Hallmarks of the idiopathic inflammatory myopathies are muscle weakness and abnormal findings in muscle biopsies. Serologically, a growing number of myositis-specific and -associated antibodies have been defined and together with the histological findings patients are subdivided into polymyositis (PM), dermatomyositis (DM) and inclusion body myositis (IBM).
The presence of autoantibodies point towards a role for antigen-specific CD4+ T cells, but so far only few studies have addressed adaptive immune responses in myositis. This notion is further supported by associations to HLA.
We have during the last years focused on a subset of highly differentiated T helper cells lacking the costimulatory molecule CD28. These cells have been coined CD28null T cells, and are overrepresented in both PM and DM (Fasth et al J Immunol 2009) and IBM (Pandya et al Arthritis Rheum 2010).
CD28null T cells are oligoclonally expanded T cells and can be either CD4 or CD8. Irrespective, they are devoted effector T cells making cytokines and being cytotoxic. So far the best described antigen-specificity amongst CD28null T cells is for cytomegalo virus (CMV), but it is likely that other specificities can also be found.
Our working hypothesis is that CD28null T cells actively contribute to muscle dysfunction in affected tissue. Indeed, these cells are often persistently found in the biopsies even after aggressive treatment and may thus participate in the chronicity of this syndrome.
During the lecture I will summarize our recent data on the functionality and specificity of T cells in patients with inflammatory myopathies.
Disclosure of Interest None Declared