CD19 and systemic lupus erythematosus: The results of patients with SLE under the influence of the MSC secretome are the following: regarding the percentage of CD19+CD80+ 36.17 ± 20.33% vs. 34.30 ± 18.22%, p = 0.1089, and the CD80 mean fluorescence intensity (MFI) 127.66 ± 30.01 vs. 132.92 ± 28.44, p = 0.0887, respectively (Figure 3A(a),B(a)).