[The expansion of NK CD56+ cells with reduced cytotoxicity in a female patient with systemic sclerosis].

An absolute and relative increase of circulating CD56+ (NKH1, Leu19) natural killer cells has been found in a patient with systemic sclerosis. The expanded natural killer cells exhibited reduced natural killer activity and antibody-dependent cell-mediated cytotoxicity. Furthermore, the limiting dilution analysis of spontaneous in vitro immunoglobulin synthesis demonstrated that the precursor frequency of immunoglobulin-secreting cells and the "single-hit" kinetics of the titration curve were similar to healthy controls, but strongly different from previously reported patients in whom CD16+NK cell subset was expanded. Thus, our findings might suggest that expanded CD56+ natural killer cells exhibit unique regulatory properties on B cell function in systemic sclerosis.