Namely, the mean of the percentage of reactive cells (subtracting the mean of unstimulated background) upon IL-15 stimulation was 2.4% in CD4+, 4.7% in CD8+, and 2.7% in CD11b+ cells in HC and 0.1% in CD4+, 0.9% in CD8+, and 1.0% in CD11b+ cells in SLE, respectively (Figure 4). Here, CD4 is linked to systemic lupus erythematosus.