Thymus-dependent (T) lymphocyte deficiency in progressive systemic sclerosis.

Circulating thymus-dependent (T) lymphocytes were estimated in twenty-seven patients with progressive systemic sclerosis (PSS) and in forty-five normal controls using the property of T lymphocytes to form rosettes with sheep red blood cells. The patients with PSS were found to have a reduction of T lymphocytes which correlated with the extent of visceral involvement by the disease, those with the lowest counts having the most extensive disease. These findings support the suggestion that immunological factors may be involved in the pathogenesis of PSS.