Anti- XXXX -induced apoptosis in T-cells from young and old @entity19 .

@entity19 @entity1961 @entity5168
Light scatter measurements using flow cytometry indicated that T cells from young and old @entity19 undergo apoptosis following activation with immobilized anti- @entity5168 . The percentage of cells in apoptosis after 20 h activation was significantly greater (p < .001) in cultures containing cells from older animals. The mean percentages of apoptotic T cells from young and old @entity19 after 20 h activation were 19.3% and 33.0%, respectively. The proportion of viable cells after 20 h activation was significantly higher (p < .003) in the young (mean = 78.4%) than in the old animals (mean = 65.8%). Simultaneous measurements of light scatter and fluorescence indicated that apoptotic T cells contained both the @entity1961 + and the CD8+ T-cell phenotypes. The frequency of apoptotic CD8+ T cells was elevated (p < .007) in older animals, where the mean percentage was 15.1%, compared to 5.3% in the young. The most dramatic difference between young and old (p < .0008) was seen in the percentages of viable @entity1961 + T cells after 20 h activation. The mean viable @entity1961 + T-cell percentage was 33.7% in- the young and 21.4% in the old. @entity1961 + cells expressing high levels of CD45RB (CD45RBhi) after activation for 20 h possessed light scatter and bright fluorescence properties characteristic of viable cells, whereas @entity1961 +/CD45RBlo density cells could be identified as apoptotic based on their decreased @entity1961 fluorescence and scatter characteristics. @entity1961 + cells from young animals were predominantly CD45RBhi, whereas @entity1961 + cells from the old had greater levels of CD454RBlo cells. In addition to light scatter changes, measurement of DNA content after 40 h activation revealed the presence of a sub-G1 DNA apoptotic peak and a viable cell cycle distribution. After 40 h of activation, there was an increase in the percentage of apoptotic cells in both young and old @entity19 , with the greatest increase seen in the cells from older animals. Further evidence supporting the process of apoptosis in 40 h-activated cells was confirmed by the appearance of DNA strand breaks detected by in situ nick translation.
