Overview of the gating strategy for panel ONE 05: B cell subsets. Identification of B cell subsets was based on previously published classifications [36, 37]. The data file of the stained lysed (EDTA spiked) whole blood (WB) was analyzed as follows: exclusion of non-single events and gating of CD45+ leukocytes as shown for panel ONE 01 (Figure 2); gating of CD19+ B cells (anti-CD19 versus sideward scatter); gating of CD21low B cells (anti-CD38 versus anti-CD21); gating of IgD-IgM- and IgM+ B cells (anti-IgD versus anti-IgM). Pre-gated IgD-IgM- B cells were further used to identify plasmablasts (CD27+CD38high) and class-switched memory B cells (CD27+CD38low), pre-gated IgM+ B cells were used to identify of class non-switched memory B cells (CD27+CD38low), and the pre-gated IgM+CD27- B cells were used to identify transitional B cells (CD24+CD28high). WB, whole blood.