As we age, we become increasingly vulnerable to cancer, infection and autoimmune disease.
Because of our declining ability to mount an aggressive immune response, and an increase in mistakes in our immune function towards the end of our life span, we are much more prone to dying from pneumonia or influenza over the age of 65.
We’re also facing a tougher fight against cancer, as it is the immune system that plays a role in the first defense by identifying and destroying aberrant cancer cells.
The term coined to describe changes that occur in the immune system as we age is called immunosenescence. Some of these changes include the shrinking of the bone marrow, where precursor immune cells are formed.
The thymus gland, which plays a role in producing T-cell lymphocytes, disappears, while chronic viral infections such as Cytomegalovirus produce a state of chronic inflammation that fatigues the immune system and taxes the remaining immune cells.
Their efforts to replicate and fight infection erode the protective caps on either end of their chromosomes, known as telomeres, which result in replication mistakes that can lead to aberrant cancerous cells.
The immune system of the elderly is sluggish in responding to novel microbial invaders it has never seen before. This is why the influenza vaccine is not as effective in elderly people. Interestingly, the memory cells in the immune system formed in response to infections or vaccines we were exposed to earlier in life, are relatively well-preserved. For example, survivors of the swine flu epidemic of 1918 were relatively protected against the H1N1 influenza pandemic of 2009. Vaccines given at a timely point in the life cycle are protective for life.
Medical science is starting to identify some of the underlying causes for immunosenescence, as well as possible ways of measuring immune function. One promising test is the Leukocyte (white blood cell) Telomere Length. While there will no doubt be a role for certain drugs and hormones to boost the immune system in the future, none have been sufficiently studied to the extent they can be recommended at this time. Stay tuned – human longevity is subject to ongoing research and scrutiny to enhance our immune systems.