Autoimmunity and the pathogenesis of myocarditis.

T he ability to distinguish between self versus nonself is the most salient feature of the immune system. It is of vital importance for the immune system to mount vigorous humoral and cellular responses to foreign antigens. On the other hand, it is equally important for the immune system to be tolerant against self-antigens. Tolerance can be maintained either by physical elimination (clonal deletion) or functional inactivation (clonal anergy) of the autoreactive T or B cells. Several excellent reviews have explored in depth the mechanisms by which clonal deletion or anergy might occur.1-5 The failure to delete or inactivate autoreactive T or B cells would lead to generalized or organ-specific autoimmunity. In this issue of Circulation, Sharaf and colleagues show that the cardiac sarcoplasmic reticulum calcium ATPase may be a candidate autoantigen in experimental cardiomyopathy. I will briefly review key concepts in immunology before discussing the validity of this claim.