Fig. 4

Sex differences in the percentages of IRF5 positive CD20 + IgD–IgM + immature B cells and but not of IRF5 positive CD20 + IgD + IgM + mature naïve B cells. A Flow cytometric plots showing the applied gating strategy for IgD–IgM + , and IgD + IgM + B cells in a representative woman and man (out of 22 experiments). B cells were purified with Human B Cell Enrichment Cocktail. Gates distinguishing IgD + and IgD-cells were set plotting IgD against the side scatter (SSC-A) on B cells, as this enabled a clear distinction of IgD positive and negative B cell populations. Percentages of IRF5 positive cells were analyzed ex vivo by flow cytometry. IRF5 positive cells (in blue) were determined by the use of an isotype control (in red). B Left: under unstimulated conditions, women showed significantly higher percentages of IRF5 positive CD20 + IgD–IgM + immature B cells than men (p = 0.01; two-tailed t test; women n = 11, men n = 11). The percentage of IRF5 positive CD20 + IgD + IgM + mature naïve B cells in women was only slightly higher than the percentage of IRF5 positive CD20 + IgD + IgM + mature naïve B cells in men. Right: after 20 h of stimulation with the TLR9 agonist CpG (ODN 2216), women still showed a significantly higher percentages of IRF5 positive CD20 + IgD–IgM + immature B cells compared to those of men (p = 0.03; two-tailed t test; women n = 11, men n = 11). No significant differences in the percentages of IRF5 positive CD20 + IgD + IgM + mature naïve B cells were observed between the sexes. Pink dots indicate women, blue dots indicate men donors