Reduced circulating natural killer T cells and gamma/delta T cells in patients with systemic sclerosis

Objective. To evaluate peripheral blood mononuclear cells (PBMC) expressing natural killer (NK) cell surface markers (CD16 and CD56, in both CD3- and CD3+ cells) and gamma/delta T cell receptors (TCR) involved in non-MHC-restricted cytotoxicity, assessing their possible relationship with clinical and laboratory variables in patients with systemic sclerosis (SSc). Methods. We submitted 50 patients with SSc to detailed clinical and laboratory assessment, and also performed PBMC subset analyses by direct dual immunofluorescence and flow cytometry. Results. No statistically significant differences were found in the percentages or the absolute numbers of total lymphocytes, of B cells, and of CD4+ T cells. The absolute number of CD8+ cells was lower (p < 0.03), while HLA-DR+ elements were higher in frequency (p < 0.03) in SSc patients than in healthy controls. SSc patients had lower values (both percentage and absolute number) of NK-T cells (p < 0.01 and p < 0.003, respectively) and of T cells expressing gamma/delta TCR (p < 0.01 and p < 0.005, respectively); whereas NK cells were marginally but not significantly decreased. The absolute number of NK-T cells showed an inverse correlation to erythrocyte sedimentation rate values (p < 0.03; r(s) = -0.306), percentage of gamma-globulins (p < 0.01; r(s) = -0.353), and serum concentrations of IgG (p < 0.02; r(s) = -0.334). Conclusion. Impairment of NK-T cells and of T cells expressing gamma/delta TCR may lead to downregulation of normal immune response, and seems to be important for immunological and inflammatory aspects of SSc.