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.