B cells lacking TRAF2, TRAF3 or cIAP1 plus cIAP2 no longer require BAFF-R for their in vivo development and survival. Traf2ΔB, Traf3ΔB, and cIap1ΔB.cIap2−/− mice were crossed onto a BAFF-R–deficient (Tnfrsf13c−/−) background. Flow cytometric analysis of (A) lymph node or (B) spleen from the indicated mice lines. Windows indicate immature (B220+, AA4.1+) and mature (B220+, AA4.1−) phenotype B cells. Data in CD21 versus CD23 and CD21 versus CD1 days profiles are from total B cells (B220+ gate), and windows show immature (CD21/CD35lo, CD23lo), follicular (CD21/CD35mid, CD23hi), and marginal zone (CD21/CD35hi, CD23lo and CD21/CD35hi, CD1 dayshi) B-cell populations. All numbers indicate the proportion of displayed events falling within the associated windows.