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Aging and developmental transitions in the B cell lineage
Kara M Johnson1, Kevin Owen, Pamela L Witte
1Departments of Microbiology and Immunology, Loyola University Medical Center, Maywood, IL 60153, USA.
International Immunology
|October 31, 2002
Summary
Aging impairs the immune system by reducing new B cell production in elderly individuals. Despite fewer pre-B cells, the rate of immature B cell production remains unchanged, suggesting a peripheral replenishment issue.
Area of Science:
- Immunology
- Gerontology
- Hematology
Background:
- Humoral immune response declines in elderly individuals.
- B lymphopoiesis (B cell production) may decrease with age.
- Pre-B cell numbers significantly drop in aged mice, but mature B cell numbers remain stable.
Purpose of the Study:
- To investigate B cell production rates in young and old mice.
- To determine if new B cells are generated in aged animals despite reduced pre-B cells.
- To elucidate the cause of diminished humoral immunity in aging.
Main Methods:
- Utilized 5'-bromo-2-deoxyuridine (BrdU) labeling to track B cell production.
- Analyzed B cell production rates in bone marrow and spleen of young and old mice.
- Acquired data from over 60 young and 50 old mice due to variability in aged mice.
Main Results:
- Transitional and mature B cell compartments in the spleen showed slower labeling kinetics in old mice.
- Newly produced B cells constituted 15% of the mature B cell compartment in old mice versus 30% in young mice after 4 weeks.
- No statistical difference was found in the production rate of new immature B cells in the bone marrow between young and old animals.
Conclusions:
- B lymphopoiesis rate in the bone marrow does not decline with age.
- Mature B cells in old mice exhibit slower turnover.
- The defect in mature B cell turnover is attributed to an inability of newly produced B cells to replenish peripheral compartments, not a decline in B lymphopoiesis.