Skeletal muscle cells: from local inflammatory response to active immunity.

The skeletal muscles are the major living component of the human body. They are constituted by stable cells, the myofibres, and by adult multipotent stem cells, the satellite cells, which can multiply to regenerate and repair the damaged tissues. Injections of DNA in muscle cells have been used to produce recombinant proteins with opposite goals: somatic reparation of genetic defects, which needs to elicit no inflammatory or immune response, and DNA vaccination, which needs a robust immune response. Because of possible therapeutical interventions, a growing body of information is being produced dealing with every aspect of the myofibres during inflammatory and autoimmune responses: skeletal muscle-antigen presenting cell (APC) interaction and intrinsic APC capabilities of myoblasts and myocytes, the response to released cytokines and their endogenous production, the regulation of Toll-like receptors and major histocompatibility complex expression. According to these data, the muscle tissue is now emerging no longer as a passive bystander, but more as an active player that, when correctly manipulated, can drive tolerance or immunization to these de novo produced proteins. In the present review, we summarize the recent developments on the control of muscle immune function.