B-cell immunophenotyping. B-cell immunophenotyping of 13 patients. Gray boxes indicate the normal age-related ranges for relative B-cell counts. (A) Naïve B cells (CD19⁺IgD⁺CD27⁻). (B-C) Nonswitched memory (CD19⁺IgD⁺CD27⁺) and switched memory B cells (CD19⁺IgD⁻CD27⁺) were reduced in 69% and 54% of the patients, respectively. (D) One patient (P12), suffering from EBV-related mixed B- and T-cell lymphoproliferative disease, showed an accumulation of transitional B cells (CD19⁺IgM⁺⁺CD38⁺⁺). (E-F) Exhausted B cells (CD19⁺IgM^loCD38^lo) and plasmablasts (CD19⁺IgM^loCD38⁺⁺) were normal in most of the cases.