Expression levels of IFIT4 in patients with SLE and healthy control individuals. (a) Total RNA from the peripheral blood mononuclear cells (PBMCs) of 108 systemic lupus erythematosus (SLE) patients and 46 healthy donor (HDs) was isolated, and the relative expression level of IFIT4 mRNA was determined by real-time quantitative RT-PCR. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was co-amplified as an internal control to normalize the amount of IFIT4 mRNA. All experiments were repeated three times with similar results. Horizontal lines indicate the mean (P < 0.001, Mann-Whitney test). (b,c) Total protein was extracted from the PBMCs of 24 SLE patients and 24 HD control individuals. IFIT4 protein expression levels were detected using Western blotting. β-Actin was used as a protein loading control. A set of random data from eight SLE patients and eight HD controls is presented (P = 0.002, Mann-Whitney test). (d) Monocytes from three SLE patients and three HDs were isolated using magnetic beads. The IFIT4 protein expression level in these monocytes was determined by Western blotting. IFIT4, interferon-induced protein with tetratricopeptide repeats 4.