Although a moderate to high positive correlation of CD19 MFI was observed intra-individually among B cell subsets in both SLE and HD (not shown), CD19 MFI was significantly different across subsets (Kruskal-Wallis test p < 0.0001 in both SLE and HD), with the DN subset having the lowest and the USWM the highest expression level (Fig. 3B). Here, CD19 is linked to systemic lupus erythematosus.