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Studies on the mechanism of low natural killer cell activity in infant and aged mice
Insights
Natural killer (NK) cell activity in mice decreases with age due to suppressor cells and a deficiency in NK cell precursors in infants. Older mice show restored NK activity, indicating complex age-related regulatory mechanisms.
Area of Science:
- Immunology
- Aging Research
Background:
- Natural killer (NK) cell activity in mice exhibits significant age-related variation, being high in young adults (6-10 weeks) and low in infants and aged mice (>12-14 weeks).
- Understanding the mechanisms behind this age-dependent regulation of NK cell function is crucial for insights into immune senescence and development.
Purpose of the Study:
- To investigate the underlying mechanisms responsible for the characteristic age-related decline and recovery of NK cell activity in mice.
- To compare the NK cell activity regulation in infant and aged mice relative to young adult mice.
Main Methods:
- Assessing NK cell activity following incubation with interferon (IFN) and interleukin-2 (IL-2) in spleen cells from infant, young, and old mice.
- Utilizing limiting dilution assays to determine the frequency of IL-2-dependent NK cell progenitors.
- Analyzing the presence and characteristics of suppressor cells (plastic-adherent and nonadherent) in the spleens of mice across different age groups.
Main Results:
- Infant mouse spleen cells showed limited NK activity development upon stimulation with IFN or IL-2 and were deficient in NK cell precursors.
- Spleen cells from old mice (30 weeks) exhibited substantial NK activity upon stimulation and possessed a similar frequency of NK cell progenitors as young mice.
- Both infant and old mice had plastic-adherent suppressor cells that inhibited NK activity, and both age groups contained nonadherent suppressor cells with higher density than NK cells.
Conclusions:
- Age-related regulation of NK activity in mice is multifactorial, involving both developmental deficiencies and inhibitory mechanisms.
- Suppressor cell populations, both adherent and nonadherent, play a significant role in suppressing NK activity in infant and aged mice.
- While infant mice are deficient in NK cell precursors, aged mice retain progenitor potential but are affected by suppressive cellular environments.
Abstract:
NK activity in mice is high between about 6 and 10 weeks of age. In contrast, infant mice and mice older than 12-14 weeks of age usually have quite low or undetectable NK activity. Studies were performed to analyze the mechanisms underlying this characteristic age-related regulation of NK activity. Spleen cells from infant mice did not develop appreciable NK activity upon incubation for 12-18 h with either interferon (IFN) or interleukin-2 (IL-2). Analysis of the frequency of IL-2-dependent progenitors of NK cells, in a limiting dilution assay, also indicated that the spleens of infant mice are deficient in precursors of NK cells. In contrast, spleen cells from old mice (30 weeks old) developed substantial levels of NK activity upon incubation with either IFN or IL-2, and they showed a frequency of IL-2-dependent progenitors of effector cells that was similar to that of young mice. Both infant and old mice had plastic-adherent suppressor cells in their spleens, which could strongly inhibit NK activity. In addition, both infant and old mouse spleen cells contained nonadherent suppressor cells, which had a higher density on Percoll gradients than NK cells. Thus, several factors appear to contribute to the age-related regulation of NK activity in mice.