Figure 4

SLE serum induces surface expression of CD64 on monocytes. (a) Effect of sera from SLE patients (n = 65) and healthy controls (n = 44) on CD64 expression by healthy control monocytes. PBMCs from healthy donors were cultured in the presence of 25% serum for 19 hours before flow cytometry. ΔMFI was calculated by subtracting baseline CD64 MFI from donor monocytes cultured in autologous serum from the MFI of CD64 expression after incubation with serum from healthy controls or SLE patients. A positive ΔMFI indicates an upregulation of CD64 expression compared with the baseline levels. (b) Bivariate analysis of SLE serum-induced upregulation of CD64 on healthy control monocytes and CD64 expression on monocytes from the SLE serum donors (n = 37; r = 0.36; P < 0.05; Spearman's correlation). (c) Effect of B18R pretreatment on SLE serum-induced CD64 upregulation on healthy control monocytes. Three independent experiments, each using five or more serum samples from SLE patients are depicted. ** P < 0.01; *** P < 0.001 compared with the levels of CD64 induced by SLE-serum without B18R present (Student's t test). (d) Effect of anti-IFN-γ or anti-IL-12 neutralizing antibodies, or isotype control antibody (mouse IgG1) on SLE serum-induced upregulation of CD64 on healthy control monocytes. Bars represent the mean of four independent experiments. Difference in CD64 expression in the presence/absence of B18R was analyzed with Student's t test. (e) Flow-cytometry analysis of CD32 and CD16 expression on healthy control monocytes after incubation with sera from SLE patients or healthy controls, as described in (a).