High dose immunosuppressive therapy with subsequent autologous stem cell transplantation (ASCT) has proved effective for treatment resistant autoimmune diseases.¹ However, in a number of patients, relapses of autoimmune disease after initial improvement or even remission occur. Until recently, it was impossible to differentiate recent thymic emigrants from residual or peripherally expanded T cells. Douek and coworkers² and later our group³ described a method for detection of T cell receptor excision circles, stable DNA episomes which are formed during T cell receptor rearrangement in the thymus which are not replicated during mitosis, but are diluted during cell divisions.⁴ This study aimed at investigating whether these flares are associated with de novo T cell development.

Peripheral blood mononuclear cells were collected from six patients, mean age 32.5 years, range 24–42 (four with systemic sclerosis (SSc), one with Wegener’s granulomatosis (WG), …