Interleukin-7 responsiveness of B220+ B cell precursors from bone marrow decreases in aging mice.

Using short-term culture assays to quantify the activity of B220+ B cell progenitors from bone marrow of young and old mice, we observed a decrease with age in the ability of B220+ cells in bone marrow to proliferate in IL-7. Dose-response curves showed no difference between young and old mice in the amount of IL-7 required to stimulate B220+ cells. However, the B220+ cells from the bone marrow of old donors (> 20 weeks) contained two- to fivefold fewer cells responsive to IL-7 than the identical cell population isolated from young donors. Similar results were obtained with mice up to 48 weeks of age from three different strains, BALB/c, C57BL/6, and C.B-17. These data provide evidence for a small, but reproducible, age-associated decrease in B cell production.