Bone marrow B cells TgE Notch^lox/lox CD19^+/Cre mice have a decreased survival capacity in low IL-7. Equal numbers of B220⁺ cells harvested from methylcellulose cultures were plated in either high IL-7 or low IL-7. At 48 hours, cells were analyzed by flow cytometry to determine the cell recovery. The percentage of cells in the live cell gate, based on forward and side scatter properties, was recorded and graphed as relative survival compared with high IL-7 for each genotype. We have demonstrated previously that relative survival inversely correlates with apoptosis as measured by annexin V binding.¹⁹  Results are the average of 3 independent experiments after 48 hours plus or minus SE. *P = .002 by t test. Notch1^lox/lox, n = 4 mice; Notch1^lox/lox CD19^+/Cre, n = 3; TgE Notch1^lox/lox, n = 5; TgE Notch1^lox/lox CD19^+/Cre, n = 6.