CVID and CVID/GLILD patients demonstrate increased frequency of CD21lo B cells. B cell subpopulation percentages derived from manual gating of mass cytometry data for CD27+ B cells (a), CD21lo B cells (b), mature naïve B cells (c), immature naïve B cells (d), IgM memory B cells (e), pre switched B cells (f), atypical memory B cells (g), anergic B cells (h), c-delta switched B cells (i), and CXCR5+ B cells (j). CXCR5 median intensity on CD21lo B cells (k). Unsupervised PhenoGraph clustering of CD19+ cells (l) and surface marker expression (m). Cluster frequencies corresponding to isotype switched B cells (cluster 1) and CD21lo B cells (cluster 14) (n). Error bars represent median and 95% CI. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Not significant unless stated by asterisk in figure. Kruskal–Wallis accounting for multiple comparisons was used for statistical significance