Immunoglobulin G of systemic sclerosis patients changed expression of markers on peripheral blood mononuclear cells and secretion of cytokines. Peripheral blood mononuclear cells (PBMCs) from healthy donors (HD) were stimulated for 8 to 20 hours in vitro by either immunoglobulin (IgG) from healthy donors (HD-IgG) or systemic sclerosis (SSc) patients (SSc-IgG). Protein expression of cell surface markers (A) CD14 and (B) CD16 were measured on monocytes by flow cytometry, density is represented by the median fluorescence intensity (MFI). (C) The soluble protein CD14 (sCD14), as well as the cytokines (D) interleukin 8 (IL-8) and (E) chemokine (C-C motif) ligand 18 (CCL18), were measured in the supernatants by enzyme-linked immunosorbent assay. Data derived from three independent experiments done with a total of five HD-IgG and ten SSc-IgG normalized to the unstimulated control. Statistical analysis was done by Mann–Whitney U test. Data are shown as box-and-whisker plots (Tukey). +P < 0.1, *P < 0.05 and **P < 0.01.