However, for patients with CVID, those with severely reduced isotype-switched memory B cells (defined as <2% of total CD19+B cells) (41) had significantly higher serum bacterial 16S rDNA levels as compared with those with higher numbers of these cells (mean 19.27 copies/L, range 0.4–85 copies/L vs. mean 10.24 copies/L, range 1.14–34.9 copies/L, respectively, P = 0.0008, Figure 4D). This evidence concerns the gene CD19 and common variable immunodeficiency.