The+ageing+immune+system-is+it+ever+too+old+to+become+young+again

The ageing immune system-is it ever too old to become young again

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The ageing immune system-is it ever too old to become young again

elderly people are particularly susceptible to influenza, with 80–90% of mortalities from infection with influenza virus occurring in individuals aged 65 years and older 3.

Elderly individuals also suffer from autoim- munity more frequently, which further indicates the dysregulation of immune- system function that can occur with age4.

Although the production of new T cells declines significantly with age, the thymus still has limited activity even in individuals of almost 100 years of age8.

For example, B cells from aged humans produce antibodies with decreased affinity for antigen and have an impaired ability to undergo class-switch recombination com- pared with B cells from younger individu- als16.

the CD8+ T-cell repertoire becomes increasingly skewed towards previously encountered antigens, particularly those derived from cytomegalovirus19,20.

B-cell acute lymphoblastic leukaemia is the most common type of paediatric cancer 27

haematopoietic stem cells (HSCs) from old animals have Nature Reviews | compared with downregulated expression of genes that control immune-cell development Immunology HSCs from young animals59. A challenge will be to identify those genes that act at crucial checkpoints at which multiple intracellular pathways converge, as these are likely to be the most promising targets for preventing or reversing immune-cell ageing.

An obvious example is the case of vaccina- tion against influenza virus, which has an efficacy of only 30–40% in protecting elderly patients from disease34

caloric restriction both pros and cons here's a pro caloric restriction increases the number of naive T cells and the diversity of the T-cell repertoire38,39

here's a con aged mice on a regimen of caloric restriction have increased mortality in response to influenza virus because they lack the energy reserves that are required to respond to the infection40

cytokine and hormone treatment

it will be interesting to see if advances in the field of stem-cell biology will be applicable to immune-system ageing 47

useful to have simple biomarkers with which to accurately measure the effects of ageing on the immune system. Progress in this area is already apparent; for example, the loss of CD28 expression by senescent CD8+ T cells correlates with a decreased response to vaccination52. It is also interesting that ageing is associated with an increased level of circulating, pro-inflammatory cytokines, such as Il-6.