IgM⁺IgD⁺CD27⁺ cells are significantly decreased in IRAK-4–, MyD88-, and TIRAP-deficient patients. (A) Relative frequencies of blood IgD⁺CD27⁺ and IgD⁻CD27⁺ cells (expressed as percentages of CD19⁺ B cells) in IRAK-4–, MyD88-, TIRAP-, UNC-93B–, and TLR3-deficient patients and controls were determined by flow cytometry after IgD, CD27, and CD19 staining. Only values from patients or control patients older than 4 years of age were plotted (ie, excluding the 3.5-year-old TRIF-deficient patient, as well as patients P30 [IRAK-4, 2 years] and P2 [MyD88, 2 years]). Mean values (expressed as percentage of total B cells) are indicated below the graph for IRAK-4–, MyD88-, and TIRAP-deficient patients and controls. *P < .05, **P < .01, ***P < .001 (see “Methods” for statistics). (B) Ratio of the IgM⁺IgD⁺CD27⁺ versus IgD⁻CD27⁺ cell proportions for all the patients and controls (from 2 to 25 years of age).