In patients with SLE and HCs, the mean salivary IGHG3 level was 3078.9 ± 2473.8 and 1413.6 ± 1075.3 ng/mL, respectively (p < 0.001), the mean serum IGHG3 level was 478.1 ± 16.09 and 364.4 ± 97.9 μg/mL, respectively (p < 0.001), and the mean urinary IGHG3 level was 64.0 ± 74.5 and 27. The gene discussed is IGHG3; the disease is systemic lupus erythematosus.