PS exposure on B cells from CD45^-/- and parental mice. (A) Lymphocytes from CD45^-/- (solid line) or parental (CD45^+/+) mice (dotted line) were labeled with anti-CD19^APC and anti-CD19^PE antibodies, respectively, to discriminate between CD19⁺ B cells from each mouse after mixing. Cells were mixed and preincubated with AV^FITC to assess PS exposure. (B) To compare the rate of cell death among spleen cells from parental (C57BL/6) and CD45^-/- mice, the sub-G₁ DNA content of lymphocytes at t = 0 and 24 hours was assessed through uptake of propidium iodide (PI) analyzed by flow cytometry. Percentages of cells containing sub-G₁ levels of DNA are shown. (C) Lymphocytes from CD45^-/- (gray line) or parental (CD45^+/+) mice (black line) were labeled with anti-CD19^APC and anti-CD19^FITC antibodies, respectively, to discriminate between CD19⁺ B cells from each mouse, mixed, and incubated with MC540 to assess lipid packing.