Figure 1.

ATM mutations result in altered new emigrant and mature naive B cell population frequencies. A) B cells isolated from PBMC by anti-CD20 magnetic bead separation from a healthy donor (HD) control sample processed in parallel with the AT patient sample show similar frequencies of the CD19⁺CD20⁺CD27⁺ memory and CD19⁺CD20⁺CD27⁻ naive B cell compartments. B) Despite similar overall naive B cell compartment frequencies, the naive CD19⁺CD20⁺CD27⁻CD21⁻CD10⁺IgM^hi new emigrant B cell population transitioning from the bone marrow is decreased in the AT patient. C) Conversely, the mature naive B cell compartment in the AT patient contains an elevated frequency of atypical CD19⁺CD20⁺CD27⁻CD10⁻CD21^−/low B cells. D) This compartment in the AT patient exhibits elevated Fas expression and E) is enriched in TBET⁺ cells compared to lower Fas and TBET expression in the HD control (dashed histogram represents isotype control for both Fas and TBET).