PTPRC and systemic lupus erythematosus: First, the proportion of all Ki-67+ cells among CD45+ cells in SLE patients correlated with SLEDAI (ρ = 0.389, P = 0.009), titer of anti-DNA antibody (ρ = 0.540, P < 0.001), C3 level (ρ = ‐0.366, P = 0.015), and C4 level (ρ = ‐0.425, P = 0.004) but not platelet count (Fig. 2A).