To search for the source of IL-10 in peripheral blood of SLE patients, we sorted out CD14+ monocytes, CD19+ B cells, CD4+ T cells and the remaining CD14-CD19-CD4- cells from lupus PBMCs using flow cytometry sorting technology (Figure 5A), and measured the mRNA expression of IL-10 in each cell subgroup by real-time PCR. The gene discussed is CD19; the disease is systemic lupus erythematosus.