Lack of natural killer cell augmentation in vitro by human interferon gamma in a subset of patients with systemic sclerosis

Systemic sclerosis (SSc) is a generalized connective tissue disorder characterized by fibrosis of skin and various viscera. Natural killer (NK) cells are a subset of lymphocytes that can lyse targets without prior sensitization. Few studies have tried to assess NK cell function in patients with SSc. To evaluate NK cell cytotoxicity in patients with SSc and to see the extent of its augmentation in vitro by human interferon (hIFN) gamma in the clinical subset of limited and diffuse cutaneous diseases, we evaluated 27 patients with SSc and 22 age- and sex-matched controls by ⁵¹Cr release assay. Fifteen patients had limited cutaneous disease (mean disease duration 6.2 ± 2.7 years) and 12 diffuse cutaneous disease (mean disease duration 5.7 ± 2.4 years). Patients with limited SSc had significantly higher baseline NK cell function than controls (p < 0.05) and the augmentation following in vitro stimulation with hIFN gamma was negligible. Patients with diffuse SSc had lower baseline NK cell cytotoxicity than controls but this was not statistically significant. Augmentation with hIFN gamma in this group was comparable to controls. This study suggests that NK cells may have a role in the pathophysiology of this disease.