Age-related changes in production of interleukin-7 (IL-7) by murine long-term bone marrow cultures (LTBMC)

Age-related decreases in humoral immune function have been well documented. In aged mice, these functional deficits may be due, in part, to decreased numbers of precursor B cells. Interleukin-7 (IL-7) plays a key role in B cell development by stimulating proliferation of progenitor and pre-B cells. In the current study, proliferation of the murine IL-7-dependent pre-B cell line SCID/FC-7 (SCID) was used to assess IL-7 activity in long-term bone marrow culture-conditioned medium (LTBMC-CM) from both young (4-8-week-old) and older (16-40-week-old) mice. Time to reach peak production and peak IL-7 levels were similar in both groups and was optimal between weeks 2 and 6 of culture. IL-7 activity in LTBMC-CM from older mice fell rapidly to negligible levels after 8 weeks in culture. These findings are consistent with age-related changes in stem cell production and B lymphopoiesis in LTBMC reported in other studies.