Background Pilot studies were suggestive for a role of clonal T cells in the pathogenesis of systemic sclerosis (SSc).
Objectives To investigate the presence of clonal T cells in both peripheral blood and skin of a large collection of patients with SSc.
Methods Polymerase chain reaction and high-resolution capillary electrophoresis for detecting T-cell clonality were performed in a series of 126 patients with SSc.
Results Seventy-seven (61%) of 126 patients had clonal T cells in their peripheral blood. In contrast, a clonal T-cell population was present in only four of 29 (14%) age-matched healthy controls (P = 0·03). Older patients were more likely to have clonal T cells than younger patients with SSc (P < 0·0001). Clonal T cells were more commonly detected in the blood of patients with limited cutaneous SSc (48 of 65 patients, 74%) than in those with diffuse cutaneous disease (29 of 61, 48%; P = 0·0002). Lesional skin specimens from 20 of 44 patients (45%) had detectable clonal T-cell populations. There was no correlation between the presence of circulating clonal T cells and lesional clonal T cells, sex, disease duration, extent of skin sclerosis, digital ulcers, organ involvement (e.g. interstitial lung disease, kidney disease, oesophagus involvement), treatment of SSc, or autoantibody profile.
Conclusions Many patients with SSc have expanded clonal T cells in their peripheral blood and skin. These clonal T cells could play a critical role in the pathogenesis of SSc, especially in limited cutaneous disease.