Population L in LMP1+TRAF5+/+ and LMP1+TRAF5−/− mice. Spleens were collected from LMP1−TRAF5+/+ (white bars), LMP1+TRAF5+/+ (black bars), and LMP1+TRAF5−/− (gray bars) mice of 3–4 months of age. The spleens were homogenized and stained with anti-B220 PerCp mAb, anti-CD21/35 FITC mAb, and anti-CD23 PE mAb (A) or anti-B220 PerCp mAb, anti-IgD FITC mAb, and anti-IgM PE mAb (B). *, P < 0.0001.