CD21/35−CD23− B cells accumulate in aged mice. (A) Cells from spleen were first gated on CD19+ AA4.1− CD43− live single lymphocytes. Percentage of FO (CD21/35loCD23+), MZ (CD21/35hiCD23−), and novel B-cell (CD21/35−CD23−, ABC) subsets are shown in female C57BL/6 mice at age 3, 12, and > 22 months. (B) Absolute numbers of ABCs in spleen from mice at age 3, 12, and > 22 months; n = 3-5 mice and similar results were observed in 5 independent experiments. The Student t test was used for statistical analysis; **P < .01. (C) Expression of 10 surface markers on ABCs (dark bold) compared with FO (dotted) and MZ (dashed) B cells from 22-month-old mice. Light gray peaks represent negative controls and the black peak represents the positive control for CD5 on B1 B cells.
