Clonal expansion of limited T cell clonotypes in affected muscle from a patient with post-transplant polymyositis.

Critical roles of T cells in idiopathic polymyositis have been suggested, but, those in polymyositis occurring as GVHD after BMT are poorly understood. We thus investigated T cell clonality in a patient with post- transplant polymyositis. As a result, T cell receptor beta chains used various BV families in peripheral blood, but only one BV family (BV7) in affected muscle. Importantly, T cells proliferated oligoclonally both in the peripheral blood and the muscle, however, the expanded clonotypes were completely different. Taken together, T cells expanded in the muscle, possibly stimulated by limited kinds of antigens, may drive myositis.