Under the influence of UC-MSC media, the percentage of CD19+ cells expressing the PD-1 marker was significantly reduced compared to the control media-treated CD19+ cells in HVs (5.28 ± 3.62% vs. 6.87 ± 5.01%; p= 0.0273) and patients with SLE (22.07 ± 22.82% vs. 29.14 ± 20.29%; p = 0.0011) (Figure 5A(b)). Here, CD19 is linked to systemic lupus erythematosus.