tailieunhanh - Blood Disorders in the Elderly - part 3

Cần nhấn mạnh rằng nghiên cứu như vậy tương ứng không trong bất kỳ cách nào đề nghị rằng nó là telomere rút ngắn thời gian cho mỗi gia nhập, đó là nguyên nhân gây ra tử vong. Thay vào đó, nó có nhiều khả năng là giảm chiều dài telomere là một biomarker thay đổi sinh lý khác | 88 Rita B. Effros of dying from infectious causes compared to those individuals with the longest telomeres 57 . It should be emphasized that such correlative studies do not in any way suggest that it is telomere shortening per se that is the cause of mortality. Rather it is more likely that the reduced telomere length is a biomarker of other physiological changes 58 . For example in the case of shorter telomeres being associated with increased death from infectious causes one possible mechanism that might be operating is that the T cells were working overtime and eventually failing to control a particular infection and in the process undergoing extensive cell division and concomitant telomere shortening. Studies on HIV-infected persons are consistent with this notion since over many years the chronic activation and proliferation of CD8 T cells does eventually lead to high proportions of CD8 T cells that lack CD28 expression and have shortened telomeres. An alternative possibility to explain the short-telomere infection association relates to the observation that telomere length is a heritable trait 59-61 and may be linked to other genetic factors that are the true cause of the increased death risk from infections. Given that infections are a major cause of morbidity and mortality in the elderly vaccination is an important prophylactic strategy. Influenza in particular has been shown to be the fourth leading cause of death in elderly persons so that this age group is a priority target population for influenza vaccination. Thus it is highly relevant that two studies have shown a significant correlation between poor response to influenza vaccination and high proportions of senescent CD8 T cells. The underlying mechanism for this association has not been identified but in other contexts CD8 T cells that lack CD28 expression have been shown to have suppressor cell functions leading to downregulation of antigen presentation as well as other T-cell activities 62 . CD8 .