arrestin may be related to the course of MS progression.